Editors' Choice—Electrical Properties and Deep Traps in α-Ga2O3:Sn Films Grown on Sapphire by Halide Vapor Phase Epitaxy

Films of α-Ga2O3 doped with Sn were grown by halide vapor phase epitaxy (HVPE) on planar and patterned sapphire substrates. For planar substrates, with the same high Sn flow, the total concentration of donors was varying from 1017 cm−3 to high 1018 cm−3. The donor centers were shallow states with activation energies 35–60 meV, centers with levels near Ec–(0.1–0.14) eV (E1), and centers with levels near Ec–(0.35–0.4) eV (E2). Deeper electron traps with levels near Ec−0.6 eV (A), near Ec−0.8 eV (B), Ec−1 eV (C) were detected in capacitance or current transient spectroscopy measurements. Annealing of heavily compensated films in molecular hydrogen flow at 500 °C for 0.5 h strongly increased the concentration of the E1 states and increased the density of the E2 and A traps. For films grown on patterned substrates the growth started by the formation of the orthorhombic α-phase in the valleys of the sapphire pattern that was overgrown by the regions of laterally propagating α-phase. No improvement of the crystalline quality of the layers when using patterned substrates was detected. The electric properties, the deep traps spectra, and the effects of hydrogen treatment were similar to the case of planar samples.