9 February 2009 Vacuum baking effects on the I-V characteristics of LWIR HgCdTe photodiodes with different passivation
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Abstract
HgCdTe infrared detector is designed to operate at cryogenic temperatures, so vacuum baking is a required process for out-gassing in packaging of devices. As HgCdTe material, as well as ZnS passivation layer is sensitive to heat induced changes, this process may be problematical for HgCdTe devices even at relatively low temperatures. We try to solve the problems of heat instability by the fabrication of CdTe/ZnS double passivation layers. The effect of vacuum baking is investigated through current-voltage (I-V) characteristics. We have compared the effects on devices with different passivation layers. We have also compared the photodiodes fabricated on MBE grown HgCdTe on GaAs substrates and LPE grown HgCdTe on CdZnTe. The devices were passivated with electron beam evaporated CdTe and ZnS and the p-n junction was formed by ion-implantation. Through the analysis of I-V characteristics, we found that the devices passivated with ZnS cannot afford vacuum baking even at 70°C, while the CdTe/ZnS- passivated devices can afford up to 110°C temperature and the performance improved. After only 4 hours baking, the dynamic resistance of ZnS passivation devices began to decrease and 10 hours later the zero-bias dynamic resistance (R0) decreased nearly 3 times. Further baking of 110°C sees the maximum dynamic resistance of CdTe/ZnS passivation devices increase 2 to 4 times. An insight into the mechanisms and parameters that are affected by vacuum baking is also gained by resistance-voltage (R-V) curve fitting. The results also indicated the baking effects on LPE grown HgCdTe devices are almost same to MBE grown HgCdTe devices.
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Yi Deng, Yi Deng, Fei Ying, Fei Ying, Xin-guo Cheng, Xin-guo Cheng, Zheng-hua Ye, Zheng-hua Ye, Xiao-ning Hu, Xiao-ning Hu, } "Vacuum baking effects on the I-V characteristics of LWIR HgCdTe photodiodes with different passivation", Proc. SPIE 7158, 2008 International Conference on Optical Instruments and Technology: Microelectronic and Optoelectronic Devices and Integration, 715808 (9 February 2009); doi: 10.1117/12.807058; https://doi.org/10.1117/12.807058
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