Growth, fabrication, and characterization of III-nitride semiconductors for high-performance ultraviolet avalanche photodiodes by metalorganic chemical vapor deposition
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The objective of the proposed research is to develop high-performance III-nitride-based ultraviolet (UV) avalanche photodiodes (APDs) with high optical gain and low leakage current using metalorganic chemical vapor deposition (MOCVD) system. However, the realization of high-performance UV-APDs has been hampered by high dislocation densities originating from heteroepitaxial layer grown on the lattice- and thermal-mismatched substrates, resulting in higher dark current density, device size limitation, and device failure by microplasma formation as well as low yield and non-uniformity in an array format. To achieve high-performance UV-APDs and arrays, material growth on bulk GaN substrates with low dislocation density, sophisticated device fabrication process including low-damage etching and high-quality dielectric passivation, and new UV-APD structure by employing impact-ionization engineering were discussed in this research. The major aims of the research are as follows: 1) to improve characteristics of 5% AlGaN p-i-n UV-APDs 2) to demonstrate uniform and reliable GaN p-i-n UV-APD arrays with large detection area 3) to demonstrate GaN p-i-p-i-n separate absorption and multiplication (SAM) UV-APDs.