Al x Ga1-x N solar-blind photodetectors grown by low pressure MOCVD

Abstract

Al x Ga1-x N ternary alloys are very attractive materials for application to ultraviolet (UV) photodetection. In this work, high Al content Al x Ga1-x N films are grown on sapphire substrate by low pressure metalorganic chemical vapor deposition (MOCVD). The Al content in the Al x Ga1-x N 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 Al0.54Ga0.46N (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. Solarblind metal-semiconductor-metal (MSM) photodetectors based on the MOCVD-grown Al0.54Ga0.46N 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.