Schottky Barrier Ultraviolet Photodetectors on Epitaxial Lateral Overgrown GaN

Schottky barrier photovoltaic detectors have been fabricated on epitaxial lateral overgrown GaN layers. The devices show a responsivity of 130 mA/W, independent of optical power and diode size. Due to the lower defect concentration, an improvement of one order of magnitude in the visible rejection ratio has been observed, in comparison with Schottky barrier detectors on standard GaN layers on sapphire. The device time response is RC limited, and the low capacitance of these devices results in an increased bandwidth (<30 MHz in devices with a diameter of 200 μm). A lower noise equivalent power is also observed, due to the reduced leakage current. Detectivities of 5 × 109 Hz1/2 mW—1 were obtained in devices with a diameter of 400 μm, working at —3.4 V bias.