High photosensitivity AlGaN/GaInN/GaN heterojunction field-effect transistor type visible photosensors

Abstract

We realized the high-performance AlGaN/GaInN/GaN-based heterostructure field-effect transistor type visible photosensors with high photosensitivity and high rejection ratio. We designed the photosensors including two-dimentional electron gas layer at AlGaN/GaInN/GaN hetero-interface to detect visible light with high photosensitivity. Also, carrier depletion using p-type GaN gate was applied for reduction of the dark current. Furthermore, we realized photosensor with externally low dark current density by applying a C-doped GaN layer as an underlying layer. We found that inserting an unintentionally doped GaN interlayer between the GaInN active layer and the C-doped GaN underlying layer is important for realizing a high-performance photosensors. By employing these device designs, a high photosensitivity of 104 A W−1 at wavelength of 430 nm and high rejection ratio of more than 106 were realized under the irradiation of 100 μW cm−2. The absorption edge wavelength was approximately 480 nm corresponding to the bandgap energy of GaInN active layer. Therefore, this device structure is useful as the visible photosensor with high sensitivity and high rejection ratio.