Lian, Hai-FengWang, Guo-ShengLu, HaiRen, Fang-FangChen, DunjunZhang, R.Zheng, Youdou2015-12-100256-307Xhttp://hdl.handle.net/1885/62280GaN 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·Hz1/2 W-1.201310.1088/0256-307X/30/1/0173022015-12-10