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

Abstract

Films of α -Ga 2 O 3 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 10 17 cm −3 to high 10 18 cm −3 . The donor centers were shallow states with activation energies 35–60 meV, centers with levels near E c –(0.1–0.14) eV (E1), and centers with levels near E c –(0.35–0.4) eV (E2). Deeper electron traps with levels near E c −0.6 eV (A), near E c −0.8 eV (B), E c −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.