Effects of Hydrogen Plasma Treatment Condition on Electrical Properties of beta-Ga2O3

Abstract

The effects of hydrogen or deuterium plasma treatment at 330 degrees C on electrical properties and deep trap spectra of n-type beta-Ga2O3 films grown by halide vapor phase epitaxy on native n(+) substrates are reported. Under plasma treatment conditions giving rise to higher energy ions (280 eV), hydrogen penetrates into the HVPE films and fully compensates or passivates shallow donors to similar to 2 mu m from the surface. The Fermi level in this high-resistivity layer is pinned by electron traps near E-c-1 eV (E3 traps) also present in the starting material. Annealing at 450 degrees C shifts the pinning position to another dominant deep trap in the starting material, the E2* traps near E-c-0.75 eV. Subsequent annealing at 550 degrees C almost fully restores the electrical properties. By sharp contrast, plasma treatment under conditions of low energy ions (35eV) severely reduced hydrogen incorporation and only slightly increased the near-surface donor concentration. The observed differences are discussed under the assumption that hydrogen is introduced in the form of isolated acceptor interstitials with the charge transfer level near E-c-0.5 eV in the first case, but as a donor with level inside the conduction band in the second case as proposed by recent theoretical calculations. (C) 2019 The Electrochemical Society.