Enhanced photodetector

A photodiode comprising:

• a first p-type semiconductor layer;
• an n-type semiconductor layer;
• and
• a second p-type semiconductor layer disposed between the first p-type semiconductor layer and the n-type semiconductor layer such that the second p-type semiconductor is directly adjacent to the n-type semiconductor, the second p-type semiconductor layer having a graded doping concentration,
• the graded doping concentration defining a first concentration adjacent to the first p-type semiconductor layer and a second concentration adjacent to the n-type semiconductor layer, the first concentration being greater than the second concentration, and
• the first concentration being located at a position xo and defining a concentration Po, and the graded doping concentration being governed by the following equation:
• p
• =
• p
• o
• ⁢
• ⅇ
• -
• x
• D
• over the depth D of the second p-type semiconductor layer for all x and D greater than zero.

A method of fabricating a photodiode comprising:

• providing a substrate layer;
• depositing an n-type semiconductor layer on the substrate;
• depositing a second p-type semiconductor layer having a p-type dopant on the n-type semiconductor layer;
• grading the p-type dopant of the second p-type semiconductor layer from a first concentration to a second concentration, the first concentration being greater than the second concentration;
• and
• depositing a first p-type semiconductor layer on the second p-type semiconductor layer, the second p-type semiconductor layer being between the first p-type semiconductor layer and the n-type semiconductor layer such that the second concentration is directly adjacent to the n-type semiconductor layer.

A method of fabricating a photodiode comprising:

• providing a substrate layer;
• depositing an n-type semiconductor layer on the substrate;
• depositing a second p-type semiconductor layer having a p-type dopant on the n-type semiconductor layer;
• grading the p-type dopant of the second p-type semiconductor layer from a first concentration to a second concentration, wherein the first concentration is greater than the second concentration;
• and
• depositing a first p-type semiconductor layer on the second p-type semiconductor layer, wherein the second p-type semiconductor layer is between the first p-type semiconductor layer and the n-type semiconductor layer such that the second concentration is directly adjacent to the n-type semiconductor layer, and
• wherein the first concentration is located at a position xo and defines a concentration Po, and further wherein the graded doping concentration is governed by the following equation:
• p
• =
• p
• o
• ⁢
• ⅇ
• -
• x
• D
• over the depth D of the second p-type semiconductor layer for all x and D greater than zero.

A photodiode having a first p-type semiconductor layer and an n-type semiconductor layer comprising:

• a second p-type semiconductor layer disposed between the first p-type semiconductor layer and the n-type semiconductor layer such that the second p-type semiconductor is directly adjacent to the n-type semiconductor, the second p-type semiconductor layer having a graded doping concentration, wherein the graded doping concentration is governed by the following equation:
• p
• =
• p
• o
• ⁢
• ⅇ
• -
• x
• D
• over the depth D of the second p-type semiconductor layer for all x and D greater than zero.