Crystallization of gallium oxynitride thin films

Abstract

Gallium oxynitride (GaON) thin films were RF magnetron sputtered on Si(100) substrates at room temperature under O2 and N2 gas flows with various rates. The films were solid-phase crystallized upon post annealing in a vacuum. The resulting crystalline phases were identified with respect to their anion composition. The optical band gap of GaO1−xNx films scaled linearly with the N2/(N2+O2) flow-rate ratio, from which the nitrogen content (x) was evaluated. At low nitrogen contents (x < 0.3), β-Ga2O(N)3, wherein nitrogen replaced some of the oxygen of β-Ga2O3, crystallized above 500 °C. At intermediate nitrogen contents (0.4 < x < 0.5), γ-Ga3O3N with a cubic spinel structure nucleated above 800 °C, but its crystallinity was rather poor. At high nitrogen contents (x > 0.6), wurzite-GaO1−xNx having a structure correlated with GaN crystallized above 800 °C. Possible reasons are discussed for the amorphous phase being favorable up to high temperatures when the contained amounts of nitrogen and oxygen are comparable.