Characterization of gain and excess noise for mid-wavelength infrared HgCdTe electron avalanche photodiodes

HgCdTe electron avalanche photodiodes (e-APDs) with single-carrier multiplication hold great promise for weak signal detection. This work investigates the key metrics that affect the signal-to-noise ratio of mid-wavelength infrared (MWIR) Hg0.7Cd0.3Te e-APD: current, gain, and excess noise factor. The gain is over 1000 at -10 V, but the maximum useful gain is limited by the generation of band-to-band tunneling current at higher bias voltages. The gain dispersion obtained by characterizing the focal plane array is 4.7% at -7 V, indicating a relatively homogeneous gain from pixel to pixel. The excess noise factors evaluated by the noise power spectral density and the gain fluctuation methods both range from 1 to 1.32 at gains below 400, demonstrating the property of near excess-noise-free amplification of HgCdTe e-APDs.