Quasi-vertical ε-Ga2O3 solar-blind photodetectors grown on p-Si substrates with Al2O3 buffer layer by metalorganic chemical vapor deposition

(002)-oriented ε-Ga2O3 thin films were heteroepitaxially grown on p-Si (111) substrates by metalorganic chemical vapor deposition (MOCVD). The introduction of Al2O3 buffer layer significantly improved the crystallinity and surface morphology of the ε-Ga2O3 films. Quasi-vertical deep ultraviolet photodetectors (UV-PDs) were fabricated and characterized based on ε-Ga2O3 films grown with and without the Al2O3 buffer layer. Compared with the n-Ga2O3/p-Si device, the n-Ga2O3/Al2O3/p-Si UV-PDs showed enhanced device performance under 254 nm illumination, including an ultralow dark current of 99.4 pA, a photo-to-dark current ratio of 104, a high ultraviolet responsivity of 8.1 A/W at −10 V, and a fast photo response with rise/decay time of 0.89 s/0.29 s. The improved device performance can be ascribed to the energy band engineering of n-Ga2O3/Al2O3/p-Si heterojunction. The Al2O3 layer works not only as a buffer layer but also as an electron-blocking layer, which allows holes to cross the heterojunction under the reverse bias. This work shows a promising method to develop high-performance ε-Ga2O3 UV-PDs on cost-effective Si substrates.