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 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 similar to 4.96 x 10(14) cm.Hz(1)/W-2(-1).