High Performance of Midwave Infrared HgCdTe e-Avalanche Photodiode Detector

This letter reports on the design and fabrication of HgCdTe electron-avalanche photodiode (e-APD) for low dark current and high gain for imaging applications. HgCdTe e-APD photodiodes were fabricated in the n⁺-ν-p⁺ configuration for FPA at 30 μm × 30 μm pitch. Process for creating the required carrier profile and compositional grading in the absorption and multiplication regions was developed. Graded bandgap profile in the absorption region has been introduced. Shallow mesa etch isolation and effective passivation of side walls were introduced to control lateral currents. High quantum efficiency of 65% makes these APDs suitable for applications like quantum encryption. These measures helped in achieving high avalanche gain of 5550 at 8 V reverse bias in HgCdTe MWIR e-APD for the first time.