Microstructure Evolution and Electrical Behaviors for High-Performance Cu 2 O/Zr-Doped β-Ga 2 O 3 Heterojunction Diodes.

Beta-gallium oxide (β-Ga ₂ O ₃ ) 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 Ga ₂ O ₃ -based devices at low temperatures. However, the limited crystallinity and pronounced structural defects arising from the low-temperature deposition of Ga ₂ O ₃ films significantly restrict the heterojunction interface quality and the relevant electrical performance of Ga ₂ O ₃ -based devices. In this work, cuprous oxide (Cu ₂ O)/Zr-doped β-Ga ₂ O ₃ 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 Ga ₂ O ₃ crystallinity at low substrate temperatures, transforming the amorphous structure of pristine Ga ₂ O ₃ films into the crystallized β phase. Moreover, crystalline β-Ga ₂ O ₃ facilitates the epitaxial growth of the Cu ₂ O phase, suppressing the formation of detrimental secondary phase CuO at the heterojunction interface. Benefiting from the high-quality heterojunction interface, the Cu ₂ O/Zr-doped β-Ga ₂ O ₃ heterojunction diode exhibits a near-ideal electrical behavior with a low ideality factor of 1.6. The consistent electrical parameters extracted from current-voltage ( J-V ) and capacitance-voltage ( C-V ) measurements also confirm the high quality of β-Ga ₂ O ₃ . This work highlights the potential for the low-temperature production of high-quality β-Ga ₂ O ₃ -based heterojunction devices through Zr doping.