Nitride-Based MSM photodetectors with a HEMT structure and a low-temperature AlGaN intermediate layer

UV metal-semiconductor-metal (MSM) photodetectors (PDs) based on the AlGaNGaN high-electron-mobility transistor (HEMT) structure with the low-temperature (LT) AlGaN intermediate layer atop were fabricated. A much lower dark current subsequently obtained was in fact benefited by the insertion of the LT AlGaN intermediate layer. In addition, the foregoing structure also rendered PDs with better gate controllability. For the MSM PD structure grown on the LT AlGaN intermediate layer, the resultant responsivity at 360 nm varied from 0.11 to 0.12 AW when the device was biased from 2 to 5 V while the UV/visible rejection was estimated to be around 10³. With a 5 V applied bias, the corresponding noise equivalent power and normalized detectivity (D*) determined were 2.65× 10^-10 W and 1.74× 10⁹ cm Hz0.5 W^-1, respectively.