Photo detector

Abstract

A photo detector is provided with a plurality of quantum dot layers and first conductive type contact layers provided at both sides of the plurality of quantum dot layers so as to sandwich them; a second conductive type impurity is doped in a first semiconductor layer formed between one first conductive type contact layer and a first quantum dot layer which is closest to the one first conductive type contact layer so that it results in a barrier against a carrier positioned at the one first conductive contact layer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view showing a configuration of a photo detector (quantum dot infrared detector) according to a first embodiment of the present invention;

FIG. 2 is a diagram showing a conduction band edge profile of a photo detector (quantum dot infrared detector) with being doped p-type impurity according to the first embodiment of the present invention;

FIG. 3 is a diagram showing a conduction band edge profile of a photo detector (quantum dot infrared detector) with being doped p-type impurity and n-type impurity according to the first embodiment of the present invention;

FIG. 4 is a diagram showing a conduction band edge profile of a photo detector (quantum dot infrared detector) with being applied a potential difference according to the first embodiment of the present invention;

FIG. 5 is a schematic cross-sectional view for illustrating a method for fabrication of a photo detector (quantum dot infrared detector) according to the first embodiment of the present invention;

FIG. 6 is a schematic cross-sectional view for illustrating a structure and its method for fabrication of a photo detector (a quantum dot infrared detector) according to the first embodiment of the present invention;

FIG. 7 is a schematic cross-sectional view showing a structure of a photo detector (a quantum dot infrared detector) according to a second embodiment of the present invention;

FIG. 8 is a diagram showing a conduction band edge profile of a photo detector (a quantum dot infrared detector) with being doped p-type impurity and n-type impurity according to the second embodiment of the present invention;

FIG. 9(A) is a diagram showing a conduction band edge profile of a photo detector (quantum dot infrared detector) with being applied a positive potential difference according to the second embodiment of the present invention;

FIG. 9(B) is a diagram showing a conduction band edge profile of a photo detector (quantum dot infrared detector) with being applied a negative potential difference according to the second embodiment of the present invention;

FIG. 10 is a schematic cross-sectional view showing a structure of a photo detector (quantum dot infrared detector) according to a third embodiment of the present invention;

FIG. 11 is a diagram showing a valence band edge profile of a photo detector (quantum dot infrared detector) with being doped p-type impurity and n-type impurity according to the third embodiment of the present invention;

FIG. 12 is a diagram showing a valence band edge profile of a photo detector (quantum dot infrared detector) with being applied a potential difference according to the third embodiment of the present invention;

FIG. 13(A) is a diagram showing a conduction band edge profile of a conventional quantum dot infrared detector;

FIG. 13(B) is a schematic cross-sectional view showing a structure of a conventional quantum dot infrared detector; and

FIG. 14 is a diagram showing a conduction band edge profile of the conventional quantum dot infrared detector with being applied a potential difference.

Claims

1. A photo detector comprising: a plurality of quantum dot layers having quantum dots; andfirst conductive type contact layers provided to sandwich the plurality of quantum dot layers on the opposite sides,wherein a second conductive type impurity is doped in a first semiconductor layer formed between the one of the first conductive type contact layers and the closest first quantum dot layer to the one of the first conductive type contact layers to form barrier against carriers positioned in one of the first conductive type contact layers.

2. The photo detector according to claim 1, wherein a first conductive type impurity is doped in quantum dot layers formed between the first semiconductor layer and the other of the first conductive type contact layers.

3. The photo detector according to claim 2, wherein, the one of the first conductive type contact layers is a n-type contact layer which becomes low potential when a potential difference is applied therebetween;the first quantum dot layer is the closest quantum dot layer to the n-type contact layer of the low potential;the first semiconductor layer is formed between the n-type contact layer of the low potential and the first quantum dot layer;the second conductive type impurity is p-type impurity; andthe first conductive type impurity is n-type impurity.

4. The photo detector according to claim 2, wherein, the one of the first conductive type contact layers is a p-type contact layer which becomes high potential when a potential difference is applied therebetween;the first quantum dot layer is the closest quantum dot layer to the p-type contact layer of the high potential;the first semiconductor layer is formed between the p-type contact layer of the high potential and the first quantum dot layer;the second conductive type impurity is n-type impurity; andthe first conductive type impurity is p-type impurity.

5. The photo detector according to claim 1, wherein a second conductive type impurity is doped in a second semiconductor layer formed between the other of the first conductive type contact layers and quantum dots which compose the closest second quantum dot layer to the other of the first conductive type contact layers to form barrier against carriers positioned in the other of the first conductive type contact layers.

6. The photo detector according to claim 5, wherein the second quantum dot layer has a buried layer which buries the quantum dots and the second semiconductor layer is the buried layer.

7. The photo detector according to claim 5, wherein a first conductive type impurity is doped in a quantum dot layer formed between the second semiconductor layer and the first semiconductor layer.

8. The photo detector according to claim 7, wherein, the first conductive type contact layer is a n-type contact layer;the second conductive type impurity is p-type impurity; andthe first conductive type impurity is n-type impurity.

9. The photo detector according to claim 7, wherein, the first conductive type contact layer is a p-type contact layer;the second conductive type impurity is n-type impurity; andthe first conductive type impurity is p-type impurity.

10. The photo detector according to claim 1, wherein the quantum dot layer includes a cap layer which covers the quantum dots, and an intermediate layer which is formed on the cap layer.

11. The photo detector according to claim 1, wherein the quantum dots are made from InAs; and the contact layer and the intermediate layer are made from GaAs.

12. A quantum dot infrared photo detector comprising the configuration according to claim 1.