Microstructure Evolution and Electrical Behaviors for High-Performance CuO/Zr-Doped β-GaO Heterojunction Diodes.

Beta-gallium oxide (β-GaO) is emerging as a promising ultrawide band gap (UWBG) semiconductor, which is vital for high-power, high-frequency electronics and deep-UV optoelectronics. It is especially significant for flexible wearable electronics, enabling the fabrication of high-performance GaO-based devices at low temperatures. However, the limited crystallinity and pronounced structural defects arising from the low-temperature deposition of GaO films significantly restrict the heterojunction interface quality and the relevant electrical performance of GaO-based devices. In this work, cuprous oxide (CuO)/Zr-doped β-GaO heterojunction diodes are fabricated by magnetron sputtering without intentional substrate heating, followed by an investigation into their microstructure and electrical behaviors. Zr doping can markedly enhance the GaO crystallinity at low substrate temperatures, transforming the amorphous structure of pristine GaO films into the crystallized β phase. Moreover, crystalline β-GaO facilitates the epitaxial growth of the CuO phase, suppressing the formation of detrimental secondary phase CuO at the heterojunction interface. Benefiting from the high-quality heterojunction interface, the CuO/Zr-doped β-GaO heterojunction diode exhibits a near-ideal electrical behavior with a low ideality factor of 1.6. The consistent electrical parameters extracted from current-voltage () and capacitance-voltage () measurements also confirm the high quality of β-GaO. This work highlights the potential for the low-temperature production of high-quality β-GaO-based heterojunction devices through Zr doping.