Solar-blind MSM-photodetectors based on AlxGa1−xN/GaN heterostructures grown by MOCVD

Solar-blind MSM-photodetectors based on the AlGaN/GaN heterostructutes grown by MOCVD technology were fabricated and investigated. Directly on the MSM-diode we have measured a Schottky barrier height of 1.1 eV for Ni and 1.4 eV for Mo contacts on AlGaN. Effect of different buffer layers on the detector performances has been demonstrated. Detectors exhibit low dark currents and high sensitivity within the range of 250–290 nm. High-speed response of MSM-detectors is analyzed. Effect of optical excitation level on detector performance is discussed. At low excitation level the detector speed of response is limited by parasitic capacitance of interdigitated diode structure and by the transit time of the photogenerated carriers. At high excitation level the detector speed of response is limited by the field screening caused by the space-charge of the holes. The impulse response of AlGaN/GaN MSM-detector is compared favorably with GaAs MSM-device.