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 μm with Al mole fraction up to 40% were grown over sapphire substrates. The maximum electron concentration in the layers, as determined by Hall measurements, was as high as ${\text{8×10}}^{17}\hspace{0.5em}{\mathrm{cm}}^{\text{−3}}$ and the Hall mobility was up to 40 ${\mathrm{cm}}^{\mathrm{2}}\mathrm{/Vs}.$ We used this doping technique to demonstrate solar-blind transparent Schottky barrier photodetectors with the cut-off wavelength of 278 nm.