Charge controlled avalanche photodiode and method of making the same
The present invention includes an epitaxial structure ( 16 ) grown on a semi-insulating InP substrate ( 12 ). First, a buffer layer ( 14 ) is grown to isolate defects originated from substrates ( 12 ). Then an n-type layer ( 18 ) is grown to serve as n-contact layer to collect electrons. Next, a multiplication layer ( 20 ) is grown to provide avalanche gain for the APD device ( 10 ). Following that, an ultra-thin charge control layer ( 22 ) is grown with carbon doping. An absorption layer ( 24 ) is grown to serve as the region for creating electronhole pairs due to a photo-excitation. Finally, a p-type layer ( 28 ) is grown to serve as p-contact layer to collect holes.
1 . An avalanche photodiode comprising:
an absorption layer disposed on a substrate layer;
a multiplication layer disposed on the substrate layer; and
a carbon-doped charge control layer disposed between the absorption layer and the multiplication layer.
2 . The avalanche photodiode of claim 1 wherein the absorption layer is disposed between a first digital graded layer and a second digital graded layer.
3 . The avalanche photodiode of claim 1 further comprising an n-type contact layer disposed between the multiplication layer and the substrate.
4 . The avalanche photodiode of claim 1 further comprising a p-type contact layer.
5 . The avalanche photodiode of claim 1 further comprising a buffer layer disposed between the n-type contact layer and the substrate.
6 . The avalanche photodiode of claim 1 wherein the absorption layer is InGaAs.
7 . The avalanche photodiode of claim 1 wherein the multiplication layer is InAlAs.
8 . The avalanche photodiode of claim 1 wherein the carbon-doped charge control layer is carbon-doped InAlAs.
9 . The avalanche photodiode of claim 1 wherein the carbon-doped charge control layer is between 2 and 100 angstroms in thickness.
10 . The avalanche photodiode of claim 1 wherein the carbon-doped charge control layer is between 5 and 50 angstroms in thickness.
11 . The avalanche photodiode of claim 1 wherein the carbon-doped charge control layer is between 5 and 35 angstroms in thickness.
12 . The avalanche photodiode of claim 2 wherein the first digital graded layer is InAlGaAs, and further wherein the second digital graded layer is InAlGaAs.
13 . The avalanche photodiode of claim 3 wherein the n-type contact layer is one of InP or InAlA.
14 . The avalanche photodiode of claim 4 wherein the p-type contact layer is one of InP or InAlAs.
15 . A method of fabricating an avalanche photodiode comprising the steps of:
providing a substrate layer;
depositing a multiplication layer;
depositing a carbon-doped charge control layer; and
depositing an absorption layer.
16 . The method of claim 15 further comprising the step of depositing an n-type layer to collect electrons.
17 . The method of claim 15 further comprising the step of depositing a p-type layer to collect holes.
18 . The method of claim 15 further comprising the step of depositing a digital grading layer to prevent carrier trapping between bandgap offsets.
19 . The method of claim 15 further comprising the step of doping an InAlAs material with carbon.