Improving the Photodetector Performance of β-Ga ₂ O ₃ Thin Film by Mg Diffusion

Gallium oxide (Ga2O3) is a solar-blind photodetector material widely used in people’s daily lives and the field of national defense due to its wide and direct band gap, excellent chemical stability, and good thermal conductivity. However, vacancies of Ga and lattice O atoms in the film significantly degrade device performance. Here, high-quality β-Ga2O3 thin films were grown on MgO and Al2O3 substrates by pulsed laser deposition (PLD) method. The microstructure and chemical composition were characterized by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). It was found that Mg in the MgO substrate diffuses into the β-Ga2O3 thin film, while atoms in the Al2O3 substrate do not diffuse. The diffused Mg will suppress the loss of O, which can increase the proportion of lattice O. Photodetector performance measurements reveal that due to the diffusion of Mg, the β-Ga2O3 photodetector grown on MgO substrate has higher photocurrent (6.03 × 10–5 A) and detectivity (1.2 × 1013 Jones) at a response wavelength of 254 nm. Importantly, the responsivity and external quantum efficiency (EQE) of the heteroepitaxial β-Ga2O3/MgO film-based photodetector are as high as 7.94 A/W and 3900% which are more than 25 times higher than the photodetector based on the β-Ga2O3/Al2O3 and are one of the best values of β-Ga2O3 based photodetectors at present. Our findings shed light on applying high-performance solar-blind photodetectors and related optoelectronic devices.