High-performance, multispectral, and large-format infrared focal plane arrays are the long-demanded third-generation infrared technique for hyperspectral imaging, infrared spectroscopy, and target identification. A promising solution is to monolithically integrate infrared photodetectors on a silicon platform, which offers not only low-cost but high-resolution focal plane arrays by taking advantage of the well-established Si-based readout integrated circuits. Here, we report the first InAs/GaAs quantum dot (QD) infrared photodetectors monolithically integrated on silicon substrates by molecular beam epitaxy. The III–V photodetectors are directly grown on silicon substrates by using a GaAs buffer, which reduces the threading dislocation density to ∼106 cm–2. The high-quality QDs grown on Si substrates have led to long photocarrier relaxation time and low dark current density. Mid-infrared photodetection up to ∼8 μm is also achieved at 80 K. This work demonstrates that III–V photodetectors can directly be i...

https://pubs.acs.org/doi/pdf/10.1021/acsphotonics.6b00076

Monolithically Integrated InAs/GaAs Quantum Dot Mid-Infrared Photodetectors on Silicon Substrates

The paper presents progress in infrared (IR) detector technologies during 200 history of their development. Classification of two types of IR detectors (photon detectors and thermal detectors) is done on the basis of their principle of operation. The overview of IR systems and detectors is presented. Also recent progress in different IR technologies is described. Discussion is focused mainly on current and the most rapidly developing detectors: HgCdTe heterostructure photodiodes, quantum well AlGaAs/GaAs photoresistors, and thermal detectors. The outlook for near-future trends in IR technologies is also presented.

Infrared detectors: an overview

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Mercury Cadmium Telluride Growth Properties And Applications

Short-wave infrared (SWIR) detectors and emitters have a high potential value in several fields of applications, including the internet of things (IoT) and advanced driver assistance systems (ADAS), gas sensing. Indium Gallium Arsenide (InGaAs) photodetectors are widely used in the SWIR region of 1–3 μm; however, they only capture a part of the region due to a cut-off wavelength of 1.7 μm. This study presents an InAs p-i-n photodetector grown on a GaAs substrate (001) by inserting 730-nm thick InxAl1−xAs graded and AlAs buffer layers between the InAs layer and the GaAs substrate. At room temperature, the fabricated InAs photodetector operated in an infrared range of approximately 1.5–4 μm and its detectivity (D*) was 1.65 × 108 cm · Hz1/2 · W−1 at 3.3 μm. To demonstrate performance, the Sherlock Holmes mapping images were obtained using the photodetector at room temperature.

/pdf/inas-on-gaas-photodetectors-using-thin-inalas-graded-buffers-55x95jmnha.pdf

InAs on GaAs Photodetectors Using Thin InAlAs Graded Buffers and Their Application to Exceeding Short-Wave Infrared Imaging at 300 K.

Optical and electrical studies of arsenic–implanted HgCdTe films grown with molecular beam epitaxy on GaAs and Si substrates

The development and fabrication of extended short-wavelength infrared (SWIR) HgCdTe (MCT) sensors grown on CdTe/Si substrates is reported. The MCT epilayers were grown on CdTe/Si substrates by molecular beam epitaxy (MBE). The epilayers were evaluated using Fourier transform infrared spectroscopy (FTIR), X-ray double crystal rocking curve (DCRC), Van der Pauw Hall measurements, dislocation defect–decoration etching and Nomarski microscopy. The FTIR analysis revealed a cutoff wavelength of 2.25 μm at 300 K which corresponds to a cadmium composition of 47%. As-grown epilayers have void defect densities less than 10 3  cm −2 and etch pit densities of ∼1 × 10 7  cm −2 . The Hall mobilities of annealed MCT samples are on the order of 1500 cm 2 /Vs and have carrier concentrations of ∼1 × 10 16  cm −3 at 300 K. Samples were doped in situ with indium (donor) and ion-implanted with arsenic (acceptor) to fabricate p–n diodes with sizes ranging from 15 μm to 250 μm diameter. We present the results and analysis of temperature dependent current–voltage ( I – V ) and quantum efficiency/responsivity measurements on the p–n diodes. In our analysis, we found that the I – V characteristics of small devices were dominated by shunt currents and quantum efficiency is limited by Shockley–Read–Hall (SRH) mechanisms.

Development and fabrication of extended short wavelength infrared HgCdTe sensors grown on CdTe/Si substrates by molecular beam epitaxy

Growth of ZnTe on Si using molecular beam epitaxy (MBE) has been pursued as a new approach for a lattice-matched, large-area, low-cost alternate substrate for both II–VI and III–V compound semiconductors with lattice constants very near 6.1 A, such as HgCdSe and GaSb-based type II strained-layer superlattices. In this paper, we report our findings on the systematic study of MBE growth parameters for both ZnTe(211) on Si(211) and ZnTe(100) on Si(100). Near-optimal growth procedures have been established for producing ZnTe/Si wafers with high crystallinity, low defect and etch pit densities, as well as excellent surface morphology. Using this baseline MBE growth process, we obtained ZnTe(211)/Si wafers with x-ray full-width at half-maximum as low as 70 arcsec.

MBE-Grown ZnTe/Si, a Low-Cost Composite Substrate

The HgCdTe(MCT) grown on CdTe/Si substrate has a high dislocation density due to lattice mismatch. Thermal cycle annealing (TCA) is effective in reducing the dislocation density. The TCA at high temperatures results in inter-diffusion of the constituent elements across the MCT/CdTe interface. In␣this study, we observed a reduction in dislocation density with good surface morphology due to proper design of the TCA system, low annealing temperature, and large number of annealing cycles. The ampoule containing the samples is placed in direct contact with the graphite heating tube which helps in increasing the heating and cooling rates of the annealing cycle. To maintain Hg overpressure, Hg is placed in the sample holder, instead of in the ampoule to avoid Hg condensation. The best results were obtained by cycling the annealing temperature between 290°C and 350°C. Anneals were performed by using 32, 64, 128 and 256 cycles. We obtained an etch pit density (EPD) as low as 1 × 106 cm−2. Lower EPD was not achieved either by increasing annealing temperature or number of annealing cycles. Through secondary ion mass spectroscopy analysis, we observed very little inter-diffusion of Cd across the MCT/CdTe interface for the 128 cycle annealing. These results show promise in bridging the gap in the device performance between the MCT material grown on CdTe/Si and CdZnTe substrates.

Low Temperature, Rapid Thermal Cycle Annealing of HgCdTe Grown on CdTe/Si

Mercury cadmium telluride (MCT) epilayers have been grown on CdTe/Si using molecular beam epitaxy and 8-μm-deep mesa structures formed using plasma etching. Following previous work done on etching mesas and subjecting material to thermal cycle annealing, we set out to determine the limits and underlying physics of dislocation reduction in mesa-etched and annealed MCT. This paper describes the dependence of dislocation reduction on anneal time, cycle annealing, temperature, and etch depth. We show dislocation density reduction below 3 × 105 cm−2 in 10-μm-wide, long-bar mesas along the \( [0\bar{1}1] \) orientation with only a 5-min anneal at 400°C.

Dislocation Reduction in HgCdTe Mesa Structures Formed on CdTe/Si

Arsenic ion-implantation is a standard device processing step to create selective area p+-HgCdTe (MCT) regions in planar devices. One of the issues associated with the ion-implantation process is the significant structural damage to the MCT epilayer. These structural defects limit the performance of diodes via significant tunneling reverse-bias dark currents. After ion-implantation, a high temperature annealing step is required to activate the implant (arsenic) by moving it into the tellurium sublattice and also to heal the lattice damage caused by the implantation process. In this study, we have used thermal cycle annealing (TCA) to decrease ion implantation damage. In TCA, we rapidly heat and cool an MCT sample, which provides an additional degree of freedom that is not obtainable with conventional annealing. We have successfully performed TCA for dislocation defect reduction in in-situ indium-doped MCT with limited inter-diffusion between the absorber layer and cadmium rich cap layer. We also investigated the application of TCA to arsenic ion-implanted MCT. Defects were studied using scanning electron microscopy (SEM) after subjecting the samples to Benson etching to decorate the defects. Mercury-deficient and tellurium-saturated overpressure anneals were performed in an attempt to increase mercury vacancy concentrations and, thereby, increase dislocation climb. Such anneals significantly increased the etch pit density (EPD) in both ion-implanted and un-implanted MCT. By cycle annealing, we have also shown EPD reduction in arsenic ion-implanted, long bar shaped MCT mesas formed on CdTe/Si substrates.

Sina Simingalam

Papers

Development and fabrication of extended short wavelength infrared HgCdTe sensors grown on CdTe/Si substrates by molecular beam epitaxy

MBE-Grown ZnTe/Si, a Low-Cost Composite Substrate

Low Temperature, Rapid Thermal Cycle Annealing of HgCdTe Grown on CdTe/Si

Dislocation Reduction in HgCdTe Mesa Structures Formed on CdTe/Si

Thermal cycle annealing and its application to arsenic-ion implanted HgCdTe