High gain Ga2O3/GaN avalanche photodetector with separated absorption and multiplication structure

The β-Ga2O3/p-GaN heterojunction avalanche photodetector (APD) with separated absorption and multiplication (SAM) structure was fabricated by metal–organic chemical vapor deposition. Through x-ray diffraction and scanning electron microscopy characterization, the Ga2O3 films exhibit relatively high crystalline quality. Through reasonable design of the electron concentration and thickness of the Ga2O3 layers, the device achieves an ultrahigh avalanche gain (Gain) of 1.75 × 107, an external quantum efficiency (EQE) of 4.53 × 107%, and a high responsivity (R) of 9.28 × 104 A/W under 254 nm solar-blind ultraviolet illumination (5 μW/cm2). The working mechanism of SAM-APD was further validated through TCAD simulations. Compared to conventional APDs, the SAM structure can significantly enhance avalanche gain and EQE, thereby improving the weak signal detection level of the APD effectively.