Linear-Mode HgCdTe Avalanche Photodiodes for Photon-Counting Applications

An overview of recent improvements in our understanding of, and the maturity of, linear-mode photon counting with the HgCdTe electron-initiated avalanche photodiode is presented. In 2010 DRS fabricated an experimental 2 × 8 array with (64 μm)2 pixels which enabled, for the first time, linear-mode photon counting by use of the MWIR cutoff HgCdTe electron-initiated avalanche photodiode. The device had a high single-photon signal-to-noise ratio of 13.7, an excess noise factor of 1.3–1.4, a 7 ns minimum time between events, and a broad spectral response extending from 0.4 μm to 4.2 μm. DRS recently fabricated a new set of devices with improved yield and performance compared with the first device: the false event rate was reduced by a factor of almost 10 to 150 kHz, the photon detection efficiency was increased from 50% to >60%, and the APD gain was increased by a factor of 4 to over 1900.