High Performance of SWIR HgCdTe Photovoltaic Detector Passivated by ZnS

Abstract

Short wave infrared (SWIR) photovoltaic devices have been fabricated from metal orgnic vapour phase epitaxy (MOVPE) grown n- on p- HgCdTe films on GaAs substrates. The MOVPE grown films were processed into mesa type discrete devices with wet chemical etching employed for meas delineation and ZnS deposited from evaporated from effusion cell in an ultra high vacuum (UHV) chamber. The main features of the ZnS deposited from effusion cell in UHV chamber are low fixed surface charge density, and small hysteresis. It was found that a negative flat band voltage with -0.6V has been obtained for Metal Insulator Semiconductor (MIS) capacotor which was evaporated at 910 ℃ for 90 min. Current-Voltage (I-V) and temperature dependence of the I-V characteristics were meadured in the temperature range 80-300 K. The Zero bias dynamic resistance-area product (R0A) was about 7500 Ω-㎠ at room temperature. The physical mechanisms that dominate dark current properties in the HgCdTe photodiodes are examined by the dependence of the R0A product upon reciprocal temperature. From theorretical considerations and known current expressions for thermal and tunnelling process, the devices is shown to be diffusion limited up to 180 K and g-r limited at temperature below this.