Modelling AlGaN heterojunction solar-blind photodetectors

There is considerable interest in the detection of UV radiation in the Hartley Ozone band (200-300 nm). Solar radiation in this range of wavelengths is strongly absorbed by stratospheric ozone producing a "black" background at the Earth's surface. Consequently, terrestrial UV sources such as fires, furnaces and missile plumes can be detected with a large signal-to-background ratio and, therefore, a low probability of false alarm, Photodetectors operating in these wavelengths are known as solar-blind detectors. The AlGaN material system has a direct bandgap that can be tailored to this range of UV wavelengths by varying the proportion of the Al and Ga in the alloy, Recent work on the analytical modelling of UV photodetectors in the AlGaN material system has suggested designs for p-i-n diodes that should prove of use in solar-blind-detection applications. In this conference paper, we extend our earlier modelling work by utilizing the numerical device simulator, MEDICI, in conjunction with an AlGaN material library that has been developed at UWA. This powerful combination is used here to investigate the effect of band offsets on the responsivity of heterojunction p-i-n photodetectors operating in the 200-400 nm regime.