The thickness effect of p-AlGaN blocking Layer in UV-a bandpass photodetectors

By means of 60-, 150-, and 300-nm-thick blocking p-Al/sub 0.1/Ga/sub 0.9/N 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-Al/sub 0.1/Ga/sub 0.9/N blocking layer, respectively, corresponding to a quantum efficiency of around 46%. Moreover, spectral responsivity for 300-nm-thick blocking p-Al/sub 0.1/Ga/sub 0.9/N 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 × 330 μm² devices given bias of 0 V, the detectivity D/sup */ limited by Johnson noise are calculated to be 3.43 × 10/sup 13/, 6.77 × 10/sup 13/, and 8.22×10/sup 13/ cm/spl middot/Hz/sup 0.5/W/sup -1/, respectively.