Enhancing Thin-Film Properties of Hetero-Epitaxial α-Ga₂O₃ for Scalable UV Photodetectors

This study investigates the performance of ultra-thin α-Ga₂O₃-based metal-semiconductor-metal (MSM) photodetectors. The device features an unintentionally doped α-Ga₂O₃ active layer grown on a sapphire substrate, patterned Ti/Au electrodes, and an SiO₂ passivation layer. We present a cost-effective process for fabricating ultraviolet (UV) photodetectors.
Hydride vapor phase epitaxy (HVPE) was employed to grow the α-Ga₂O₃ layers, offering high efficiency with rapid growth rates, large-area scalability, and cost-effectiveness. This method produces high-quality, uniform crystalline layers, making it ideal for power electronics and UV photonic devices. Unlike the costly homo-epitaxial growth on Ga₂O₃ substrates, the α-Ga₂O₃ active layer was hetero-epitaxially grown on sapphire substrates, demonstrating strong UV C-band absorption (>80%) even with a thin layer.
However, hetero-epitaxial growth can introduce internal and interfacial defects that may impair device performance. To mitigate these issues, a rapid thermal annealing (RTA) process in an oxygen atmosphere was applied. Increased RTA durations significantly enhanced device performance, achieving faster response times and higher responsivity, even with an active layer thickness of just 200 nm.
These findings demonstrate the potential for cost-effective and scalable production of thin α-Ga₂O₃-based UV devices. Furthermore, the RTA process effectively improves thin-film properties, broadening the applicability of heterojunction α-Ga₂O₃ devices for ultraviolet photodetection and other optoelectronic applications.