Triple-mesa Avalanche Photodiode With Inverted P-Down Structure for Reliability and Stability

A 25-Gbit/s avalanche photodiode (APD) using an inverted p-down structure and triple-mesa structure for eliminating an edge breakdown and reducing an electric field at a surface of the device is proposed and examined. Active area dependence of dark current and activation energy as small as 0.17 eV strongly suggest that the surface leakage current is negligible, and the edge breakdown does not occur. As for RF characteristics, sufficient 3-dB bandwidth of 18 GHz for 25-Gbit/s operation is obtained. We experimentally find that our triple-mesa inverted structure successfully eliminates the possible components which affect the reliability and stability of the APDs.