Avalanche photodetectors with a combined lateral and vertical arrangement
Structures for an avalanche photodetector and methods of forming a structure for an avalanche photodetector. The structure comprises a substrate having a first conductivity type, a first semiconductor layer that defines an absorption region of the avalanche photodetector, a dielectric layer between the first semiconductor layer and the substrate, a charge control region comprising a semiconductor material having a second conductivity type opposite to the first conductivity type and a different bandgap from the first semiconductor layer, and a second semiconductor layer that extends through the dielectric layer from the charge control region to the substrate. The second semiconductor layer defines a multiplication region of the avalanche photodetector.
1 . A structure for an avalanche photodetector, the structure comprising:
a substrate having a first conductivity type;
a first semiconductor layer that defines an absorption region of the avalanche photodetector;
a first contact connected to the substrate;
a second contact connected to a side edge portion of the first semiconductor layer;
a dielectric layer between the first semiconductor layer and the substrate;
a charge control region comprising a semiconductor material having a second conductivity type opposite to the first conductivity type and a different bandgap from the first semiconductor layer; and
a second semiconductor layer that extends through the dielectric layer from the charge control region to the substrate,
wherein the second semiconductor layer defines a multiplication region.
2 . The structure of claim 1 wherein the first semiconductor layer is intrinsic germanium.
3 . The structure of claim 1 wherein the second semiconductor layer is intrinsic silicon.
4 . The structure of claim 1 wherein the semiconductor material is silicon, the first conductivity type is n-type, and the second conductivity type is p-type.
5 . The structure of claim 1 wherein the charge control region is a third semiconductor layer including a first portion that is surrounded by the first semiconductor layer.
6 . The structure of claim 5 wherein the first portion of the third semiconductor layer has a first interface with the first semiconductor layer and a second interface with the second semiconductor layer.
7 . The structure of claim 6 wherein the first interface is oriented substantially orthogonal to the second interface.
8 . The structure of claim 5 wherein the third semiconductor layer includes a second portion that projects above the first semiconductor layer.
9 . The structure of claim 5 wherein the second semiconductor layer and the third semiconductor layer are arranged in a vertical layer stack.
10 . The structure of claim 1 wherein the dielectric layer adjoins the substrate along an interface, and the second semiconductor layer includes a first portion arranged above the interface.
11 . The structure of claim 10 wherein the second semiconductor layer includes a second portion arranged below the interface.
12 . The structure of claim 1 wherein the charge control region is a doped region in the second semiconductor layer.
13 . The structure of claim 12 wherein the second semiconductor layer includes a portion positioned between the doped region and the first semiconductor layer.
14 . The structure of claim 13 wherein the portion of the second semiconductor layer surrounds the doped region.
15 . The structure of claim 1 wherein the charge control region is surrounded by the first semiconductor layer.
16 . The structure of claim 1 wherein the substrate, the dielectric layer, and the first semiconductor layer define a layer stack of a germanium-on-insulator substrate.
17 . The structure of claim 1 wherein the semiconductor material is silicon, and the first semiconductor layer is intrinsic germanium.
18 . A method of forming a structure for an avalanche photodetector, the method comprising:
providing a substrate having a first conductivity type, a first semiconductor layer, and a dielectric layer between the first semiconductor layer and the substrate;
patterning the first semiconductor layer to define an absorption region of the avalanche photodetector;
forming a charge control region comprising a semiconductor material having a second conductivity type opposite to the first conductivity type and a different bandgap from the first semiconductor layer;
forming a second semiconductor layer that extends through the dielectric layer from the charge control region to the substrate, wherein the second semiconductor layer defines a multiplication region of the avalanche photodetector;
forming a first contact connected to the substrate; and
forming a second contact connected to a side edge portion of the first semiconductor layer.
19 . The method of claim 18 wherein forming the charge control region comprising the semiconductor material having the second conductivity type opposite to the first conductivity type comprises:
epitaxially growing a third semiconductor layer on the second semiconductor layer.
20 . The method of claim 18 wherein forming the charge control region comprising the semiconductor material having the second conductivity type opposite to the first conductivity type comprises:
forming a doped region in the second semiconductor layer.