Avalanche photodiode and method of making the same

摘要

A mesa-structure avalanche photodiode in which a buffer region (130) in the surface of the mesa structure (120) effectively eliminates the sharply-angled, heavily doped part of the cap layer (110) that existed adjacent the lightly-doped n-type multiplication layer (108) and p-type guard ring (140) before the buffer region was formed. This reduces the electric field strength at the ends of the planar epitaxial P-N junction (114) and prevents edge breakdown in this junction. The lateral extent of the guard ring is defined by a window (162) formed in a masking layer (164) prior to regrowth of the guard ring. This guard ring structure eliminates the need to perform additional processing steps to define the lateral extent of the guard ring and to passivate the periphery of the guard ring.