AlGaN solar-blind photodetectors grown by low pressure MOCVD

Abstract

Al_xGa_1−xN ternary alloys are very attractive materials for application to ultraviolet (UV) photodetection. In this work, high Al content Al_xGa_1−xN films are grown on sapphire substrate by low pressure metalorganic chemical vapor deposition (MOCVD). The Al content in the Al_xGa_1−xN epilayer is estimated to be 54% by high resolution X-ray diffraction (HRXRD) and Vegard’s law. The full width at half maximum (FWHM) of the rocking curve for the Al_0.54Ga_0.46N (0002) is about 597 arcsec. According to the transmittance measurement result, our sample is suitable for fabricating solar-blind photodetectors. The observed Fabry-Perot fringes in the transmission region indicate that high optical quality is obtained. Solar-blind metal-semiconductor-metal (MSM) photodetectors based on the MOCVD-grown Al_0.54Ga_0.46N film are fabricated and tested. The detector has a low dark current of about 31?pA under a bias voltage of 5?V. An UV/visible contrast of about four orders of magnitude is observed and responsivity increases with increments of the bias voltage.