Wang Guosheng

GaN ultraviolet p–i–n photodetectors with enhanced deep ultraviolet quantum efficiency

GaN ultraviolet (UV) p–i–n photodetectors (PDs) with a thin p-AlGaN/GaN contact layer are designed and fabricated. The PD exhibits a low dark current density of∼7 nA/cm2 under −5 V, and a zero-bias peak responsivity of ∼0.16 A/W at 360 nm, which corresponds to a maximum quantum efficiency of 55%. It is found that, in the wavelength range between 250 and 365 nm, the PD with thin p-AlGaN/GaN contact layer exhibits enhanced quantum efficiency especially in a deep-UV wavelength range, than that of the control PD with conventional thin p-GaN contact layer. The improved quantum efficiency of the PD with thin p-AlGaN/GaN contact layer in the deep-UV wavelength range is mainly attributed to minority carrier reflecting properties of thin p-AlGaN/GaN heterojunction which could reduce the surface recombination loss of photon-generated carriers and improve light current collection efficiency.