Bandwidth Characteristics of Mid-Wavelength Infrared PIN HgCdTe Avalanche Photodiodes

HgCdTe avalanche photodiodes (APDs) are used in mid-wavelength infrared (MWIR) photoelectric detectors in free-space optical communication, three-dimensional light detection, and ranging. Although HgCdTe has a small electronic effective mass and high mobility, there is a gap between the actual bandwidth of the device and the theoretical limit, and it is important to analyze the carrier transport mechanism in these devices. A two-dimensional finite element model is used to analyze the carrier transport mechanism for different device structures and bias voltages. The structural parameters of the device are optimized on the basis of a comprehensive determination of its bandwidth characteristics. Experimental data and calculation results are found to be consistent. This structural optimization increases the device bandwidth from 27.1 MHz to 553 MHz, with a gain-normalized dark current density (GNDCD) of less than 10−6 A/cm2. The results obtained here can provide guidance for the design of high-speed HgCdTe devices.