Electronic properties and photo-gain of UV-C photodetectors based on high-resistivity orthorhombic Κ-Ga2O3 epilayers

Electrical and optical properties of nominally-undoped high-resistivity kappa-Ga2O3 epitaxial films are presented, along with the ultraviolet detection performance of solar-blind photodetectors fabricated from these epilayers. The photodetectors exhibited a solar-blind rejection ratio higher than 104, reproducible on-off switching times and a remarkable photo-gain (up to 103). The latter can be ascribed to either a strong trapping effect of free holes by deep levels inducing a majority carrier excess Delta n with respect to the minority carriers Delta p, or to a hole mobility several orders of magnitude lower than the electron mobility, both the hypothesis being consistent with literature data. A saturation of the gain, dependent on detector size, was observed beyond a certain applied voltage, that is consistent with a minority carrier diffusion length of a few 10-5 cm. Non-critical growth conditions, reproducibility and intrinsic spectral selectivity together with good UV -detection performance make kappa-Ga2O3 a suitable material for solar-blind ultraviolet photodetectors.

Automated summary

The electrical and optical properties of high-resistivity kappa-Ga2O3 epitaxial films are studied, and their performance as solar-blind photodetectors is investigated. The photodetectors exhibit a high rejection ratio, reproducible on-off switching times, and significant photo-gain. The material shows non-critical growth conditions, intrinsic spectral selectivity, and good UV-detection performance, making it suitable for solar-blind ultraviolet photodetectors.