Indium-silicon co-doping of high-aluminum-content AlGaN for solar blind photodetectors

We report on an indium-silicon co-doping approach for high-Al-content AlGaN layers. Using this approach, very smooth crack-free n-type AlGaN films as thick as 0.5 mum with Al mole fraction up to 40% were grown over sapphire s ubstrates. The maximum electron concentration in the layers, as determined by Hall measurements, was as high as 8x10(17) cm(-3) and the Hall mobility was up to 40 cm(2)/Vs. We used this doping technique to demonstrate solar-b lind transparent Schottky barrier photodetectors with the cut-off wavelengt h of 278 nm. (C) 2001 American Institute of Physics.