High-sensitivity β-Ga_2O_3 solar-blind photodetector on high-temperature pretreated c-plane sapphire substrate

Abstract

Recently, monoclinic Ga2O3 (β-Ga2O3) photodetectors (PDs) have been extensively studied for various commercial and military applications due to the merits of intrinsic solar rejection, high gain, and great compactness. In this work, c-plane sapphire substrates were annealed under different temperatures in a vacuum furnace prior to the molecular beam epitaxy (MBE) of β-Ga2O3 thin film, which yielded a smoother surface and even a terrace-and-step-like morphology on the substrate, resulting in improved crystallinity of the epitaxial film. Accordingly, both the dark and photo currents of β-Ga2O3 metal-semiconductor-metal (MSM) PDs were increased by the enhanced carrier mobility (μ) of the more crystalline film. However, the substrate-annealing temperature must be sufficiently high to offset the rise of the dark current and thus achieve a remarkable improvement in the photodetection properties. As a result, the PD fabricated on the 1050 °C-annealed substrate exhibited extremely high sensitivity, for example, high responsivity (R) of 54.9 A/W and large specific detectivity (D*) of 3.71 × 1014 Jones. Both parameters were increased by one order of magnitude because of the combined effects of the dramatic increase in μ and the effective reduction in defect-related recombination centers. Nevertheless, the latter also prolonged the recovery time of the PD. These findings suggest another way to develop β-Ga2O3 PD with extremely high sensitivity.