Bandgap engineering of Gallium oxides by crystalline disorder

Abstract

Gallium oxide (Ga2O3) has recently emerged as a promising candidate for applications in high-power and radio frequency electronics, deep-ultraviolet optoelectronics, etc. The engineering of bandgap and constructing of heterostrucutres are fundamental steps towards such applications. However, efficient bandgap engineering of Ga2O3 is still a huge challenge. Herein, by the combination of experiments and first-principles calculations, we report that the oxygen vacancy (VO) density and crystalline disorder of the Ga2O3 can be tuned continuously by modulating the O/Ga ratio during the growth process. The VO can introduce localized defect states right above the valence band, thus improving the conductivity of the films. While the crystalline disorder can lead to the shift of the valence band towards the conduction band, thus narrowing the bandgap of the Ga2O3 significantly. As a demonstration of the practical applications of the bandgap engineering by the crystalline disorder, Ga2O3-based deep-ultraviolet homojunction photodetectors have been developed. The device shows a peak responsivity of 22.1 mA/W and a detectivity of 8.7 × 1012 Jones at 0 V bias, which are among the best values for zero-biased Ga2O3 photodetectors. The present findings on tuning the bandgap of Ga2O3via structural disorder are expected to pave a new avenue to achieving high performance Ga2O3 optoelectronic and electronic devices.