Academic literature on the topic 'InGaAs Linear Detector Arrays'

In this work, we fabricated dual-band 800 × 2 short-wave infrared (SWIR) indium gallium arsenide (InGaAs) focal-plane arrays (FPAs) using N-InP/i-In0.53Ga0.47As/N-InP double-heterostructure materials, which are often applied in ocean-color remote sensing. Using narrow-band interference-filter integration, our detector-adopted planner structure produced two detection channels with center wavelengths of 1.24 and 1.64 μm, and a full-width half-maximum (FWHM) of 0.02 μm for both channels. The photoelectric characteristics of the spectral response, modulation transfer function (MTF), and detectability of the detector were further analyzed. Our FPAs showed good MTF uniformity with pixel operability as high as 100% for each 800 × 1 linear array. Peak detectivity reached 4.39 × 1012 and 5.82 × 1012 cm·Hz1/2/W at 278 K, respectively, and response nonuniformity was ideal at 2.48% and 2.61%, respectively. As a final step, dual-band infrared detection imaging was successfully carried out in push-broom mode.

Due to the development of cost-efficient detector technologies in the NIR (Near Infrared), new areas of application are constantly being addressed. This affects autonomous driving, where LiDAR (Light Detection and Ranging) systems with better eye safety are being developed, as well as low-cost night vision cameras. Another area of application is NIR spectroscopy, e.g. in the areas of food monitoring, environmental research or medical technology. The increasing need for portable, low-cost analysis devices, for example for "on-site" measurements or for everyday life, is driving the development of highly miniaturized and low-cost lab-on-a-chip systems. The NIR detectors and NIR cameras available on the market are primarily based on materials from group III/V compound semiconductors, e.g. InGaAs. However, the CMOS (Complementary Metal Oxide Semiconductor) standard process cannot be used for the production of this technology, which significantly increases the cost factor and thus limits its use on the market. A promising alternative is offered by group IV based detectors, in particular Ge and GeSn detectors, which can be monolithically integrated on a Si substrate. As a result, such detector systems can be processed much more cost-efficiently with CMOS compatible standard technology. The NIR absorption properties are also comparable to III/V components. This paper reports on the monolithic integration of Ge and GeSn detector arrays on Si substrates for the realization of a camera system. The entire system consists of a photonic chip, a readout chip and a standard microcontroller, which is connected to a laptop via USB. The SNR (signal-to-noise ratio) is an important parameter for such an integrated system. The quantum efficiency of each individual pixel sensor has to be maximized and a high fill factor per pixel is aimed for. A particularly high fill factor is achieved here with optical light coupling via the substrate back-side, since the front-side metallization does not interfere with the optical coupling area. Furthermore, the metallization acts then as a mirror, the light thus passes through the absorption area twice and leads to a higher quantum efficiency. However, the main obstacle of Ge and GeSn, compared to III/V devices, is the higher intrinsic charge carrier concentration, which leads to a significantly higher dark current. A possible solution is the zero bias operation of the detector at the expected dark current minimum. The dark current is 3 orders of magnitude smaller at 0 V compared to an operating point at -1 V. Another criterion for the circuit is that a signal range or photocurrent supports a wide dynamic range (between nA and µA). For this purpose, the photocurrent is fed into the evaluation electronics via a triple cascaded current mirror. The measured value is output to a 12-bit ADC (Analog Digital Converter) integrated in the microcontroller via a current/voltage converter, two buffers and a sample hold element. With the help of additional multiplexers, the circuit can be used to read out several detectors and thus address a pixel matrix. We report on the fabrication of the photonic chip, which is carried out using CMOS compatible processes and MEMS (Micro-Electro-Mechanical System) processes in combination with an epitaxial growth of the active device structures. The photonic chip is based on 150 mm Si substrates, which were prepared first with multiple ion implantation steps. The active pin detector layers, consisting of Si and Ge or GeSn, were grown by means of molecular beam epitaxy. Afterwards, deep trenches were now etched between the detectors in a MEMS process to minimize crosstalk between neighboring pixels. The detectors were structured then using CMOS processes, and the backside is polished or structured. Finally, a two layer frontside-metallization is applied for the contacts. We demonstrate the functionality of both two-dimensional and linear detector arrays and show possible applications such as NIR cameras or NIR spectrometers.

Quantum well infrared photodetectors (QWIPs) have been widely investigated for the 3–5 μm mid-wavelength infrared (MWIR) and 8–12 μm long-wavelength infrared (LWIR) atmospheric spectral windows as well as very long wavelength infrared (VLWIR: λc > 14 μm) imaging array applications in the past decade. The mature III-V compound semiconductor growth technology and the design flexibility of device structures have led to the rapid development of various QWIP structures for infrared focal plane arrays (FPAs) applications. In addition to the single-color QWIP with narrow bandwidth, multi-color or broadband QWIPs required for advanced IR sensing and imaging applications have also emerged in recent years. Using band gap engineering approach, the multi-color (2, 3, and 4-color) QWIPs with multi-stack quantum wells and voltage-tunable asymmetrical coupled quantum well structures for detection in the MWIR, LWIR, and VLWIR bands have been demonstrated recently. The triple-coupled (TC-) QWIP employs the quantum confined Stark effect to tune the peak detection wavelength by the applied bias voltage, A typical single-color QWIP exhibits a rather narrow spectral bandwidth of 1 to 2 μm. For certain applications, such as spectroscopy, sensing of a broader range of infrared radiation is highly desirable. Using the stacked quantum wells with different well width and depth, the digital-graded superlattice barrier (DGSLB) or the linear-graded barrier (LGB) structures, broadband (BB-) QWIPs covering the 8–14 μm atmospheric spectral window have been reported recently. In this chapter, the basic operation principles of a QWIP, and the design, fabrication, and characterization of multi-color and broadband QWIPs based on the GaAs/AlGaAs and InGaAs/AlGaAs material systems for the MW/LW/VLWIR applications are depicted.

Detection of terahertz radiation by GaAs transistor structures has been studied experimentally. The two types of samples under study included dense arrays of HEMTs and large-apertures detectors. Arrays consisted of parallel and series chains with asymmetric gate transistors for enhanced photoresponse on terahertz radiation. We investigated two types of wide-aperture detectors: grating gate detector, and single gate detector with bow-tie antenna. Wide-aperture detectors were symmetrical. Studies of transistor chains have shown that two essential features for this type of detector are the presence of asymmetry in the gate, and the type of connection between individual transistors themselves. Wide-aperture detectors have also been tested by narrow beams of terahertz radiation, which allows analyzing the role influence of individual parts of the detector for total sensitivity to terahertz excitation. The sensitivity and noise equivalent power of the detectors were evaluated.

A visible–extended shortwave infrared indium gallium arsenide (InGaAs) focal plane array (FPA) detector is the ideal choice for reducing the size, weight and power (SWaP) of infrared imaging systems, especially in low-light night vision and other fields that require simultaneous visible and near-infrared light detection. However, the lower quantum efficiency in the visible band has limited the extensive application of the visible–extended InGaAs FPA. Recently, a novel optical metasurface has been considered a solution for a high-performance semiconductor photoelectric device due to its highly controllable property of electromagnetic wave manipulation. Broadband Mie resonator arrays, such as nanocones and nanopillars designed with FDTD methods, were integrated on a back-illuminated InGaAs FPA as an AR metasurface. The visible–extended InGaAs detector was fabricated using substrate removal technology. The nanostructures integrated into the Vis-SWIR InGaAs detectors could realize a 10–20% enhanced quantum efficiency and an 18.8% higher FPA response throughout the wavelength range of 500–1700 nm. Compared with the traditional AR coating, nanostructure integration has advantages, such as broadband high responsivity and omnidirection antireflection, as a promising route for future Vis-SWIR InGaAs detectors with higher image quality.