High UV/visible contrast photodiodes based on epitaxiallateral overgrown GaN layers

Schottky photodiodes have been fabricated on epitaxial lateral overgrown GaN layers, showing a responsivity of 130 mA/W. An improvement of one order of magnitude in the UV/visible contrast has been observed, in comparison with devices on standard GaN on sapphire. The significantly lower residual doping concentration reduces markedly the leakage current, and increases the detector bandwidth (> 30 MHz in devices with a diameter phis = 200 µm). Detectivities as high as 5 × 109 Hz1/2mW–1 were obtained in photodiodes with phis = 400 µm, working at –3.4 V bias.