AlGaN ultraviolet photodetectors grown by molecular beam epitaxy on Si(111) substrates

The performance of AlGaN metal–semiconductor–metal (MSM) photodetectors grown on Si(111) is presented in this article. It is shown that the growth of an adequate AlN buffer layer is critical to achieve visible-blind devices, and that its role as an effective electrical insulator of the conductive substrate was found to be more efficient for N-excess AlN growth. The increase of Al content produced a transition from photoconductor to MSM photodiode behaviour, as determined from the detector responsivity, temporal response, and UV/visible contrast. The effect of the contact metal on photoconductive gain and UV/visible contrast was also studied.