Method of fabricating a surface coupled InGaAs photodetector

摘要

A photodetector is fabricated in a multilayer structure having a semi-insulating InP substrate (22), an n+ InP contact layer (24) overlying the InP substrate (22), an undoped InGaAs (26) absorbing layer overlying the n+ InP contact layer (24), and a p+ doped InGaAs layer (28) overlying the undoped InGaAs absorbing layer (26). A gold-beryllium p-contact dot (30) is deposited onto the p+ doped InGaAs layer (28) of the multilayer structure. A mesa structure is etched with a citric acid-based etchant into the multilayer structure. The mesa structure includes the metal p-contact dot (30), the p+ doped InGaAs layer (28), and the undoped InGaAs absorbing layer (26). The n+ InP contact layer (24) is patterned, and a passive metallic n-contact layer (32) is deposited onto the patterned n+ InP contact layer (24). A polyimide insulator layer (34) overlying a portion of the structure is deposited and patterned, so that the polyimide insulator layer (34) does not cover the passive metal p-contact dot (30) and the metallic n-contact layer (32). The patterned organic polymer insulator layer (34) is cured and the device is passivated by heating it in a nitrogen atmosphere. Thick metallic gold contact traces are deposited, with one trace (36) extending to the gold-beryllium p-contact dot and the other trace (38) extending to the metallic n-contact layer. <IMAGE>