Highly selective ozone-treated β -Ga2O3 solar-blind deep-UV photodetectors

Abstract

The ultra-wide energy bandgap (4.6–4.9 eV) of the β-Ga2O3 semiconductor offers intrinsic solar blindness, which is a great advantage as the absorber material of a deep ultraviolet (UV) photodetector. Although the band-to-band excitation transition in β-Ga2O3 is allowed solely by the UV-C wavelength, the defective sites including oxygen vacancies can induce sub-bandgap absorption, resulting in high background noise. The UV-ozone treatment was performed at elevated temperatures to investigate its effect on removing these oxygen vacancies; it creates reactive oxygen radicals that can reach the β-Ga2O3 lattice and passivate the defective sites. The chemical analysis through x-ray photoelectron and micro-Raman spectroscopies revealed an increase in Ga–O bonding after UV-ozone treatment. The optoelectrical measurements on the β-Ga2O3 UV-C photodetectors showed that the UV-ozone treatment significantly decreased the response to UV-A light. Thus, the photodetector performance (photo-to-dark current ratio, responsivity, detectivity, and rejection ratio) was greatly enhanced; especially, the rejection ratio was increased to 4.56 × 108 by eight orders of magnitude after UV-ozone treatment. The remarkably improved UV-C selectivity in the β-Ga2O3 solar-blind photodetector highlights its potential of realizing truly solar-blind photodetectors using a simple UV-ozone treatment technique.