High-photosensitivity AlGaN-based UV heterostructure-field-effect-transistor-type photosensors

Abstract We report the development of high-performance AlGaN/AlN heterostructure-field-effect-transistor-type (HFET) photosensors with a p-type GaN optical gate and detection wavelengths that are restricted to 220–280 nm. These photosensors employ a two-dimensional electron gas induced at the hetero-interface between Al 0.6 Ga 0.4 N and Al 0.5 Ga 0.5 N as a highly conductive channel. In addition, a p-type GaN optical gate is employed to deplete a channel. Consequently, we obtained a high photosensitivity of over 4 × 10 3 A/W and an externally low dark current density of approximately 5 × 10 −10 A/mm at a source–drain voltage of 3 V. We also determined that the detection range of light wavelength in these HFET photosensors can be controlled by controlling the AlN molar fraction in the AlGaN channel layer. The results are very promising for the development of completely solar-blind high-performance photosensors with high photosensitivity.