Realisation of ‘Solar Blind’ AlGaN Photodetectors: Measured and calculated spectral response

AlxGa1−xN solar blind photoconductors are fabricated and characterized. The cutoff wavelength of these detectors is as low as 275 and 271 nm with aluminium fraction of 49.6 and 54.1%, respectively. The used AlGaN active layers were grown on (0001) sapphire substrates by low pressure metalorganic chemical vapour deposition (LP-MOCVD). The full width at half maximum (FWHM) of X-ray rocking curve from (0002) diffraction indicates the good quality of these samples. Optical properties are investigated with photoluminescence and absorption measurements. The variation of the spectral response with applied voltage and modulation frequency is investigated. Better results are obtained with 12 Hz and 20 V. Compared to other researches, a high rejection ratio is obtained. The simulation of the photoresponse using the voltage dependent responsivity allows the determination of the carrier lifetime. We obtained a value of 0.15 and 0.13 ms for x=0.49 and 0.54, respectively.