Studies on Test and Evaluation of N~+ - P Junction Silicon Photo-Detectors for Space Qualification

摘要

Large area N~+ -P junction Si photo-detectors are fabricated using conventional Si foundry process and opto-electronic properties namely short circuit current density J_(sc) under AM0 illumination, dark current I_D, and spectral responsivity are characterized at different temperatures. It is observed that the shallow junction devices whose junction depths are 0.5 and 0.7 microns have J_(sc) equal to 36.0 and 40.0 mA/cm~2 respectively, and the corresponding I_D being respectively equal to or less than 44nA and 500 nA for an applied voltage of -2 V. The J_(sc) is found to be weakly dependent on temperature, over the range from 250 to 350 K which is in agreement with theory. The dark current of the devices is seen to vary in a nonlinear way with respect to temperature which has been supported theoretically. The electron damage coefficient of minority carriers is 7.8 x 10~(-11) for 8 MeV electrons, over a flux of 2 x 10~(13) electrons/cm~2. Environmental durability of the detectors is assessed as per the test conditions stipulated for space applications. It is observed that metallization bus bar and its structure are critical to produce durable detectors against adverse environmental conditions such as high temperature, thermal shock cycling and thermo vacuum baking. Devices with a tri-layer metallization coating, consisting of titanium, palladium and silver deposited by ion beam sputtering have been able to pass all the environmental tests specified for space qualification without any failure among the lot of devices.