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 40nm 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 360nm is close to 59.4%with a UV'/visible rejection ratio more than 4 orders of magnitude.Even at a short waveiength of 280nm,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 be4.96×1014 cm·Hz1/2W-1.