Crystal-phase engineering of ε-Ga2O3 for high-performance deep UV photodetectors via MOCVD

Abstract

Gallium oxide (Ga₂O₃), with an ultrawide bandgap corresponding to the deep ultraviolet (DUV) spectra range, provides a potential subversive scheme for the filter-free DUV photodetection. Meanwhile, the various crystal phases of Ga₂O₃ provide more substrate options for achieving heteroepitaxy, with the coupling of Ga₂O₃ to SiC substrates conducive to developing integrated Ga₂O₃ DUV photodetectors. Phase engineering of β-Ga₂O₃ and ε-Ga₂O₃ was achieved on the commercial 4H-SiC substrate via metal-organic chemical vapor deposition. According to the in-depth analysis of different Ga₂O₃ growth stages, it was found that β-Ga₂O₃ is easy to form under high-pressure growth conditions, while low-pressure conditions promote the formation of ε-Ga₂O₃ at 500°C. Furthermore, the developed ε-phase dominated Ga₂O₃ DUV photodetector exhibits obvious advantages in high responsivity (∼639 A/W), photo-to-dark current ratio (∼2.4×10⁷), external quantum efficiency (∼3.15×10⁵%), and specific detectivity (∼9.62×10¹³ Jones) under 254 nm illumination. This work not only reveals the growth mechanism of Ga₂O₃ films under various pressures but also ensures the great potential of ε-Ga₂O₃ for highly sensitive DUV detection on the heterogeneous substrate, which is expected to expand the application of Ga₂O₃ optoelectronic devices.