Uniform and High Gain GaN p-i-n Ultraviolet APDs Enabled by Beveled-Mesa Edge Termination

In this letter, a beveled-mesa edge termination technology was developed to improve the performance of GaN pi-n ultraviolet avalanche photodiodes (APDs). Simulation results showed that the beveled-mesa is effective in reduction of the electric field at the mesa sidewall. With a photoresist thermal-reflow process, 12°-angle beveled-mesa APDs were fabricated from homoepitaxial p-i-n structures on GaN substrate. The most beneficial property of the beveled-mesa termination is the uniform breakdown-characteristic of the beveled-mesa APDs compared to the vertical-mesa APDs. Record-high VBR uniformity of 95.4 V ± 0.2 V and average avalanche gain up to 3 × 10
⁶
were observed for the beveled-mesa APDs within a linear array across 4 mm side-length. These results indicate the potential of the beveledmesa GaN APD array for ultraviolet light imaging applications.