Ferroelectric polarization-enhanced back-illuminated GaN-based ultraviolet avalanche photodiodes with a ScGaN...

This paper proposes a back-illuminated separated absorption and multiplication (SAM) structure photodiode based on ferroelectric scandium gallium nitride (ScGaN), which improves the problems of low gain and high operating voltage in conventional gallium nitride (GaN)-based ultraviolet avalanche photodiodes (APDs). Upon introducing an n-type ScGaN interlayer into the device, the strong polarization effect contributes to the enhancement of the built-in electric field. In comparison with conventional p-i-n-i-n GaN-based APDs, the designed back-illuminated device shows a 56% enhancement in avalanche gain to 9.2 × 10⁴ and a decrease in avalanche breakdown voltage from 72 V to 64 V. According to analysis of the internal electric field and band structure, this paper explains the physical mechanism behind the performance enhancement and further optimizes the thickness and doping concentration parameters of the n-ScGaN interlayer. The proper utilization of results will greatly advance ScGaN's potential for future applications in optoelectronic devices.