Performance of Mid-Wave Infrared HgCdTe e-Avalanche Photodiodes

HgCdTe has been shown to be the first semiconductor exhibiting single-carrier multiplication in avalanche photodiodes (APDs) up to multiplication factors larger than 1000 and with close to zero excess noise. These results have opened a new horizon for low-flux and/or versatile imaging from visible wavelengths up to the infrared cutoff wavelength of the APDs. In this paper we report the first results on mid-wave infrared (MWIR) cutoff wavelength APDs manufactured at Sofradir in collaboration with CEA-LETI. These APDs display high gain and low dispersion on and between wafers. In particular, a record avalanche gain M of over 10,000 is observed for some diode structures. This result provides an additional demonstration of the stability of single-carrier multiplication in HgCdTe and shows that the technological processes used at Sofradir are well adapted to APD manufacturing. A dedicated readout integrated circuit (ROIC) with 384 × 288 format and l5 μm pitch was developed to address both passive amplified imaging and active laser-assisted imaging. Arrays were produced using p-type HgCdTe films grown by liquid-phase epitaxy on CdZnTe substrates. Focal-plane array (FPA) performance is reported for ROICs hybridized with APD arrays manufactured at Sofradir. Operability of the best devices exceeds 99.7% for gains up to 55. Relative dispersions of the gain and ROIC output voltage are lower than 4%. The excess noise factor is lower than 1.4 over this range of gains.