Origin of near-failure in Au contacts to polycrystalline β-Ga2O3 at high temperatures using interfacial studies

Abstract

Suitable contacts to gallium oxide are a controversial topic with contact behavior depending heavily on the pre- and post-processing conditions. Especially for the extreme environment applications such as those involving high temperatures, contact chemistry is varied and severely lacks understanding. Herein, we report on conventional pure Au contacts to polycrystalline β-Ga2O3, used as Schottky contacts, and explore the origin of their near-failure at high temperature up to 850 °C. For this purpose, β-Ga2O3 with Au interdigitated electrodes is subjected to high temperature annealing and their interface chemistry is studied and correlated with device performance for solar-blind photodetection. Around the optimized temperature of 450 °C, the performance of the PDs is found to be maximum, whereas it reduces drastically at 850 °C. Physical damage to the electrodes along with the formation of intermetallic gold-gallium alloy is observed via XPS depth profile studies and found to be the reason for the near-failure of device at extreme conditions. Although the alloy formation begins to slightly appear at 650 °C and reduces the performance, still it does not lead to device breakdown. This study proves that unlike its counterparts GaN and GaAs, which have reported alloy formation at lower temperatures, β-Ga2O3 shows a higher resilience to the formation of Au–Ga alloy and can withstand higher temperatures before the actual device failure is reached. The proposed study shows the stability of standard metal contacts to Ga2O3 based devices, which have far-reaching implications for the future commercialization of wideband gap semiconductor based (opto)electronics.