Journal articles: '4H-SiC'

1

Shilpa, A., S. Singh, and N. V. L. Narasimha Murty. "Spectroscopic performance of Ni/4H-SiC and Ti/4H-SiC Schottky barrier diode alpha particle detectors." Journal of Instrumentation 17, no. 11 (November 1, 2022): P11014. http://dx.doi.org/10.1088/1748-0221/17/11/p11014.

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Abstract Advancement in the growth of 4H-SiC with low micropipe densities (∼ 0.11 cm-2) in achieving high pure epitaxial layers, enabled the development of high-resolution 4H-SiC alpha particle Schottky radiation detectors for harsh environments. In particular, the study considers two types of 4H-SiC radiation detectors having Ni and Ti as Schottky contacts. They are fabricated by depositing Ni and Ti on 25 μm thick n-type 4H-SiC by epitaxially growing on 350 μm thick conducting SiC substrates. Electrical characterization and alpha spectral measurements performed on Ni/4H-SiC and Ti/4H-SiC SBDs are reported in this work. The spectral measurements were carried out using 241Am alpha emitting radioactive source. Ni/ 4H-SiC Schottky detector showed a better spectral response with 22.87 keV FWHM (∼ 0.416%) at a reverse bias of 150 V for 5.48 MeV alpha particles while Ti/4H-SiC Schottky detector achieved a resolution of 38.25 keV FWHM (∼ 0.697%) at 170 V reverse bias. This work presented spectral broadening analysis to understand the various factors affecting the energy resolution of the detectors. The extracted charge collection efficiencies (CCEs) are approximately 99% in both the detectors. In addition, polarization effects are not noticed in any of the fabricated detectors. The diffusion length of minority carriers (Lp ) is computed based on the drift-diffusion model by fitting the CCE curve as a function of applied bias, and the values are close to 9 μm and 7 μm for Ni/4H-SiC SBD and Ti/4H-SiC SBD detectors, respectively. Annealing at 400°C for 5 minutes in N2 ambient resulted in resolution of 23.98 keV FWHM (∼ 0.436%) for Ni/4H-SiC SBD detector at -170 V and 36.21 keV FWHM (∼ 0.661%) for Ti/4H-SiC SBD detector at -150 V. Overall Ni/4H-SiC SBD detectors showed superior spectral characteristics and superior resolution when compared to Ti/4H-SiC SBD detectors. However, the Ti/4H-SiC SBD detector fabricated in this work performed better than the previously reported work on a similar device structure. Hence, future work aimed at improving resolution of radiation detectors could also consider Ti/4H-SiC SBDs along with Ni/4H-SiC SBDs.

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Yoneda, S., Tomoaki Furusho, H. Takagi, S. Ohta, and Shigehiro Nishino. "Homoepitaxial Growth on 4H-SiC (03-38) Face by Sublimation Close Space Technique." Materials Science Forum 483-485 (May 2005): 129–32. http://dx.doi.org/10.4028/www.scientific.net/msf.483-485.129.

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For preliminary step toward fabrication of MOSFET using 4H-SiC 8) 3 (03 prepared by sublimation method, epitaxial growth of device quality 4H-SiC on 4H-SiC (0001) 8.0° off substrate was carried out and investigated. Smooth and specular surface of 4H-SiC (0001) plane was obtained by optimum growth condition. And epitaxial growth on 4H-SiC 8) 3 (03 and ) 8 3 (03 substrates were carried out with optimum growth conditions of 4H-SiC (0001). Smooth and specular surface was obtained on 4H-SiC 8) 3 (03 and ) 8 3 (03 plane. Growth rate of epilayers of 4H-SiC (0001), 8) 3 (03 and ) 8 3 (03 face were same. Oxidation rate of 4H-SiC (0001), ) 1 (000 , 8) 3 (03 and ) 8 3 (03 face was investigated. The oxidation rate was different depending on the faces. It was observed that the difference of oxidation rate of 8) 3 (03 and ) 8 3 (03 is mainly due to the difference of polarity similar to the case of reported for (0001) and ) 1 (000 .

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Yang, Guang, Hao Luo, Jiajun Li, Qinqin Shao, Yazhe Wang, Ruzhong Zhu, Xi Zhang, et al. "Discrimination of dislocations in 4H-SiC by inclination angles of molten-alkali etched pits." Journal of Semiconductors 43, no. 12 (December 1, 2022): 122801. http://dx.doi.org/10.1088/1674-4926/43/12/122801.

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Abstract Discrimination of dislocations is critical to the statistics of dislocation densities in 4H silicon carbide (4H-SiC), which are routinely used to evaluate the quality of 4H-SiC single crystals and homoepitaxial layers. In this work, we show that the inclination angles of the etch pits of molten-alkali etched 4H-SiC can be adopted to discriminate threading screw dislocations (TSDs), threading edge dislocations (TEDs) and basal plane dislocations (BPDs) in 4H-SiC. In n-type 4H-SiC, the inclination angles of the etch pits of TSDs, TEDs and BPDs in molten-alkali etched 4H-SiC are in the ranges of 27°−35°, 8°−15° and 2°−4°, respectively. In semi-insulating 4H-SiC, the inclination angles of the etch pits of TSDs and TEDs are in the ranges of 31°−34° and 21°−24°, respectively. The inclination angles of dislocation-related etch pits are independent of the etching duration, which facilitates the discrimination and statistic of dislocations in 4H-SiC. More significantly, the inclination angle of a threading mixed dislocations (TMDs) is found to consist of characteristic angles of both TEDs and TSDs. This enables to distinguish TMDs from TSDs in 4H-SiC.

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Furusho, Tomoaki, Ryota Kobayashi, Taro Nishiguchi, M. Sasaki, K. Hirai, Toshihiko Hayashi, Hiroyuki Kinoshita, and Hiromu Shiomi. "Growth of Micropipe Free Crystals on 4H-SiC {03-38} Seeds." Materials Science Forum 527-529 (October 2006): 35–38. http://dx.doi.org/10.4028/www.scientific.net/msf.527-529.35.

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Growth of 4H-SiC bulk crystals on 4H-SiC {03-38} seeds was done. 4H-SiC {03-38} is obtained by inclining the c-plane toward <01-10> at a 54.7 degrees angle. Growth on the 4H-SiC {03-38} seed has the potential to achieve high quality crystals without micropipes and stacking faults. Micropipe-free c-plane 4H-SiC wafers were achieved by growth on the 4H-SiC {03-38} seed. A transmission X-ray topograph image of the micropipe free c-plane wafer revealed that there are no macroscopic defects with displacements.

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Alexander, Kazuaki Seki, Shigeta Kozawa, Yuji Yamamoto, Toru Ujihara, and Yoshikazu Takeda. "Polytype Stability of 4H-SiC Seed Crystal on Solution Growth." Materials Science Forum 679-680 (March 2011): 24–27. http://dx.doi.org/10.4028/www.scientific.net/msf.679-680.24.

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We investigated the polytype transition process from 4H-SiC to 6H-SiC during solution growth from the viewpoint of growth mode. The polarity dependence of the dominant grown polytype was similar to those of the sublimation growth and the CVD growth that 4H-SiC relatively grew stably on the C-face. Moreover, the polytype transition occurred during spiral growth. The 6H-SiC expanded to periphery overgrowing on the 4H-SiC. In contrast, there is no sign that 4H-SiC grew on 6H-SiC.

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6

Naik, Harsh, and T. Paul Chow. "Comparison of Inversion Electron Transport Properties of (0001) 4H and 6H-SiC MOSFETs." Materials Science Forum 679-680 (March 2011): 678–81. http://dx.doi.org/10.4028/www.scientific.net/msf.679-680.678.

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The effect of using two different polytypes, 4H-SiC and 6H-SiC, on the performance of (0001) SiC MOSFETs has been studied. 4H-SiC and 6H-SiC MOSFETs have been fabricated with deposited gate oxides followed by oxidation in dry O2 or NO. Device parameters, particularly field-effect mobility, inversion sheet carrier concentration and Hall mobility have been extracted. We have also compared the mobility-limiting mechanisms of (0001) 4H and 6H-SiC MOSFETs and found that inversion mobility can be further improved in 4H-SiC, but not 6H-SiC.

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Moon, Jeong Hyun, Da Il Eom, Sang Yong No, Ho Keun Song, Jeong Hyuk Yim, Hoon Joo Na, Jae Bin Lee, and Hyeong Joon Kim. "Electrical Properties of the La₂O₃/4H-SiC Interface Prepared by Atomic Layer Deposition Using La(iPrCp)₃ and H₂O." Materials Science Forum 527-529 (October 2006): 1083–86. http://dx.doi.org/10.4028/www.scientific.net/msf.527-529.1083.

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The La2O3 and Al2O3/La2O3 layers were grown on 4H-SiC by atomic layer deposition (ALD) method. The electrical properties of La2O3 on 4H-SiC were examined using metal-insulator-semiconductor (MIS) structures of Pt/La2O3(18nm)/4H-SiC and Pt/Al2O3(10nm)/La2O3(5nm)/4H-SiC. For the Pt/La2O3(18nm)/4H-SiC structure, even though the leakage current density was slightly reduced after the rapid thermal annealing at 500 oC, accumulation capacitance was gradually increased with increasing bias voltage due to a high leakage current. On the other hand, since the leakage current in the accumulation regime was decreased for the Pt/Al2O3/La2O3/4H-SiC MIS structure owing to the capped Al2O3 layer, the capacitance was saturated. But the saturation capacitance was strongly dependent on frequency, indicating a leaky interfacial layer formed between the La2O3 and SiC during the fabrication process of Pt/Al2O3(10nm)/ La2O3(5nm)/ 4H-SiC structure.

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8

Kinoshita, Akimasa, Takasumi Ohyanagi, Tsutomu Yatsuo, Kenji Fukuda, Hajime Okumura, and Kazuo Arai. "Fabrication of 1.2kV, 100A, 4H-SiC(0001) and (000-1) Junction Barrier Schottky Diodes with Almost Same Schottky Barrier Height." Materials Science Forum 645-648 (April 2010): 893–96. http://dx.doi.org/10.4028/www.scientific.net/msf.645-648.893.

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It is known that a Schottky barrier height (b) of metal/C-face 4H-SiC Schottky barrier diode (SBD) differ from b of metal/Si-face 4H-SiC SBD. Furthermore, b of metal/4H-SiC SBD varies with annealing temperature. We fabricate 0.231mm2 SBD with Ti/SiC interface using Si-face and C-face 4H-SiC. These SBDs are annealed at several temperatures after a formation of the Ti/SiC interface. As a result, b of Ti/C-face 4H-SiC interface annealed at 400 oC is nearly equal to b of Ti/Si-face 4H-SiC interface annealed at 500 oC and the n-values of these SBDs are nearly equal to the ideal value (unity). Using that annealing condition, we fabricated 25mm2 junction barrier Schottky (JBS) diodes with Ti/SiC interface on Si-face and C-face 4H-SiC epitaxial substrate. b of Si-face and C-face JBS diodes are 1.26eV and 1.24eV, respectively. The leakage currents for both Si-face and C-face JBS diodes are less than 1mA/cm2. The current of 100A is obtained at the forward bias voltage of 1.95V and 2.16V for the Si-face JBS and the C-face JBS.

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9

Shao, Shi Qian, Wei Cheng Lien, Ayden Maralani, Jim C. Cheng, Kristen L. Dorsey, and Albert P. Pisano. "4H-Silicon Carbide p-n Diode for High Temperature (600 °C) Environment Applications." Materials Science Forum 821-823 (June 2015): 636–39. http://dx.doi.org/10.4028/www.scientific.net/msf.821-823.636.

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In this work, we demonstrate the stable operation of 4H-silicon carbide (SiC) p-n diodes at temperature up to 600 °C. In-depth study methods of simulation, fabrication and characterization of the 4H-SiC p-n diode are developed. The simulation results indicate that the turn-on voltage of the 4H-SiC p-n diode changes from 2.7 V to 1.45 V as the temperature increases from 17 °C to 600 °C. The turn-on voltages of the fabricated 4H-SiC p-n diode decreases from 2.6 V to 1.3 V when temperature changes from 17 °C to 600 °C. The experimental I-V curves of the 4H-SiC p-n diode from 17 °C to 600 °C agree with the simulation ones. The demonstration of the stable operation of the 4H-SiC p-n diodes at high temperature up to 600 °C brings great potentials for 4H-SiC devices and circuits working in harsh environment electronic and sensing applications.

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10

Xu, Bei, Changjun Zhu, Xiaomin He, Yuan Zang, Shenghuang Lin, Lianbi Li, Song Feng, and Qianqian Lei. "First-Principles Calculations on Atomic and Electronic Properties of Ge/4H-SiC Heterojunction." Advances in Condensed Matter Physics 2018 (2018): 1–9. http://dx.doi.org/10.1155/2018/8010351.

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First-principles calculation is employed to investigate atomic and electronic properties of Ge/SiC heterojunction with different Ge orientations. Based on the density functional theory, the work of adhesion, relaxation energy, density of states, and total charge density are calculated. It is shown that Ge(110)/4H-SiC(0001) heterointerface possesses higher adhesion energy than that of Ge(111)/4H-SiC(0001) interface, and hence Ge/4H-SiC(0001) heterojunction with Ge[110] crystalline orientation exhibits more stable characteristics. The relaxation energy of Ge(110)/4H-SiC(0001) heterojunction interface is lower than that of Ge(111)/4H-SiC(0001) interface, indicating that Ge(110)/4H-SiC(0001) interface is easier to form at relative low temperature. The interfacial bonding is analysed using partial density of states and total charge density distribution, and the results show that the bonding is contributed by the Ge-Si bonding.

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11

Sun, Guo Sheng, Yong Mei Zhao, Liang Wang, Lei Wang, Wan Shun Zhao, Xing Fang Liu, Gang Ji, and Yi Ping Zeng. "In Situ Boron and Aluminum Doping and Their Memory Effects in 4H-SiC Homoepitaxial Layers Grown by Hot-Wall LPCVD." Materials Science Forum 600-603 (September 2008): 147–50. http://dx.doi.org/10.4028/www.scientific.net/msf.600-603.147.

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The in-situ p-type doping of 4H-SiC grown on off-oriented (0001) 4H-SiC substrates was performed with trimethylaluminum (TMA) and/or diborane (B2H6) as the dopants. The incorporations of Al and B atoms and their memory effects and the electrical properties of p-type 4H-SiC epilayers were characterized by secondary ion mass spectroscopy (SIMS) and Hall effect measurements, respectively. Both Al- and B-doped 4H-SiC epilayers were p-type conduction. It was shown that the profiles of the incorporated boron and aluminum concentration were in agreement with the designed TMA and B2H6 flow rate diagrams. The maximum hole concentration for the Al doped 4H-SiC was 3.52×1020 cm-3 with Hall mobility of about 1 cm2/Vs and resistivity of 1.6~2.2×10-2 Wcm. The heavily boron-doped 4H-SiC samples were also obtained with B2H6 gas flow rate of 5 sccm, yielding values of 0.328 Wcm for resistivity, 5.3×1018 cm-3 for hole carrier concentration, and 7 cm2/Vs for hole mobility. The doping efficiency of Al in SiC is larger than that of B. The memory effects of Al and B were investigated in undoped 4H-SiC by using SIMS measurement after a few run of doped 4H-SiC growth. It was clearly shown that the memory effect of Al is stronger than that of B. It is suggested that p-type 4H-SiC growth should be carried out in a separate reactor, especially for Al doping, in order to avoid the join contamination on the subsequent n-type growth. 4H-SiC PiN diodes were fabricated by using heavily B doped epilayers. Preliminary results of PiN diodes with blocking voltage of 300 V and forward voltage drop of 3.0 V were obtained.

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12

Sinelnik, A. V., and A. V. Semenov. "Theoretical study of the band structure of 2H-SiC and 4H-SiC of silicon carbide polytypes." Condensed Matter Physics 24, no. 2 (2021): 23706. http://dx.doi.org/10.5488/cmp.24.23706.

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We have studied the electronic band properties of 2H-SiC and 4H-SiC silicon carbide polytypes. The structures of the electronic bands and density of state (DOS) using ab initio Density Functional Theory (DFT) were calculated for the first Brillouin zone both in the generalized gradient approximation and taking into account quasiparticle effects according to the GW scheme. The calculated bandgaps obtained using the GW approximation Eg2H-SiC = 3.17 eV and Eg4H-SiC = 3.26 eV agree well with experimental values. The shape and values of total DOS are within agreement with calculations performed by other authors. The calculated total energy values for 2H-SiC and 4H-SiC were close, but they satisfy the condition E2H > E4H, which implies that the 4H-SiC structure is more stable than 2H-SiC. Our calculations of the band structure and DOS of 2H-SiC and 4H-SiC by the DFT method showed that the application of the GW approximation is an optimum approach to the study of the electronic structure of 2H-SiC and 4H-SiC polytypes.

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13

Tupitsyn, Eugene Y., Arul Arjunan, Robert T. Bondokov, Robert M. Kennedy, and Tangali S. Sudarshan. "A Study of 6H-Seeded 4H-SiC Bulk Growth by PVT." Materials Science Forum 483-485 (May 2005): 21–24. http://dx.doi.org/10.4028/www.scientific.net/msf.483-485.21.

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4H-SiC crystals were grown using the seeded sublimation technique (modified Lely technique) in the temperature range of 1950-2200°C. The nucleation of 4H-SiC on 6HSiC has been optimized and 4H-SiC crystals of 1cm thickness were grown using 6H-SiC seeds. a-face and c-face wafers obtained from the grown boules were characterized by KOH etching, X-ray diffraction, and Raman scattering studies. Complete polytypic homogeneity of 4H SiC was obtained during growth and it was found that the 6H to 4H transition occurs in three ways: 1) without a transition layer, 2) with thick 6H-SiC layer growth, and 3) with traces of 3C SiC inclusions. The crown regions of the grown crystals exhibit an X-ray rocking curve width of 21 arcsecs.

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14

Tu, Rong, Chengyin Liu, Qingfang Xu, Kai Liu, Qizhong Li, Xian Zhang, Marina L. Kosinova, Takashi Goto, and Song Zhang. "Epitaxial Growth of SiC Films on 4H-SiC Substrate by High-Frequency Induction-Heated Halide Chemical Vapor Deposition." Coatings 12, no. 3 (March 2, 2022): 329. http://dx.doi.org/10.3390/coatings12030329.

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SiC epitaxial wafers offer enormous potential for a wide range of telecom technologies due to their excellent properties. The experimental process was simulated by software, and the contour of gas flow velocity and raw material mass fraction inside the chamber were obtained. SiC films were epitaxially grown on 4H-SiC single crystalline substrates at different temperatures for one batch, using SiCl4, CH4, and H2 as precursors. With increasing temperature, the crystal phase changed from 4H-SiC at 1773 K to a mixture of 4H- and 3C-SiC, and then a mixture of 3C-SiC and graphite at higher than 1923 K. The film was mainly (004)-oriented 4H-SiC and (111)-oriented 3C-SiC.

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Zhang, Mengyu, Jingtao Huang, Xiao Liu, Long Lin, and Hualong Tao. "Electronic Structure and High Magnetic Properties of (Cr, Co)-codoped 4H–SiC Studied by First-Principle Calculations." Crystals 10, no. 8 (July 23, 2020): 634. http://dx.doi.org/10.3390/cryst10080634.

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The electronic structure and magnetic properties of 3d transition metal (Cr, Co)-codoped 4H–SiC were studied by density functional theory within GGA methods. The results show that all doped magnetic atoms have high magnetic properties in both Cr-doped and Co-doped 4H–SiC, resulting in the net magnetic moments of 3.03, 3.02 μ B for Si 35 CrC 36 and Si 35 CoC 36 . The electronic density of states reaches the peak at Fermi level, which is beneficial to the electronic transitions, indicating that Cr-doped 4H–SiC is a semi-metallic material. In addition, the magnetic properties of (Cr, Co)-codoped 4H–SiC were also calculated. The results show that the (Cr, Co)-codoped 4H–SiC system has more stable ferromagnetic properties with ΔE F M of −244.3 meV, and we estimated T C of about 470.8 K for the (Cr, Co)-codoped 4H–SiC system. The (Cr, Co)-codoped 4H–SiC can be ferromagnetic through some mechanism based on hybridization between local Cr:3d, Co:3d and C:2p states. These interesting discoveries will help promote the use of excellent SiC-based nanomaterials in spintronics and multi-function nanodevices in the near future.

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Громова, П. С., and Г. Г. Давыдов. "ОСОБЕННОСТИ РАДИАЦИОННОГО ПОВЕДЕНИЯ ВЫСОКОВОЛЬТНЫХ ПОЛУПРОВОДНИКОВЫХ ПРИБОРОВ НА 4H-SIC ПО ЭФФЕКТАМ НАКОПЛЕННОЙ ДОЗЫ И ОДИНОЧНЫМ ЭФФЕКТАМ ОТКАЗОВ." NANOINDUSTRY Russia 96, no. 3s (June 15, 2020): 609–11. http://dx.doi.org/10.22184/1993-8578.2020.13.3s.609.611.

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Экспериментально определена область безопасной работы высоковольтных диодов Шоттки на структурах 4H-SiC иностранного производства. Исследована деградация 4H-SiC изделий при воздействии накопленной дозы ионизирующего излучения. Проведено сравнение с аналогичными данными для высоковольтных приборов кремния. The paper highlights safe operating area for several types of high-voltage 4H-SiC Schottky diodes. Degradation of electrical parameters has been studied experimentally for several types of 4H-SiC power devices. Comparison with Si power devices has been carried out.

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Kusunoki, Kazuhiko, Kazuhito Kamei, Nobuyoshi Yashiro, Koji Moriguchi, and Nobuhiro Okada. "Crystal Growth of 4H-SiC on 6H-SiC by Traveling Solvent Method." Materials Science Forum 679-680 (March 2011): 36–39. http://dx.doi.org/10.4028/www.scientific.net/msf.679-680.36.

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We attempted the traveling solvent method (TSM) growth of SiC on 6H-SiC(0001) substrates using Si and Si-M (M=Ti, Cr and Dy) solvents at growth temperatures of 1500-1800°C. It was confirmed that 4H-SiC polytype was extremely stabilized in the highly carbon dissolved liquid phase. 4H-SiC growth on 6H-SiC, i.e. hetropolytype epitaxial growth, was observed only from Si-Dy solvent. The Dy content above 60at% was necessary to obtain 100% 4H-SiC polytype.

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Naik, Harsh, and T. Paul Chow. "Study of Mobility Limiting Mechanisms in (0001) 4H and 6H-SiC MOSFETs." Materials Science Forum 679-680 (March 2011): 595–98. http://dx.doi.org/10.4028/www.scientific.net/msf.679-680.595.

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To study the mobility limiting mechanisms in (0001) 4H-SiC and 6H-SiC MOSFETs, physics based modeling of the inversion mobility of has been done. Two very different limiting mechanisms have been found for 4H-SiC and 6H-SiC MOSFETs. The mobility in 6H-SiC MOSFETs is limited by phonon scattering while the 4H-SiC MOSFET mobility is limited by Coulombic at low electric fields and surface roughness scattering at high electric fields.

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Eto, Kazuma, Hiromasa Suo, Tomohisa Kato, and Hajime Okumura. "Growth of Low Resistivity p-Type 4H-SiC Crystals by Sublimation with Using Aluminum and Nitrogen Co-Doping." Materials Science Forum 858 (May 2016): 77–80. http://dx.doi.org/10.4028/www.scientific.net/msf.858.77.

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Low resistivity p-type SiC bulk crystals were grown by the sublimation method with using aluminum and nitrogen co-doping. In the sublimation growth of 4H-SiC, to obtain low-resistive p-type crystals are not easy because of the instability of 4H-SiC polytype with highly Al-doping. We have grown < 90 mΩcm p-type 4H-SiC bulk crystals with the co-doping condition. The results of SIMS and Raman spectroscopy show that high concentration of nitrogen co-doping could be effective to the stabilization of 4H polytype with p-type SiC growth.

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Glembocki, Orest J., Marek Skowronski, S. M. Prokes, D. Kurt Gaskill, and Joshua D. Caldwell. "Observation of Free Carrier Redistribution Resulting from Stacking Fault Formation in Annealed 4H-SiC." Materials Science Forum 527-529 (October 2006): 347–50. http://dx.doi.org/10.4028/www.scientific.net/msf.527-529.347.

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Bulk n+-4H-SiC wafers (n=1-2×1019 cm-3) containing annealing-induced stacking faults were examined by Raman scattering. The coupled plasmon-LO mode was observed to shift in a manner consistent with 1018 cm-3 doping in the 4H-SiC. Numerical simulations were performed using a self-consistent Poisson-Schrödinger solver and agree well with the experimental observations of carrier transfer from the 4H-SiC into the 3C-SiC stacking faults. The Raman data also shows that the 3C stacking faults induce a tensile strain on the surrounding 4H-SiC regions.

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Bai, Yun, Cheng Zhan Li, Hua Jun Shen, Yi Dan Tang, and Xin Yu Liu. "Structural Optimization of 4H-SiC BJT for Ultraviolet Detection with High Optical Gain." Materials Science Forum 858 (May 2016): 1036–39. http://dx.doi.org/10.4028/www.scientific.net/msf.858.1036.

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The 4H-SiC n-p-n BJT for ultraviolet detection with high optical gain is proposed and optimized in this paper. The effect of structural parameters of 4H-SiC phototransistor on the performance of the detectors is simulated and the effect mechanism is analyzed. The simulation results show that the 4H-SiC phototransistors detect UV light with a response wavelength below 380 nm. It is suggested that the base parameters are important to the responsivity of the 4H-SiC BJT. With optimized parameters the 4H-SiC UV phototransistor exhibits peak responsivity as high as 4617 A/W corresponding to a quantum gain of 2.2×105 under the bias voltage of 5 V.

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Yamamoto, Yuji, Kazuaki Seki, Shigeta Kozawa, Alexander, S. Harada, and Toru Ujihara. "Stable Growth of 4H-SiC Single Polytype by Controlling the Surface Morphology Using a Temperature Gradient in Solution Growth." Materials Science Forum 717-720 (May 2012): 53–56. http://dx.doi.org/10.4028/www.scientific.net/msf.717-720.53.

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We introduce a method to grow 4H-SiC single polytype stably by controlling the surface morphology. The polytype transition on on-axis 4H-SiC C-face was investigated from a viewpoint of surface morphology of grown layers. At the area where several hillock-like structures grew adjacently, the polytype transition from 4H-SiC to 6H-SiC or 15R-SiC often occurred. Therefore, we tried a modified seeded method to suppress the formation of hillock-like structures. As a result, the hillock-like structure on the grown layer was dramatically reduced. Moreover, the ratio of 4H-SiC polytype to the whole grown surface was increased to be almost 100%.

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Lim, Jang Kwon, Ludwig Östlund, Qin Wang, Wlodek Kaplan, Sergey A. Reshanov, Adolf Schöner, Mietek Bakowski, and Hans Peter Nee. "A Theoretical and Experimental Comparison of 4H- and 6H-SiC MSM UV Photodetectors." Materials Science Forum 717-720 (May 2012): 1207–10. http://dx.doi.org/10.4028/www.scientific.net/msf.717-720.1207.

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This paper reports on fabrication and modeling of 4H- and 6H-SiC metal-semiconductor-metal (MSM) photodetectors (PDs). MSM PDs have been fabricated on 4H-SiC and 6H-SiC epitaxial layers, and their performance analyzed by MEDICI simulation and measurements. The simulations were also used to optimize the sensitivity by varying the width and spacing of the interdigitated electrodes. The fabricated PDs with 2 µm wide metal electrodes and 3 µm spacing between the electrodes exhibited, under UV illumination, a peak current to dark current ratio of 105 and 104 in 4H-SiC and 6H-SiC, respectively. The measured spectral responsivity of 6H-SiC PDs was higher compared to that of 4H-SiC PDs, with a cutoff at 407 nm compared to 384 nm in 4H-SiC PDs. Also the peak responsivity occurred at a shorter wavelength in 6H material. A high rejection ratio between the photocurrent and dark current was found in both cases. These experimental results were in agreement with simulation.

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Seo, Han Seok, Ho Geun Song, Jeong Hyun Moon, Jeong Hyuk Yim, Myeong Sook Oh, Jong Ho Lee, Yu Jin Choi, and Hyeong Joon Kim. "Homoepitaxial Growth of 4H-SiC by Hot-Wall CVD Using BTMSM." Materials Science Forum 600-603 (September 2008): 151–54. http://dx.doi.org/10.4028/www.scientific.net/msf.600-603.151.

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Homoepitaxial growth of 4H-SiC epilayer by hot-wall chemical vapor deposition using bis-trimethylsilylmethane (BTMSM, C7H20Si2) precursor was investigated. The growth rate of 4H-SiC was investigated as a function of the growth temperature and source flow rate. The FWHM values of epilayers as the growth temperature and source flow rate also investigated. The growth rate of 4H-SiC epilayer grown by hot-wall CVD was 3.0 μm/h and the background doping level of 4H-SiC epilayer was mid 1015/cm3.

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Starke, Ulrich, W. Y. Lee, Camilla Coletti, Stephen E. Saddow, Robert P. Devaty, and Wolfgang J. Choyke. "SiC Pore Surfaces: Surface Studies of 4H-SiC(1-102) and 4H-SiC(-110-2)." Materials Science Forum 527-529 (October 2006): 677–80. http://dx.doi.org/10.4028/www.scientific.net/msf.527-529.677.

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The morphology and atomic structure of 4H-SiC(1102) and 4H-SiC(1102) surfaces, i.e. the surfaces found in the triangular channels of porous 4H-SiC, have been investigated using AFM, LEED and AES. After hydrogen etching the surfaces show steps parallel and perpendicular to the caxis, yet drastically different morphologies for the two isomorphic orientations. Both surfaces immediately display a sharp LEED pattern. Together with the presence of oxygen in the AES spectra this indicates the development of an ordered oxide. Both surfaces show an oxygen free, well ordered surface after Si deposition and annealing.

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Ryu, Sei Hyung, Sumi Krishnaswami, Mrinal K. Das, Jim Richmond, Anant K. Agarwal, John W. Palmour, and James D. Scofield. "4H-SiC DMOSFETs for High Speed Switching Applications." Materials Science Forum 483-485 (May 2005): 797–800. http://dx.doi.org/10.4028/www.scientific.net/msf.483-485.797.

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Due to the high critical field in 4H-SiC, the drain charge and switching loss densities in a SiC power device are approximately 10X higher than that of a silicon device. However, for the same voltage and resistance ratings, the device area is much smaller for the 4H-SiC device. Therefore, the total drain charge and switching losses are much lower for the 4H-SiC power device. A 2.3 kV, 13.5 mW-cm2 4H-SiC power DMOSFET with a device area of 2.1 mm x 2.1 mm has been demonstrated. The device showed a stable avalanche at a drain bias of 2.3 kV, and an on-current of 5 A with a VGS of 20 V and a VDS of 2.6 V. Approximately an order of magnitude lower parasitic capacitance values, as compared to those of commercially available silicon power MOSFETs, were measured for the 4H-SiC power DMOSFET. This suggests that the 4H-SiC DMOSFET can provide an order of magnitude improvement in switching performance in high speed switching applications.

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Ettisserry, D. P., Neil Goldsman, Akin Akturk, and Aivars J. Lelis. "Mechanisms of Nitrogen Incorporation at 4H-SiC/SiO₂ Interface during Nitric Oxide Passivation – A First Principles Study." Materials Science Forum 858 (May 2016): 465–68. http://dx.doi.org/10.4028/www.scientific.net/msf.858.465.

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In this work, we investigate the behavior of Nitrogen atoms at 4H-Silicon Carbide (4H-SiC)/Silicon dioxide (SiO2) interface during nitric oxide passivation using ab-initio Density Functional Theory. Our calculations suggest different possible energetically favorable and competing mechanisms by which nitrogen atoms could a) incorporate themselves into the oxide, just above the 4H-SiC substrate, and b) substitute for carbon atoms at the 4H-SiC surface. We attribute the former process to cause increased threshold voltage instability (hole traps), and the latter to result in improved effective mobility through channel counter-doping, apart from removing interface traps in 4H-SiC power MOSFETs. These results support recent electrical and XPS measurements. Additionally, Nitric Oxide passivation is shown to energetically favor re-oxidation of the 4H-SiC surface accompanied by the generation of oxygen vacancies under the conditions considered in this work.

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Noborio, Masato, Jun Suda, and Tsunenobu Kimoto. "High Channel Mobility in P-Channel MOSFETs Fabricated on 4H-SiC (0001) and Non-Basal Faces." Materials Science Forum 615-617 (March 2009): 789–92. http://dx.doi.org/10.4028/www.scientific.net/msf.615-617.789.

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P-channel MOSFETs have been fabricated on 4H-SiC (0001) face as well as on 4H-SiC (03-38) and (11-20) faces. The gate oxides were formed by thermal oxidation in dry N2O ambient, which is widely accepted to improve the performance of n-channel SiC MOSFETs. The p-channel SiC MOSFETs with N2O-grown oxides on 4H-SiC (0001), (03-38), and (11-20) faces show a channel mobility of 7 cm2/Vs, 11 cm2/Vs, and 17 cm2/Vs, respectively. From the quasi-static C-V curves measured by using gate-controlled diodes, the interface state density was calculated by an original method. The interface state density was the lowest at the SiO2/4H-SiC (03-38) interface (about 1x1012 cm-2eV-1 at EV + 0.2 eV). The authors have applied deposited oxides to the 4H-SiC p-channel MOSFETs. The (0001), (03-38), and (11-20) MOSFETs with deposited oxides exhibit a channel mobility of 10 cm2/Vs, 13 cm2/Vs, and 17 cm2/Vs, respectively. The deposited oxides are one of effective approaches to improve both n-channel and p-channel 4H-SiC MOS devices.

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Li, Liang, Lei, Hong, Li, Li, Ghaffar, Li, and Xiong. "Quantitative Analysis of Piezoresistive Characteristic Based on a P-type 4H-SiC Epitaxial Layer." Micromachines 10, no. 10 (September 20, 2019): 629. http://dx.doi.org/10.3390/mi10100629.

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In this work, the piezoresistive properties of heavily doped p-type 4H-SiC at room temperature were investigated innovatively. It was verified by a field emission scanning electron microscope (FESEM), X-ray diffraction (XRD), and laser Raman spectroscopy (LRS) that the crystal quality of the epitaxial layer was good. The doping concentration and thickness of the epitaxial layer were measured by secondary ion mass spectrometry (SIMS) to be ~1.12 × 1019 cm−3 and ~1.1 μm, respectively. The 4H-SiC cantilever beam along crystal orientation was fabricated, and the fixed end of the cantilever beam was integrated with longitudinal and transverse p-type 4H-SiC piezoresistors. A good ohmic contact was formed between Ni/Ti/Al/Au and a p-type 4H-SiC piezoresistor under nitrogen environment annealing at 1050 °C for 5 min. The free end of the cantilever beam was forced to cause strain on the p-type 4H-SiC piezoresistor, and then the resistances were measured by a high precision multimeter. The experimental results illustrated that longitudinal and transverse gauge factors (GFs) of the p-type 4H-SiC piezoresistors were 26.7 and −21.5, respectively, within the strain range of 0–336με. In order to further verify the electro-mechanical coupling effect of p-type 4H-SiC, the piezoresistors on the beam were connected to the Wheatstone full-bridge circuit and the output changes were observed under cyclic loading of 0–0.5 N. The measuring results revealed that the transducer based on the 4H-SiC piezoresistive effect exhibited good linearity and hysteresis, which confirmed that p-type 4H-SiC has the potential for pressure or acceleration sensing applications.

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Huang, Yuanchao, Rong Wang, Naifu Zhang, Yiqiang Zhang, Deren Yang, and Xiaodong Pi. "Effect of hydrogen on the unintentional doping of 4H silicon carbide." Journal of Applied Physics 132, no. 15 (October 21, 2022): 155704. http://dx.doi.org/10.1063/5.0108726.

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High-purity semi-insulating (HPSI) 4H silicon carbide (4H-SiC) single crystals are critical semiconductor materials for fabricating GaN-based high-frequency devices. One of the major challenges for the growth of HPSI 4H-SiC single crystals is the unintentional doping of nitrogen (N) and boron (B). The addition of hydrogen has been supposed to mitigate unintentional doping. However, the underlying mechanism has not been well understood. In this work, the role of hydrogen in the growth of HPSI 4H-SiC single crystals is investigated by first-principles formation-energy calculations. We find that the addition of hydrogen significantly mitigates N doping while hardly affecting B doping. Once hydrogen is added, hydrogen may adsorb at the growing surface of 4H-SiC, leading to surface passivation. Since N can react with hydrogen to form stable NH3 (g), the chemical potential of N is reduced, so that the formation energy of N in 4H-SiC increases. Hence, the critical partial pressure of nitrogen required for the growth of HPSI 4H-SiC single crystals increases by two orders of magnitude. Moreover, we reveal that the adjustment of relative B and N doping concentrations has a substantial impact on the Fermi energy of HPSI 4H-SiC. When the doping concentration of N is higher than that of B, N interacts with carbon vacancies (VC) to pin the Fermi energy at Z1/2. When the doping concentration of B is higher than that of N, the Fermi energy is pinned at EH6/7. This explains that the resistivity of unintentionally doped HPSI 4H-SiC may vary.

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Tsuchida, Hidekazu, Isaho Kamata, Masahiko Ito, Tetsuya Miyazawa, Norihiro Hoshino, Hiroaki Fujibayashi, Hideki Ito, et al. "Evolution of Fast 4H-SiC CVD Growth and Defect Reduction Techniques." Materials Science Forum 778-780 (February 2014): 85–90. http://dx.doi.org/10.4028/www.scientific.net/msf.778-780.85.

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This paper introduces our recent challenges in fast 4H-SiC CVD growth and defect reduction. Enhanced growth rates in 4H-SiC epitaxial growth by high-speed wafer rotation and in a high-temperature gas source method promoting SiC bulk growth by increasing the gas flow velocity are demonstrated. Trials and results of deflecting threading dislocations by patterned C-face 4H-SiC epitaxial growth are also shown.

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Huang, Yuanchao, Yixiao Qian, Yiqiang Zhang, Deren Yang, and Xiaodong Pi. "Kick-out diffusion of Al in 4H-SiC: an ab initio study." Journal of Applied Physics 132, no. 1 (July 7, 2022): 015701. http://dx.doi.org/10.1063/5.0096577.

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As a semiconductor with a wide bandgap, 4H silicon carbide (4H-SiC) has considerable potential for high-temperature and high-power devices. It is widely established that p-type 4H-SiC is formed predominantly by doping Al. Although Al diffusion in 4H-SiC is often negligible at low temperatures due to the tight bonding of Al in 4H-SiC, the diffusion coefficient of Al dramatically rises when the temperature is rather high. While diffusion is the most fundamental physical processes, the diffusion mechanism of Al in 4H-SiC remains unknown. Due to the large atomic radius of Al relative to the host Si/C atoms and the fact that Al occupies the Si lattice in 4H-SiC, the diffusion of Al is typically mediated by point defects such as vacancies and self-interstitials. We now investigate the diffusion of Al in 4H-SiC using first-principles calculations and compare the activation energy of Al diffusion mediated by carbon vacancies (VC) to that of Al diffusion mediated by Si interstitials (Sii). It is found that Al diffusion is actually a Sii-mediated process, in which a nearby Sii first kicks a substitutional Al atom to an interstitial site. The kicked-out Al then spreads via interstitial sites. The diffusion coefficient is calculated, which is comparable to experimental results.

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Sonde, Sushant, Carmelo Vecchio, Filippo Giannazzo, Rositza Yakimova, Emanuele Rimini, and Vito Raineri. "Local Electrical Properties of the 4H-SiC(0001)/Graphene Interface." Materials Science Forum 679-680 (March 2011): 769–76. http://dx.doi.org/10.4028/www.scientific.net/msf.679-680.769.

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Local current transport across graphene/4H-SiC was studied with nanometric scale lateral resolution by Scanning Current Spectroscopy on both graphene grown epitaxially on 4H-SiC(0001) (EG-SiC) and graphene exfoliated from highly oriented pyrolitic graphite and deposited on 4H-SiC(0001) (DG-SiC). The study revealed that the Schottky barrier height (SBH) of EG/4H-SiC(0001) is lowered by ~0.49eV. This is explained in terms of Fermi-level pinning above the Dirac point in EG due to the presence of positively charged states at the interface between Si face of 4H-SiC and carbon-rich buffer layer. Furthermore, Scanning Capacitance Spectroscopy based method allowed evaluating local electron mean free path (lgr) in graphene. lgr in EG-SiC was observed to be, on average, ~0.4 times that in DG-SiC and exhibited large point-to-point variations due to presence of laterally homogeneous positively charged buffer layer at the interface. However, lgr in graphene on SiC was observed to be larger than on standard SiO2 samples (DG-SiO2), which is explained by better dielectric screening of charged impurities and lower surface polar phonon scattering at the graphene/substrate interface.

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Lebedev, A. A., G. A. Oganesyan, V. V. Kozlovski, I. A. Eliseyev, and P. V. Bulat. "Radiation Defects in Heterostructures 3C-SiC/4H-SiC." Crystals 9, no. 2 (February 22, 2019): 115. http://dx.doi.org/10.3390/cryst9020115.

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The effect of 8 MeV proton irradiation on n-3C-SiC epitaxial layers grown by sublimation on semi-insulating 4H-SiC substrates has been studied. Changes in sample parameters were recorded using the Hall-effect method and judged from photoluminescence spectra. It was found that the carrier removal rate (Vd) in 3C-SiC is ~100 cm−1, which is close to Vd in 4H-SiC. Compared with 4H and 6H silicon carbide, no significant increase in the intensity of the so-called defect-related photoluminescence was observed. An assumption is made that radiation-induced compensation processes in 3C-SiC are affected by structural defects (twin boundaries), which are always present in epitaxial cubic silicon carbide layers grown on substrates of the hexagonal polytypes.

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Wilson, S., C. S. Dickens, J. Griffin, and M. G. Spencer. "Comparative Growth of AlN on Singular and Off-Axis 6H and 4H-SiC by MOCVD." MRS Internet Journal of Nitride Semiconductor Research 4, S1 (1999): 344–50. http://dx.doi.org/10.1557/s1092578300002702.

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A comparison study of the growth of aluminum nitride (AlN) single crystal epitaxy on 6H-SiC and 4H-SiC substrates has been performed. The material has been characterized using atomic force microscopy (AFM) and reflective high energy electron diffraction (RHEED). AlN crystals were deposited on the following 6H-SiC substrates: singular with and without an initial SiC epilayer, and 3.5° off-axis with and without an initial SiC epilayer. AlN crystals were deposited on 8.0° off-axis 4H-SiC with and without initial SiC epilayers. AFM shows that the deposition of AlN on 6H-SiC and 4H-SiC with an initial SiC epilayer displays high quality quasi-two dimensional growth as atomically flat or step flow epitaxy.

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Okamoto, Dai, Hiroshi Yano, Tomoaki Hatayama, Yukiharu Uraoka, and Takashi Fuyuki. "Criteria for Accurate Measurement of Charge-Pumping Current in 4H-SiC MOSFETs." Materials Science Forum 600-603 (September 2008): 747–50. http://dx.doi.org/10.4028/www.scientific.net/msf.600-603.747.

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This paper describes the influence of the geometric component in the charge-pumping measurement of 4H-SiC MOSFETs. Charge-pumping measurements were conducted on 4H-SiC MOSFETs with and without NO annealing. Charge-pumping measurements with different pulse-fall times revealed that the geometric component exists in 4H-SiC MOSFETs and is especially large in the unannealed MOSFETs. A sufficiently long fall-time is needed to minimize its effect, which is expected to be 1–10 μs for 4H-SiC MOSFETs with a gate length of 10 μm.

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Hiyoshi, Toru, Takeyoshi Masuda, Keiji Wada, Shin Harada, and Yasuo Namikawa. "Improvement of Interface State and Channel Mobility Using 4H-SiC (0-33-8) Face." Materials Science Forum 740-742 (January 2013): 506–9. http://dx.doi.org/10.4028/www.scientific.net/msf.740-742.506.

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In this paper, we characterized MOS devices fabricated on 4H-SiC (0-33-8) face. The interface state density of SiO2/4H-SiC(0-33-8) was significantly low compared to that of SiO2/4H-SiC(0001). The field-effect channel mobility obtained from lateral MOSFET (LMOSFET) was 80 cm2/Vs, in spite of a high p-well concentration of 5x1017 cm-3 (implantation). The double implanted MOSFET (DMOSFET) fabricated on 4H-SiC(0-33-8) showed a specific on-resistance of 4.0 mΩcm2 with a blocking voltage of 890 V.

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Park, Jong Hwi, Tae Kyoung Yang, Il Soo Kim, Won Jae Lee, Im Gyu Yeo, Tai Hee Eun, Seung Suk Lee, Jang Yul Kim, and Myoung Chul Chun. "Process and Crucible Modification for Growth of High Doped 4H-SiC Crystal with Larger Diameter." Materials Science Forum 717-720 (May 2012): 17–20. http://dx.doi.org/10.4028/www.scientific.net/msf.717-720.17.

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The present research was focused to investigate various process parameters influenced on the large 4H-SiC crystal growth on a 6H-SiC seed by PVT method. The crucible diameter along horizontal axial direction and inserted graphite ring was modified to change the growth parameter like the temperature gradient. In the initial stage of growth, foreign polytypes such as 6H/4H were observed on 6H-SiC seed, indicating the growth temperature to be unstable on crystal surface. However, from the middle of growth step, 4H-SiC was successfully formed in the ingot with the modification of growth pressure and a SIMS analysis confirmed the high doping concentration in grown 4H-SiC crystal.

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Aoki, Masahiko, Megumi Miyazaki, Taro Nishiguchi, Hiroyuki Kinoshita, and Masahiro Yoshimoto. "TEM Observation of the Polytype Transformation of Bulk SiC Ingot." Materials Science Forum 600-603 (September 2008): 365–68. http://dx.doi.org/10.4028/www.scientific.net/msf.600-603.365.

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This article describes the analysis of the polytype transformation of SiC ingot. We analyzed the sample by Raman spectroscopy and TEM observation. The result of the analysis shows the polytype is transformed from 4H-SiC to 6H-SiC, and then returned to 4H-SiC. We found that the direction of the c-axis is not the same as the growth direction of the ingot. And also we found the existence of 8H-SiC at the interface between 6H-SiC and 4H-SiC region by the selected area diffraction pattern and confirmed it by HR-TEM observation.

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Geng, Wenhao, Guang Yang, Xuqing Zhang, Xi Zhang, Yazhe Wang, Lihui Song, Penglei Chen, et al. "Identification of subsurface damage of 4H-SiC wafers by combining photo-chemical etching and molten-alkali etching." Journal of Semiconductors 43, no. 10 (October 1, 2022): 102801. http://dx.doi.org/10.1088/1674-4926/43/10/102801.

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Abstract In this work, we propose to reveal the subsurface damage (SSD) of 4H-SiC wafers by photo-chemical etching and identify the nature of SSD by molten-alkali etching. Under UV illumination, SSD acts as a photoluminescence-black defect. The selective photo-chemical etching reveals SSD as the ridge-like defect. It is found that the ridge-like SSD is still crystalline 4H-SiC with lattice distortion. The molten-KOH etching of the 4H-SiC wafer with ridge-like SSD transforms the ridge-like SSD into groove lines, which are typical features of scratches. This means that the underlying scratches under mechanical stress give rise to the formation of SSD in 4H-SiC wafers. SSD is incorporated into 4H-SiC wafers during the lapping, rather than the chemical mechanical polishing (CMP).

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Kildemo, Morten, Ulrike Grossner, Bengt Gunnar Svensson, and S. Raaen. "XPS Study of the Electronic Properties of the Ce/4H-SiC Interface, and the Formation of the SiO₂/Ce₂Si₂O₇/4H-SiC Interface Structure upon Oxidation." Materials Science Forum 556-557 (September 2007): 549–54. http://dx.doi.org/10.4028/www.scientific.net/msf.556-557.549.

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The deposition and annealing in ultra high vacuum (UHV) of 5-6 monolayers (ML) of cerium on clean reconstructed Si-face 4H-SiC (0001) is studied by x-ray photoemission spectroscopy (XPS). Band bending as a function of annealing was studied by shifts of the bulk peak contribution in the C1s and Si2p spectra relative to the clean reconstructed surface. Additional datapoints for Schottky barrier formation on 4H-SiC are thus obtained by the low work function rareearth metals, and presented in the framework of the metal-induced-gap states and electronegativity model. A Ce/CeSi2-x/4H-SiC interface alloy forms by annealing to 850-1050oC. Kinetic information from the oxidation of the Ce/CeSi2-x/4H-SiC interface alloy is also reported. In particular, a SiO2- x/Ce-Si mixed oxide/4H-SiC forms upon oxidation. The shift of the C1s SiC-bulk-peak towards higher binding energies upon oxidation indicates that the mixed Ce-Si oxide interface layer appears to passivate the near Fermi-level 4H-SiC interface states at least as well as SiO2, and are expected to modify the electrical interface characteristics.

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Huang, Yuanchao, Rong Wang, Yiqiang Zhang, Deren Yang, and Xiaodong Pi. "Compensation of p-type doping in Al-doped 4H-SiC." Journal of Applied Physics 131, no. 18 (May 14, 2022): 185703. http://dx.doi.org/10.1063/5.0085510.

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One of the major challenges of 4H-silicon carbide (4H-SiC) is that the preparation of low resistivity p-type 4H-SiC single crystals lags seriously behind that of low resistivity n-type 4H-SiC single crystals, hindering the development of important 4H-SiC power devices such as n-channel insulated gate bipolar transistors. In particular, the resistivity of p-type 4H-SiC single crystals prepared through the physical vapor transport technique can only be lowered to around 100 mΩ cm. One of the key causes is the incomplete ionization of the p-type dopant Al with an ionization energy ∼0.23 eV. Another factor is the compensating effect. It cannot simply assume nitrogen (N) is the sole compensatory center, since the number of the compensating center is larger than the concentration of N doping. In this work, we systematically investigate the compensation of native defects and self-compensation in Al-doped 4H-SiC. It is found that the positively charged carbon vacancies [Formula: see text] are also the dominant compensating centers in Al-doped 4H-SiC. When the Al concentration is in the range of 1016–1019 cm−3, the concentration of holes is lower by one order of magnitude than the Al concentration because of the compensation of [Formula: see text]. As the Al concentration exceeds 1020 cm−3, the concentration of holes is only in the order of magnitude of 1019 cm−3 owing to the dominant compensation of [Formula: see text] and supplementary self-compensation of interstitial Al [Formula: see text]. We propose that the passivation of [Formula: see text] as well as quenching is effective to enhance the hole concentration of Al-doped 4H-SiC.

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Ushio, Shoji, Tatsuya Karaki, Kenta Hagiwara, Noboru Ohtani, and Tadaaki Kaneko. "Surface Phase Diagram of 4H-SiC {0001} Step-Terrace Structures during Si-Vapor Etching in a TaC Crucible." Materials Science Forum 717-720 (May 2012): 573–76. http://dx.doi.org/10.4028/www.scientific.net/msf.717-720.573.

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Step-terrace structures were observed at on-axis/4o off 4H-SiC {0001} surfaces after Si-vapor etching which we have been supposed as an original technique to planarize and etch the SiC surfaces by utilizing a TaC crucible in temperature ranged from 1600 to 2200 oC. The structures obtained after the Si-vapor etching obviously indicated temperature dependence. There were two types of step-terrace structures in terms of the step height and the shape of the step edges at on-axis surfaces. Step bunched surfaces consisting of full unit cell height (= 1.0 nm) steps with {1-10n} facets at the step edges were observed at 4H-SiC (0001) in lower temperatures below 2000 oC, while smooth isotropic surfaces with half unit cell height (= 0.5 nm) steps and without any stable facets at the step edges were observed at 4H-SiC (0001) in higher temperatures above 2000 oC and in all temperature conditions (1600 - 2200 oC) at 4H-SiC (000-1). Similar tendency was also confirmed at 4o off 4H-SiC {0001} surfaces. From the comparison with 6H-SiC, macro step bunching (~10 nm height) was revealed to be a unique phenomenon at 4H-SiC (0001) surface in the etching.

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Yeo, Im Gyu, Tae Woo Lee, Jong Hwi Park, Woo Sung Yang, Heui Bum Ryu, Mi Seon Park, Il Soo Kim, et al. "The Effect of Process Parameters on 4H-SiC Single Crystal Grown by a PVT Method." Materials Science Forum 679-680 (March 2011): 40–43. http://dx.doi.org/10.4028/www.scientific.net/msf.679-680.40.

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Extensive study of various process parameters to influence on the growth of 4H-SiC crystal has been carried out using the transformation of the 6H-SiC seed by a PVT method. The axial temperature gradients were increased throughout increasing the crucible length along growth direction in order to enhance the growth rate and transformed crystal yield. The N2/Ar gas ratio used during the crystal growth related with carrier concentration/mobility of grown crystal. In the initial stage of growth, foreign polytypes such as 6H/15R were observed on 6H-SiC seed crystal but 4H crystals were entirely grown after the process optimization. While the typical absorption spectrum of SiC seed crystal indicated that the SiC polytype was the 6H-SiC with fundamental absorption energy of about 3.02eV, absorption spectrum of grown SiC crystal exhibited 4H-SiC with fundamental absorption energy of about 3.26eV. The entirely transformed SiC region exhibited lower micropipe density than 6H/4H transition region.

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Cuong, Vuong Van, Seiji Ishikawa, Hiroshi Sezaki, Tomonori Maeda, Satoshi Yasuno, Tomoyuki Koganezawa, and Shinichiro Kuroki. "Optimization of Ni/Nb Ratio for High-Temperature-Reliable Ni/Nb Silicide Ohmic Contact on 4H-SiC." Materials Science Forum 963 (July 2019): 498–501. http://dx.doi.org/10.4028/www.scientific.net/msf.963.498.

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Low specific contact resistivity and high-temperature reliability of the Ni (x)/Nb (100-x) (where x = 25, 50, 75 nm) ohmic contact to 4H-SiC were investigated. After the annealing process at 1000°C for 3 min in N2 ambient, the I-V curves indicated that all the contacts exhibited the ohmic behaviors. Based on the transfer length method, the specific contact resistivity of the contacts were extracted. High concentration of Ni was responsible for low specific contact resistance of the Ni (75)/Nb (25)/4H-SiC sample by the formation of Ni2Si compound after the fabrication process. However, this contact lost the ohmic behavior at low temperature of 150°C. Whereas, both Ni (50)/Nb (50)/4H-SiC and Ni (25)/Nb (75)/4H-SiC contacts remained the ohmic behavior for 100-hour aging at 400°C. Two-dimensional X-ray diffraction analyses showed that the presence of carbon agglomeration formed at the interface of the Ni (75)/Nb (25)/4H-SiC contact caused the degradation of this sample when being aged at high temperature environment. Meanwhile, higher concentration of Nb in the Ni (50)/Nb (50)/4H-SiC and Ni (25)/Nb (75)/4H-SiC samples improved the ability to collect the excess carbon atoms and thus enhanced the high temperature reliability of these contacts when operating in high temperature ambient. Considering both low specific contact resistivity and high temperature reliability, the Ni (50)/Nb (50)/4H-SiC contact can be a good candidate for harsh environment applications.

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ul Hassan, Jawad, Patrik Ščajev, Kęstutis Jarašiūnas, and Peder Bergman. "Optically Detected Temperature Dependences of Carrier Lifetime and Diffusion Coefficient in 4H- and 3C-SiC." Materials Science Forum 679-680 (March 2011): 205–8. http://dx.doi.org/10.4028/www.scientific.net/msf.679-680.205.

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Free carrier dynamics has been studied in 4H- and 3C-SiC in a wide temperature range using time-resolved photoluminescence, free carrier absorption, and light induced transient grating techniques. Considerably high carrier lifetime was observed in 3C-SiC epitaxial layers grown on 4H-SiC substrates using hot-wall CVD with respect to previously reported values for 3C-SiC grown either on Si or on 6H-SiC substrates. The temperature dependences of carrier lifetime and diffusion coefficient for 4H- and 3C-SiC were compared. Shorter photoluminescence decay time with respect to free carrier absorption decay time was observed in the same 4H-SiC sample, while these techniques revealed similar trends in the carrier lifetime temperature dependencies. However, the latter dependences for hot-wall CVD-grown 3C layers were found different if measured by time resolved photoluminescence and free carrier absorption techniques.

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Berger, Clement, Jean François Michaud, David Chouteau, and Daniel Alquier. "Laser Annealing Simulations of Metallisations Deposited on 4H-SiC." Materials Science Forum 963 (July 2019): 502–5. http://dx.doi.org/10.4028/www.scientific.net/msf.963.502.

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Based on finite elements method, thermal simulations were conducted to reproduce a laser annealing of several common metals deposited on 4H-SiC. We estimated the temperature reached at the metal/4H-SiC interface to check the possibility to achieve ohmic contact formation through laser annealing. An optimization of Al/Ti/4H-SiC stacking was also considered. Simulations highlighted the low temperature of the non-irradiated SiC face that allows using grinded wafer.

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Afanasev A. V., Ilyin V. A., Luchinin V. V., Serkov A. V., and Chigirev D. A. "On the Formation of Low-Resistivity Contacts for 4H-SiC Bipolar Devices." Semiconductors 56, no. 6 (2022): 442. http://dx.doi.org/10.21883/sc.2022.06.53548.9827.

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The results of studies on the development of technological methods for the formation of low-resistivity contact systems to n- and p-SiC based on single and multilayer Ni-, Al- and Ti-compositions for 4H-SiC based bipolar devices are presented. It is shown that the formation of low-resistivity contacts based on Ni to n-4H-SiC (rhoc=3.6·10-4 Ohm·cm2) and Ni/Al to p-4H-SiC (rhoc=5.9·10-5 Ohm·cm2) is possible within a single cycle of vacuum annealing at 1000oC for 120 s. This technological solution makes it possible to reduce the number of high-temperature processes. Keywords: 4H-SiC, n-type, p-type, ohmic contacts, RTA, TLM, specific contact resistivity.

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Shen, Zhan Wei, Feng Zhang, Sima Dimitrijev, Ji Sheng Han, Li Xin Tian, Guo Guo Yan, Zheng Xin Wen, et al. "Prediction of High-Density and High-Mobility Two-Dimensional Electron Gas at Al_xGa_1-xN/4H-SiC Interface." Materials Science Forum 897 (May 2017): 719–22. http://dx.doi.org/10.4028/www.scientific.net/msf.897.719.

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This work presents theoretical demonstration of two-dimensional electron gas (2DEG) at the interface between Al0.2Ga0.8N and 4H-SiC, based on the self-consistent solution of Schrödinger–Poisson equations. High sheet carrier density of 1.1×1013 cm-2 was obtained in the Al0.2Ga0.8N/4H-SiC heterostructure, which is comparable to the electron concentration in Al0.2Ga0.8N/GaN heterostructure. The current–voltage characteristics of a high-electron-mobility transistor (HEMT), based on the Al0.2Ga0.8N/4H-SiC heterostructure, show a saturated drain current of 1.5 A/mm at the gate voltage of 2 V and the transconductance of 194 mS/mm at -3.95 V. In spite of interface-roughness scattering and phonon scattering, the 2DEG at the AlxGa1-xN/4H-SiC interface exhibits high electron mobility values of 3365 cm2/ (V·s) at 77K and 1120 cm2/ (V·s) at 300K. These results indicate that AlxGa1-xN/4H-SiC heterostructure can significantly improve the mobility of SiC based power switching devices.

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Fiorenza, Patrick, Filippo Giannazzo, Lukas K. Swanson, Alessia Frazzetto, Simona Lorenti, Mario S. Alessandrino, and Fabrizio Roccaforte. "A look underneath the SiO2/4H-SiC interface after N2O thermal treatments." Beilstein Journal of Nanotechnology 4 (April 8, 2013): 249–54. http://dx.doi.org/10.3762/bjnano.4.26.

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The electrical compensation effect of the nitrogen incorporation at the SiO2/4H-SiC (p-type) interface after thermal treatments in ambient N2O is investigated employing both scanning spreading resistance microscopy (SSRM) and scanning capacitance microscopy (SCM). SSRM measurements on p-type 4H-SiC areas selectively exposed to N2O at 1150 °C showed an increased resistance compared to the unexposed ones; this indicates the incorporation of electrically active nitrogen-related donors, which compensate the p-type doping in the SiC surface region. Cross-sectional SCM measurements on SiO2/4H-SiC metal/oxide/semiconductor (MOS) devices highlighted different active carrier concentration profiles in the first 10 nm underneath the insulator–substrate interface depending on the SiO2/4H-SiC roughness. The electrically active incorporated nitrogen produces both a compensation of the acceptors in the substrate and a reduction of the interface state density (D it). This result can be correlated with the 4H-SiC surface configuration. In particular, lower D it values were obtained for a SiO2/SiC interface on faceted SiC than on planar SiC. These effects were explained in terms of the different surface configuration in faceted SiC that enables the simultaneous exposition at the interface of atomic planes with different orientations.

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Journal articles on the topic '4H-SiC'

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