High Deep-Ultraviolet Quantum Efficiency GaN P–I–N Photodetectors with Thin P-GaN Contact Layer

GaN ultraviolet(UV)p-i-n photodetectors(PDs)with a 40 nm thin p-GaN contact layer are fabricated on sapphire substrates,which exhibit enhanced quantum efficiency especially in a deep-UV wavelength range.The PDs show good rectification behavior and low dark current in pA level for reverse bias up to-10 V.Under zero bias,the maximum quantum efficiency of the PD at 360 nm is close to 59.4%with a UV/visible rejection ratio more than 4 orders of magnitude.Even at a short wavelength of 280 nm,the quantum efficiency of the PD is still around 47.5%,which is considerably higher than that of a control device with a thicker p-GaN contact layer.The room temperature thermal noise limited detectivity of the PD is calculated to be~4.96×10^(14) cm·Hz^(1/2)W^(-1).