【Device Papers】Investigation of Impact Ionization Variations Versus Electric Field and Temperature in Compound Semiconductors for UV-APD Applications

      Researchers from the Amirkabir University of Technology have published a dissertation titled "Investigation of Impact Ionization Variations Versus Electric Field and Temperature in Compound Semiconductors for UV-APD Applications" in 2025 33rd International Conference on Electrical Engineering (ICEE).

Abstract

      This paper investigates the impact ionization coefficients for two types of carriers, electrons and holes, using the Okuto–Crowell model and related equations. We studied how these coefficients depend on electric field and temperature in various sample materials, specifically GaN, AlₓGa₁₋ₓN, 4H-SiC, and Ga₂O₃, which are suitable for ultraviolet avalanche photodiode (APD) applications. These materials are highly suitable for ultraviolet photodetectors due to their wide bandgap, which places them in the ultraviolet light absorption range. As a result, expensive filters customarily required for high-sensitivity ultraviolet detectors are not necessary. A typical architecture for ultraviolet detectors is the Separate Absorption and Multiplication (SAM) structure, which consists of two regions: the absorption region (A) and the multiplication region (M). Therefore, investigating the materials used in these regions is crucial from multiple perspectives. Selecting materials with high ionization coefficients at elevated temperatures and electric fields in the multiplication region is important. In our study, based on the coefficients from the Okuto–Crowell model, GaN exhibits exceptionally high ionization coefficients, approximately αₑ = 10 × 10⁶ and αₕ = 8 × 10⁵ at an electric field of 5 MV/m and a temperature of 450 K. Additionally, at very low temperatures (~300 K), materials such as GaN and AlₓGa₁₋ₓN can exhibit impact or avalanche ionization due to their crystal lattice structure. In contrast, 4H-SiC and Ga₂O₃ do not demonstrate avalanche conditions at this temperature. Finally, our analysis results are largely consistent with some of the experimental results reported in [20]; however, slight differences arise from the determination of the input parameters in the Okuto–Crowell equation.

DOI：

https://doi.org/10.1109/ICEE67339.2025.11213647