Al0.1Ga0.9N p-i-n Ultraviolet Avalanche Photodiodes With Avalanche Gain Over 106

We report Al0.1Ga0.9N p-i-n ultraviolet (UV) avalanche photodiodes (APDs) based on sapphire substrates with a record-high gain over 2 x 10(6). The devices fabricated with various mesa diameters present consistent avalanche behaviors and identical dark current distributions over multiple I - V scans, which are comparable to the GaN APDs grown on free-standing GaN substrates. The quadratic fitting of the dark currents versus the mesa sizes reveals that the leakage current at the breakdown voltage is a mixture of surface leakage and bulk leakage, and the surface component is comparable to that of the bulk. Additionally, KOH surface treatment and SiO2 passivation are proven to be very effective in suppressing the leakage current and achieving robust avalanche performance.

Automated summary

In this research, Al0.1Ga0.9N p-i-n ultraviolet avalanche photodiodes (APDs) based on sapphire substrates were reported, achieving a record-high gain over 2 x 10(6). The devices fabricated with various mesa diameters demonstrated consistent avalanche behaviors and identical dark current distributions, comparable to GaN APDs grown on free-standing GaN substrates. Quadratic fitting analysis revealed that the leakage current at the breakdown voltage is a mixture of surface and bulk leakage, with the surface component comparable to the bulk. Additionally, KOH surface treatment and SiO2 passivation were proven effective in suppressing the leakage current and achieving robust avalanche performance.