High gain and high ultraviolet/visible rejection ratio photodetectors using p-GaN/AlGaN/GaN heterostructures grown on Si

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 4.8mA/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 3x10(-8) mA/mm. A high photo-to-dark current ratio over 10(8) and a high responsivity of 2x10(4) A/W were demonstrated in the device. Moreover, with a cutoff wavelength of 395nm, the PDs exhibited an ultrahigh UV-to-visible rejection ratio of over 10(7). 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. Published under license by AIP Publishing.