High gain and high ultraviolet/visible rejection ratio photodetectors using p-GaN/AlGaN/GaN heterostructures grown on Si
Qifeng Lyu, Huaxing Jiang, Kei May Lau
Abstract
We report high performance ultraviolet (UV) photodetectors (PDs) based on p-GaN-gated AlGaN/GaN heterostructures grown on silicon substrates. Benefitting from the high electrical gain resulting from the transistor-like operation of the device, a photocurrent as high as 4.8 mA/mm was achieved with UV illumination. Due to the effective depletion of the two-dimensional electron gas at the AlGaN/GaN heterointerface via a p-GaN optical gate, the dark current was suppressed to below 3 × 10−8 mA/mm. A high photo-to-dark current ratio over 108 and a high responsivity of 2 × 104 A/W were demonstrated in the device. Moreover, with a cutoff wavelength of 395 nm, the PDs exhibited an ultrahigh UV-to-visible rejection ratio of over 107. Limited by a persistent photoconductivity effect, the rise time and fall time of the device frequency response were measured to be 12.2 ms and 8.9 ms, respectively. The results suggest the potential of the proposed PDs for high-sensitivity UV detection.