Solar-blind photodetectors prepared using semi-insulating Co:β-Ga2O3 single crystals that are stable over a wide temperature range

Abstract

Semi-insulating (SI) β-Ga₂O₃ provides an ultrahigh resistivity that is stable over a wide temperature range which is required in challenging temperature environments, such as in fire prewarning, atmospheric monitoring, and space exploration. A promising deep-level acceptor of Co, which has a more suitable energy location than is found in conventional acceptors (Fe, Mg, etc.), is introduced into the band structure of β-Ga₂O₃, which might suppress the deterioration of the SI effect and realize the availability of β-Ga₂O₃ single crystals with stable resistivity in harsh temperature applications. The Co-doped β-Ga₂O₃ (Co:β-Ga₂O₃) single crystal possesses a high transmittance and a low free-electron concentration. A stable temperature-dependent resistivity plateau of Co:β-Ga₂O₃ (which is maintained at 10¹¹ Ω cm from room temperature (RT) to 300 °C) is found for the first time, and the thermal activation energy is fitted to be 2.1 eV, which is closer to the center of the bandgap than that of Fe and Mg. Hence, the dark currents of photodetectors based on the Co:β-Ga₂O₃ substrate are effectively suppressed, and the photoresponse performances vary subtly from RT to 260 °C. This work shows the ultrahigh resistivity stability and the excellent SI effect of Co:β-Ga₂O₃ over a wide temperature range, indicating its application prospects in extreme environments and providing more possibilities for the thermal design of β-Ga₂O₃ devices.