Polarization enhanced GaN separate absorption and multiplication ultraviolet avalanche photodiodeswith an ScGaN interlayer

This article proposes a separate absorption and multiplication (SAM) GaN-based avalanche photodiode (APD) that achieves both high gain and low operating voltage by applying Sc-based ferroelectric material ScGaN in APDs. The avalanche gain of the proposed SAM APD with a low Sc composition p-ScGaN insertion layer reaches 7.2 × 10⁴, which is 60% higher than that of a conventional p-i-p-i-n GaN-based APD. This improvement can be ascribed to the enhanced carrier transport properties induced by the polarization electric field. Meanwhile, the operating voltage is reduced from 77 V to 72 V. Furthermore, as the insertion layer has a significant impact on the internal electric field intensity and the band structure in APD devices, the doping concentration and thickness of the interlayer are optimized. The proper utilization of low Sc composition shows low lattice mismatch and high polarization, indicating the potential for further applications of ScGaN in photoelectric devices in the future.