Progress in α-Ga2O3for practical device applications

Abstract

Recent progress in α-phase gallium oxide (α-Ga2O3) grown on sapphire for low-cost and practical device applications is reviewed. This review focuses on (i) dislocations formed by heteroepitaxy, (ii) p-type conductivity (a common issue with β-Ga2O3), and (iii) thermal instability due to the metastable phase of α-Ga2O3, and discusses efforts aimed at overcoming these issues. The results reveal guidelines for the dislocation density (<1 × 108 cm-2) so that the dislocation scattering is veiled in the electron transport, and for this purpose we mentioned buffer layers and epitaxial lateral overgrowth. Quasi-vertical Schottky barrier diodes (SBDs) show defect-insensitive behavior in current-voltage characteristics under a low current density. We also demonstrate the heterojunction pn diodes with α-phase iridium oxide (α-Ir2O3) or α-(Ir,Ga)2O3 and the ways to improve thermal stability of α-Ga2O3. The up-to-date device characteristics, that is, low on-resistance and large current SBDs, and high reverse voltage of 1400 V of a pn junction suggest promising development in α-Ga2O3-based devices.