Assessment of Trapping Phenomena in As-Grown and Thermally-Treated Si-Doped κ-Ga2O3 Layers via Optical Admittance Spectroscopy

The impact of thermal treatments on the trapping phenomena in (001) Si-doped κ-Ga2O3 epi-layers, via optical admittance spectroscopy technique, is reported. Two Pt/κ-Ga2O3 Schottky contacts are investigated: one made on top of an as-grown Si-doped κ-Ga2O3 layer and the other on a thermally treated one. Three different illumination conditions, including monochromatic UV-C (λ = 254 nm), UV-B (λ = 312 nm), and UV-A (λ = 365 nm), are employed for the capacitance–voltage (C–V) measurements at different bias and AC frequencies to investigate traps and deep levels in κ-Ga2O3:Si. The net donor density profiles in dark and approximate density of photoionized traps of the as-grown and thermally treated samples are extracted from the C–V curves in the dual-frequency mode under different illumination conditions. A SnO/κ-Ga2O3 p-n heterojunction, where the κ-Ga2O3:Si layer underwent a double thermal treatment, is also investigated to better understand the relation between thermal treatment and distribution of trap density. The transient photocapacitance and photocurrent measurements are performed under the same illumination conditions to evaluate the response times of traps. This study provides a better understanding of the trapping phenomena in the as-grown and thermally treated κ-Ga2O3:Si epi-layers, which are important for UV-C detection applications.