Temperature-Driven Pre-Avalanche Dark Current Mechanisms in MWIR HgCdTe Photodiodes via Electrothermal Mapping and Optimization Strategies

Mid-wavelength infrared (MWIR) HgCdTe avalanche photodiodes (APDs), aimed at high-operating-temperature (HOT) infrared detection, suffer from a rapidly increasing dark current as temperature rises, which markedly limits their performance. This work employs an experimentally calibrated electrothermal numerical analysis framework with spatially resolved quasi-3D mapping to investigate the dark current mechanisms, the temperature-dependent evolution, and the photocurrent gain of a planar N-on-P Hg0.7Cd0.3Te APD over the 80–300K range. The results show that the pre-avalanche dark current surge originates from an electron channel at the N${}^{-}$/P+junction corners, accompanied by localized lattice temperature hotspots that promote premature breakdown. Guided by this insight, we propose and validate three structural optimization strategies: the high-doping absorption layer, the high-Cd above layer, and the electron injection block layer, all of which effectively improve HOT performance by suppressing the electron-channel formation. We also facilitate the Okuto–Crowell (O–C) model by fixing the power-law exponent$n$and approximating$A$($T$) and$B$($T$) as linear functions of temperature. The analysis further shows that the dominant dark current mechanism transitions from Shockley–Read–Hall (SRH) generation below 160 K to drift-diffusion (D-D) current and Auger generation at higher temperatures, and that the extracted SRH lifetimes and interface trap densities agree with experimentally determined values. Collectively, this research establishes a practical framework for the development of HOT MWIR HgCdTe APD.