Pn Junction Photoelectric Characterization And Analysis Of Long-wavelength HgCdTe Infrared Detection Arrays

Infrared focal plane array detector has been widely used in military and civilian fields due to its high resolution,strong anti interference ability and strong penetrability.Mercury cadmium telluride is the standard material to fabricate high-performance infrared focal plane array?FPA?detectors.However,etch-induced damage is a serious obstacle for realizing highly uniform and damage-free FPA detectors.In this Letter,the high signal-to-noise ratio and high spatial resolution scanning photocurrent microscopy?SPCM?is used to characterize the dry etch-induced damage inversion layer of vacancy-doped p-type Hg_1-xCd_xTe?x=0.22?material under different etching temperatures.It is found that the peak-to-peak magnitude of the SPCM profile decreases with a decrease of etching temperature,showing direct proof of controlling dry etch-induced type conversion.Our work paves the way toward seeking optimal etching processes in large-scale infrared FPAs.We have also studied the n-on-p junction by B+ implantation by the method of SPCM without damage in situ combined with Sentaurus TCAD,and finally,we obtain some innovative conclusions:1.Based on the SPCM method,we prepare Hg Cd Te sample and extract p-n junction depth of the etched groove is 2.6 mm,2.1mm,1.6 mm and 1.2 mm under etching temperatures of 273 K,223 K,173 K and 123 K respectively.The simulated SPCM signal profile curves with fitted electron concentrations in the converted n-type region are in a good agreement with that of the experimental data.The phenomenon of decreasing peak to peak magnitude of the SPCM profile as a function of decreasing etching temperature is caused by different electron concentrations in the converted n-type region,and the depth of n type conversion region increases with increasing temperature.2.The mid-wavelength?x=0.30?Hg Cd Te device is still n-on-p structure at high temperature,and n type extension has no relation with temperature and size of pixel.3.Junction transformation: The long-wavelength?x=0.22?Hg Cd Te device is n-on-p structure at low temperature,and it becomes n-on-n-structure at mid temperature?100K-150K?,while,it becomes n--on-n-on-n-structure at higher temperature?150K-290K?.And the minority carrier diffusion length becomes shorter with increasing temperature,because the recombination center is activated with increasing temperature,resulting in minority carrier life decreasing.The extracted traps energy level of B+ implantation region is about 37.63 me V,and this value is approximately one third of bandgap of vacancy-doped p type Hg_1-xCd_xTe?x=0.22?.