Study on area-dependent multiplication region width and optimization of HgCdTe avalanche focal plane

Abstract

Linear-mode HgCdTe avalanche photodiodes (APDs) have attracted significant attention due to their exceptionally low excess noise, operational bias ranging from −12 to 0 V, and linearly tunable gain. These characteristics suggest promising future applications in optical observations. The design of the multiplication region based on the PIN structure is critical, as it directly influences the photoelectric properties of the device, including gain and excess noise. This paper primarily investigates the effect of implanted areas on the multiplication region and examines area-related gain and noise characteristics of mid-wavelength infrared (MWIR) HgCdTe APDs at a temperature of 80 K. Studies conducted on diodes with varying implanted areas indicate that those with larger implanted areas create a wider multiplication region, which leads to lower gain and higher excess noise factors. Finally, 30 μm pitch 640 × 512 array HgCdTe APDs for cut-off wavelengths 4.8 µm at 80 K corresponding to compositions x_Cd = 0.31 were fabricated. The number of noise bad pixels and the band-to-band tunneling (BBT) current have been significantly reduced due to the optimized the multiplication region width. Consequently, high-definition imaging under short integration times has been successfully achieved.