Study Of Fabrication And Damage Evaluation For HgCdTe Photocoductive Detectors

Hg1-xCdxTe is a kind of is one of narrow bandgap semiconductor, which is considered to be the most important material for fabricating infrared detector. HgCdTe infrared detector plays an important role in remote sensing, night vision, communication, monitoring, etc. Fabricating processing takes an important impact on the performance of detectors. As the increasingly demand of high performance device, more and more efforts have been paid to promote the processing for fabricating high performance devices. Focused on reducing the damage of fabricating processing, we report demonstration of polishing and dry etching in fabrication of HgCdTe photoconductive device.Ⅰ. Orthogonal experiment was employed to investigate the effect of polishing conditions to subsurface damage of HgCdTe materials. Polishing conditions of loading jig weight, polishing time and polishing speed in both Mechanical Polishing and Chemical Mechanical Polishing were studied in contact with the depth of subsurface damage. The influence level and optimal polishing conditions were obtained. And regression analysis was employed to obtain the regression equation between the polishing conditions and the depth of subsurface damage, which provide a reference for optimizing the polishing process and predicting the degree of sub-surface damage.Ⅱ. The effects of subsurface damage generated on polishing to HgCdTe material and photoconductive device performance has been investigated. Minority carrier lifetime of HgCdTe material was obtained by Microwave Reflection Photoconductive Decay (MRPCD) method and we found that with the depth of removed subsurface damage increased a substantial improve on the minority carrier lifetime of HgCdTe material was obtained. Mobility and carrier concentration of HgCdTe material was measured by temperature-dependent Hall measurement. It was found that defects and impurities induced ionized impurity scattering resulted in an increasing of carrier concentration, and a decreasing of mobility in the low temperature. In comparison of two HgCdTe photoconductive devices with different subsurface damage depth, we found that photoconductive devices without subsurface damage had a lower temperature corresponding to the inflection point resistance, a significantly improved short-wave spectral response, noise, responsivity and detectivity.Ⅲ. The effect of dry etching of HgCdTe photoconductive device performance was investigated. Ion Beam Milling (IBM) and Inductively Coupled Plasma (ICP) etching were employed to fabricate two HgCdTe photoconductive devices. Magnetic-field-dependent and temperature-dependent Hall measurements was conducted to obtain mobility spectrum. Different scattering mechanisms were analyzed on the basis of the fitted mobility and temperature. And optoelectronic performance also improved that ICP etched HgCdTe photoconductive device had a better performance. Temperature reliability measurement was conducted to evaluate the performance of ICP and IBM etched HgCdTe photoconductive devices. Disappearance or increase of the defects in the material at high temperature led to different performances of ICP and IBM etched HgCdTe photoconductive devices in the process.