High-Responsivity Solar-Blind Photodetectors Formed by Ga<sub>2</sub>O<sub>3</sub>/p-GaN Bipolar Heterojunctions
Ping-Feng Chi, Feng-Wu Lin, Ming-Lun Lee, Jinn‐Kong Sheu
Abstract
In this article, solar-blind photodetectors (PDs) composed of Ga2O3/p-GaN bipolar heterojunctions formed through thermal oxidation and silicon ion implantation processes based on p-GaN epitaxial films are demonstrated. X-ray diffraction and electrical analyses indicate that an oxygen-ambient oxidation process converts the p-GaN into semi-insulating (2̅01) β-Ga2O3 films. The β-Ga2O3 films are implanted with silicon ions to transform their insulating properties into n-type β-Ga2O3 with low resistivity and an electron concentration of up to 1.5 × 1019/cm3. These Si-implanted β-Ga2O3 films exhibit electron mobilities of approximately 300 and 150 cm2 v–1 s–1, measured at temperatures of 150 and 300 K, respectively. Ohmic contacts using Ti/Al bi-layer metal deposited on the Si-implanted β-Ga2O3 films exhibit an acceptable low contact resistance for fabricating n-Ga2O3/i-Ga2O3/p-GaN heterojunction PDs. The PDs exhibit high photoresponses in the solar-blind band with a cut-off wavelength of 250 nm. The preliminary results suggest that device-grade β-Ga2O3 films can be achieved through thermal oxidation of GaN films.