The thickness effect of p-AlGaN blocking layer in UV-A bandpass photodetectors

By means of 60-, 150-, and 300-nm-thick blocking p-Al0.1Ga0.9N layers, we have successfully achieved high performance on nitride-based p-i-n bandpass photodetectors. The peak responsivities were estimated to be 0.131, 0.129, and 0.13 A/W at 354, 357, and 356 nm for 60-, 150-, and 300-nm-thick p-Al0.1Ga0.9N blocking layer, respectively, corresponding to a quantum efficiency of around 46%. Moreover, spectral responsivity for 300-nm-thick blocking p-Al0.1Ga0.9N layer shows the narrowest bandpass characteristics from 320 to 365 nm (UV-A region). The photodetectors exhibit a 20-V break-down voltage and a small dark current of around 3 pA at 5-V reverse bias. For our 330 x 330 mu m(2) devices given bias of 0 V, the detectivity D* limited by Johnson noise are calculated to be 3.43 x 10(13), 6.77 x 10(13), and 8.22 x 10(13) cm (.) Hz(0.5)W(-1), respectively.