Metal-Semiconductor-Metal Ultraviolet Photodiodes Fabricated on Bulk GaN Substrate

Abstract

We report the demonstration of a GaN-based planar metal-semiconductor-metal (MSM) ultraviolet photodetector (PD). The MSM PD with semitransparent interdigitated Schottky electrodes is fabricated on low-defect-density GaN homoepitaxial layer grown on bulk GaN substrate by metal-organic chemical vapor deposition. The dislocation density of the GaN homo-epilayer characterized by cathodoluminescence mapping technique is ~5×106 cm−2. The PD exhibits a low dark current density of ~4.1×10−10 A/cm2 and a high UV-to-visible rejection ratio up to 5 orders of magnitude at room temperature under 10 V bias. Even at a high temperature of 425 K, the dark current of the PD at 10 V is still <1×10−9 A/cm2 with a reasonable UV-to-visible rejection ratio more than 3×104, indicating that such kind of PDs are suitable for high temperature operation.