Discussion on diffusion current suppression in HgCdTe MWIR detectors

One limitation of dark current for HOT HgCdTe MWIR detector is diffusion current related to Auger generation mechanisms. However, this limit can be overcame using a fully depleted P-i-N diode structure. On the way toward PIN structures, we discuss on the impact of Auger suppression on partially fully-depleted photodiodes. Indeed, we report dark current evolution with temperature following a diffusion trend line but also a dark current decreasing when increasing the applied voltage in the temperature range 120-180K on the same detector. If the SRH current in the space charge region is very low, an Auger suppression mechanism should result in a decrease of the total dark current when depleting a larger volume of the pixel on such detector. This hypothesis could match with the reported dark current data obtained on detectors manufactured at CEA LETI and Lynred. They are based on p/n diodes, 7.5μm pitch arrays connected as 2x2 super-pixels to a 15μm pitch ROIC (640x512 VGA format).