Nitride-based p-i-n photodetectors (PDs) with a p-AlGaN blocking layer were proposed, fabricated, and characterized. It was found that peak responsivities of the PDs with and without a p-AlGaN blocking layer both occurred at 355 nm and with the same value of about 0.076 A/W at zero bias. It was also found that reverse leakage current increased by 7 orders of magnitude after -1000 V electrostatic discharge (ESD) stressing for a conventional homostructure p-i-n PD. In contrast, the heterostructure PD with a 300 nm thick p-Al0.10Ga0.9N blocking layer can endure an extremely large -8000 V ESD surge. (C) 2008 The Electrochemical Society.