Monte Carlo Simulation of High-Speed MWIR HgCdTe e-APD

High-speed avalanche photodiodes (APDs) have attracted great interest for their potential applications in weak signal detection and free-space communication. In this article, the bandwidth characteristics of mid-wavelength infrared (MWIR) Hg
_0.7
Cd
_0.3
Te electron-APDs (e-APDs) are investigated by the Monte Carlo method. The simulated gain, excess noise, and carrier velocity agree well with the previously reported experimental data. Moreover, the transport process of photogenerated carriers is described in detail. Meanwhile, the effects of different absorption region thickness as well as the incident wavelengths on the device bandwidth are studied, and the trend of the bandwidth with bias voltage is explained. Finally, a structure with gradient
${p}$
-region is proposed to further increase the bandwidth.