Back illuminated AlGaN solar-blind photodetectors

We report the growth, fabrication, and characterization of AlxGa1-xN (0 less than or equal to x less than or equal to 0.60) heteroepitaxial back-illuminated solar-blind p-i-n photodiodes on (0001) sapphire substrates. The group III-nitride heteroepitaxial layers are grown by low-pressure metalorganic chemical vapor deposition on double polished sapphire substrates using various growth conditions. The back-illuminated devices exhibit very low dark current densities. Furthermore, they exhibit external quantum efficiencies up to 35% at the peak of the photoresponse (lambda similar to 280 nm). Improvements were made to the growth technique in order to achieve crack-free Al0.4Ga0.6N active regions on a thick Al0.6Ga0.4N window layer and to obtain activated p-type Al0.4Ga0.6N layers. (C) 2000 American Institute of Physics. [S0003-6951(00)05438-3].