Mesa-Type Photodetectors With Lateral Diffusion Junctions
AssigneeJDS Uniphase Corporation
InventorsSyn-Yem Hu, Zhong Pan
Life of this patent
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Abstract
The present invention relates to a stable mesa-type photodetector with lateral diffusion junctions. The invention has found that without resorting to the complicated regrowth approach, a simple Zn diffusion process can be used to create high-quality semiconductor junction interfaces at the exposed critical surface or to terminate the narrow-bandgap photon absorption layers. The invention converts the epi material layers near or at the vicinity of the etched mesa trench or etched mesa steps into a different dopant type through impurity diffusion process. Preferably the diffused surfaces are treated with a subsequent surface passivation. This invention can be applied to both top-illuminating and bottom-illuminating configurations.
Claims16
A mesa-type PIN photodiode comprising:
- an epitaxial semiconductor layer structure including the following layers over a substrate:
- a buffer layer;
- an absorption layer;
- a grading layer;
- and a window layer;
- a mesa structure, including a light input window to a diffused p-n junction in the window layer, defined by a trench through the epitaxial layers, the mesa having sidewalls in the trench, and the side walls including a diffusion margin of p-type material terminating the lateral extent of the epitaxial layers of the mesa;
- a p-contact disposed for electrical contact to the p-n junction;
- and
- an n-contact disposed for electrical contact to the p-n junction.
A method of passivating the etched sidewalls of a mesa-type PIN photodiode comprising the steps of:
- providing a passivation layer over an epitaxial semiconductor layer stack on a substrate including:
- a buffer layer, an absorption layer, a grading layer and a window layer;
- opening a window in the passivation layer and etching a trench in the semiconductor layers to create a mesa;
- diffusing a dopant into the trench to form a diffusion margin of p-type material in the sidewalls of the mesa;
- opening a window in the passivation layer over the mesa;
- diffusing a dopant in through the window over the mesa to create a diffused active region in the window layer comprising a light input window to a diffused p-n junction in the window layer;
- applying an anti-reflection coating over the light input window;
- and
- applying p- and n-metal contacts.
Dependencies are inferred from the claim text.