High responsivity β-Ga₂O₃ Schottky photodiodes on off-axis sapphire substrate

In this work, Schottky photodiodes (SPDs) were fabricated using β-Ga₂O₃ films, which were heteroepitaxially grown on sapphire substrates by low-pressure chemical vapor deposition. Importantly, the sapphire substrates possess a 6° off-axis angle from c-plane towards m-plane, which contributes to a high crystallinity of the β-Ga₂O₃ films with a full width at half maximum (FWHM) of 0.55° in XRD spectrum accompanied with higher photoresponse compared with the counterpart film on a normal c-plane sapphire without off-axis. Moreover, the performances of the SPDs, such as responsivity, external quantum efficiency, and specific detectivity, can be improved by reducing the electrode spacing distance at appropriate length, which should result from the weakened scattering and recombination within a smaller active area. Accordingly, responsivities of 385 A/W and 3210 A/W at the reverse and forward bias (-20/20 V) are obtained in the SPD device with a 10 μm electrode spacing. Moreover, this device also presents a high external quantum efficiency of 1.88 × 10⁵%, a specific detectivity of 1.3 × 10¹² Jones, and a high rejection ratio of 7.7 × 10³, respectively. Finally, a solar-blind ultraviolet communication system was set up based on the fabricated high-performance SPD, which can successfully transfer the message via the encoded optical signals. This work demonstrates the potential application in solar-blind ultraviolet photodetection and communication by Ga₂O₃-based SPDs.