Short-wave infrared InGaAs photodetectors and focal plane arrays

In this article, unique spectral features of short-wave infrared band of 1 μm–3 μm, and various applications related to the photodetectors and focal plane arrays in this band, are introduced briefly. In addition, the different material systems for the devices in this band are outlined. Based on the background, the development of lattice-matched and wavelengthextended InGaAs photodetectors and focal plane arrays, including our continuous efforts in this field, are reviewed. These devices are concentrated on the applications in spectral sensing and imaging, exclusive of optical fiber communication.

Etching mask optimization of InAs/GaSb superlattice mid-wavelength infared 640×512 focal plane array

In this paper we focused on the mask technology of inductively coupled plasma（ICP） etching for the mesa fabrication of infrared focal plane arrays（FPA）.By using the SiO_2 mask,the mesa has higher graphics transfer accuracy and creates less micro-ripples in sidewalls.Comparing the IV characterization of detectors by using two different masks,the detector using the SiO_2 hard mask has the R_0A of 9.7×10~6 Ω·cm^2,while the detector using the photoresist mask has the R_0A of3.2 × 10~2 Ω·cm^2 in 77 K.After that we focused on the method of removing the remaining SiO_2 after mesa etching.The dry ICP etching and chemical buffer oxide etcher（BOE） based on HF and NH4 F are used in this part.Detectors using BOE only have closer R_0A to that using the combining method,but it leads to gaps on mesas because of the corrosion on AlSb layer by BOE.We finally choose the combining method and fabricated the 640×512 FPA.The FPA with cutoff wavelength of 4.8 μm has the average R_0A of 6.13 × 10~9 Ω·cm^2 and the average detectivity of 4.51 × 10~9 cm·Hz^（1/2）.W^（-1）at 77 K.The FPA has good uniformity with the bad dots rate of 1.21%and the noise equivalent temperature difference（NEDT） of 22.9 mK operating at 77 K.

MBE HgCdTe:A Challenge to the Realization of Third Generation Infrared FPAs

Some results on the molecular-beam epitaxial growth of HgCdTe focusing on the requirements of the 3rd generation infrared focal plane arrays are described. Good uniformity is observed over 75mm HgCdTe epilayers,and the deviation in cutoff wavelength is within 0. 1μm at 80K. A variety of surface defects are observed and the formation mechanism is discussed. The average density of surface defects in 75mm HgCdTe epiluyers is found to be less than 300cm^-2. It is found that the surface sticking coefficient of As during HgCdTe growth is very low and is sensitive to growth temperature, being only -1 × 10^-4 at 170℃. The activation energy of As in HgCdTe was determined to be 19.5meV,which decreases as （Na - Nd）^1/3 with a slope of 3.1 × 10^-5 meV · cm. The diffusion coefficients of As in HgCdTe of 1.0 ± 0,9 × 10^-16,8 ± 3 × 10^- is, and 1.5 ± 0.9 × 10^-13 cm^2/s are obtained at temperatures of 240,380, and 440℃, respectively under Hg-saturated pressure. The MBE-grown HgCdTe is incorporated into FPA fabrications,and the preliminary results are presented.

128×128 element PtSi infrared CCD image sensor

A new 128×128 element PtSi Schottky barrier infrared image sensor with ITCCD readout structure and PtSi thin film optical cavity detector structure has been fabricated,which has 50μm×50 μm pixels,a fill factor of 40 percent,the nonuniformity of 5% or less and the dynamic range of over or equal to 50 dB.The noise equivalent temperature difference is 0.2 K with f/1.0 optics at 300 K background. In this paper,the principle of operation,design consideration and fabrication technology for the device are described.

The theory and experiment of very-long-wavelength 256×1 GaAs/Al_(x)Ga_(1-x)As quantum well infrared detector linear arrays

The 256×1 linear array of multiple quantum wells infrared photodetector (QWIP) is designed and fabricated for the peak response wavelength at λP=14.6 μm. The response spectral width is bigger than 2.2 μm. The two-dimensional (2D) diffractive coupling grating has been formed on the top QWIP photosensitive pixel for coupling the infrared radiation to the infrared detective layers. The performance of the device at VB=3 V and T=45 K has the responsibility 4.28×10-2 (A/W), the blackbody detectivity Db*=5.14×109 (cm·Hz1/2/W), and the peak detectivity Dλ*=4.24× 1010 (cm·Hz1/2/W). The sensor pixels are connected with CMOS read out circuit (ROC) hybridization by indium bumps. When integral time is 100 μs, the linear array has the effective pixel of QWIP FPA Nef of 99.2%, the average responsibility  (V/W) of 3.48×106 (V/W), the average peak detectivity Dλ* of 8.29×109 (cm·Hz1/2/W), and the non-uniformity UR of 5.83%. This device is ready for the thermal image application.

Thermoelectric infrared detectors:Design,fabrication,and performance assessment

This study presents a comprehensive optimization and comparative analysis of thermoelectric(TE)infrared(IR)detec-tors using Bi_(2)Te_(3) and Si materials.Through theoretical modeling and numerical simulations,we explored the impact of TE mate-rial properties,device structure,and operating conditions on responsivity,detectivity,noise equivalent temperature difference(NETD),and noise equivalent power(NEP).Our study offers an optimally designed IR detector with responsivity and detectivity approaching 2×10^(5) V/W and 6×10^(9) cm∙Hz^(1/2)/W,respectively.This enhancement is attributed to unique design features,includ-ing raised thermal collectors and long suspended thin thermoelectric wire sensing elements embedded in low thermal conductivity organic materials like parylene.Moreover,we demonstrate the compatibility of Bi_(2)Te_(3)-based detector fabrication pro-cesses with existing MEMS foundry processes,facilitating scalability and manufacturability.Importantly,for TE IR detectors,zT/κemerges as a critical parameter contrary to conventional TE material selection based solely on zT(where zT is the thermoelec-tric figure of merit andκis the thermal conductivity).