Direct mapping and characterization of the surface local field in InGaAs/ InP avalanche photodetectors

In this paper, InGaAs/InP avalanche photodetectors with a variety of guard ring structures are investigated. The electric distribution in the device is characterized by experiment and simulation methods to better understand the dark current mechanisms. It is found that deeper guard rings are more effective in preventing edge break-down for the depressed lateral electric field. Scanning photocurrent microscopy measurement is used to char-acterize the effect of guard ring on InP layer. Our results show that deep guard ring design can reduce the surface electric field. In addition, the 1550 nm response distribution of optimized photodetectors under different operating modes is measured and compared. It shows guard ring can inhibit the edge breakdown. This work demonstrates the significance of guard ring designs of InGaAs/InP avalanche photodetectors, and the charac-terization method will provide an effective way to understand the source of the current generation mechanism.