Light detection element and light detection device

Patent metadata

Field	Value
Publication number	US-11450705-B2
Application number	US-202016777291-A
Country	US
Kind code	B2
Filing date	Jan 30, 2020
Priority date	Oct 16, 2018
Publication date	Sep 20, 2022
Grant date	Sep 20, 2022

Abstract

A light detection element includes a semiconductor substrate, a light absorbing layer of a first conductivity type formed on the semiconductor substrate, a cap layer of a first conductivity type formed on the light absorbing layer, and a semiconductor region of a second conductivity type formed within the cap layer and forming a pn junction with the cap layer. A depletion layer formed around the semiconductor region does not reach the light absorbing layer in a case where a reverse bias is not applied to the pn junction, and exceeds a position amounting to 50% of a thickness of the light absorbing layer from the cap layer side in a case where a reverse bias of 20 V is applied to the pn junction.

First claim

The invention claimed is:

1. A light detection device comprising:
a light detection element; and
a signal processing unit,
wherein the light detection element includes:
a semiconductor substrate;
a light absorbing layer of a first conductivity type formed on the semiconductor substrate;
a cap layer of a first conductivity type formed on the light absorbing layer; and
a first semiconductor region of a second conductivity type formed within the cap layer and forming a pn junction with the cap layer,
wherein a depletion layer formed around the first semiconductor region does not reach the light absorbing layer in a case where a reverse bias is not applied to the pn junction, and exceeds a position amounting to 50% of a thickness of the light absorbing layer from the cap layer side in a case where a reverse bias of 20 V is applied to the pn junction,
the carrier concentration of the cap layer is equal to or less than 1×10 16 cm 3 , and
the signal processing unit is configured to apply a voltage signal to the pn junction such that a state in which the depletion layer does not reach the light absorbing layer and a state in which the depletion layer reaches the light absorbing layer are alternately repeated.

2. The light detection device according to claim 1 , wherein the signal processing unit configured to acquire a detection signal output from the light detection element.

3. The light detection device according to claim 1 , wherein the depletion layer exceeds a position amounting to 80% of the thickness of the light absorbing layer from the cap layer side in a case where a reverse bias of 20 V is applied to the pn junction.

4. The light detection device according to claim 1 , wherein the light detection element further includes a relaxation layer of a first conductivity type formed between the light absorbing layer and the cap layer.

5. The light detection device according to claim 1 , wherein the light absorbing layer and the cap layer are in contact with each other.

6. The light detection device according to claim 1 , wherein a plurality of first semiconductor regions, each of which is the first semiconductor region, are formed within the cap layer, and are arranged one-dimensionally or two-dimensionally when viewed from a thickness direction of the semiconductor substrate.

7. The light detection device according to claim 1 , wherein a plurality of first semiconductor regions, each of which is the first semiconductor region, are formed within the cap layer, and are arranged one-dimensionally when viewed from a thickness direction of the semiconductor substrate, and
a width of the cap layer is smaller than a width of the semiconductor substrate in a width direction perpendicular to both the thickness direction of the semiconductor substrate and an arrangement direction of the first semiconductor regions.

8. The light detection device according to claim 7 , wherein a width of the light absorbing layer is smaller than the width of the semiconductor substrate in the width direction.

9. The light detection device according to claim 7 , wherein the light detection element further includes a third semiconductor region of a second conductivity type formed along lateral sides of the cap layer facing each other in the width direction.

10. The light detection device according to claim 7 , wherein the light detection element further includes a third semiconductor region of a second conductivity type formed along an area on which the cap layer is not formed, the area is a part of a surface of the light absorbing layer on the opposite side of the semiconductor substrate.

11. The light detection device according to claim 1 , wherein the first conductivity type is an n-type, and the second conductivity type is a p-type.

12. The light detection device according to claim 1 , wherein the light detection element further includes a second semiconductor region of a second conductivity type formed in the cap layer so as to surround the first semiconductor region when viewed from a thickness direction of the semiconductor substrate.

13. The light detection device according to claim 12 , wherein the second semiconductor region is formed along an inner surface of a groove formed in the cap layer so as to surround the first semiconductor region when viewed from the thickness direction of the semiconductor substrate.

14. The light detection device according to claim 13 , wherein the inner surface of the groove is covered with an insulating film.

15. The light detection device according to claim 13 , wherein the groove reaches a relaxation layer of a first conductivity type formed between the light absorbing layer and the cap layer.

16. The light detection device according to claim 13 , wherein the groove reaches the light absorbing layer.

17. The light detection device according to claim 1 , wherein the light detection element further includes a second semiconductor region of a second conductivity type,
wherein a plurality of first semiconductor regions, each of which is the first semiconductor region, are formed within the cap layer, and
the second semiconductor region is formed in the cap layer so as to be located between the first semiconductor regions which are next to each other when viewed from a thickness direction of the semiconductor substrate.

18. The light detection device according to claim 13 , wherein the second semiconductor region is formed along an inner surface of a groove formed in the cap layer so as to be located between the first semiconductor regions which are next to each other when viewed from the thickness direction of the semiconductor substrate.

19. The light detection device according to claim 18 , wherein the inner surface of the groove is covered with an insulating film.

20. The light detection device according to claim 18 , wherein the groove reaches a relaxation layer of a first conductivity type formed between the light absorbing layer and the cap layer.

21. The light detection device according to claim 18 , wherein the groove reaches the light absorbing layer.

22. The light detection device according to claim 1 , wherein the cap layer includes:
a first region; and
a second region formed on the semiconductor substrate side with respect to the first region so as to be in contact with the first region and to include a surface of the cap layer on the semiconductor substrate side,
the first region and the second region are not sensitive to light to which the light absorbing layer is sensitive,
a composition of the second region is different from a composition of the first region, and
the first semiconductor region is formed within the first region so that an end of the first semiconductor region on the semiconductor substrate side reaches the second region.

23. The light detection device according to claim 1 , wherein the cap layer includes:
a first region; and
a second region formed within the first region,
wherein the first region is not sensitive to light to which the light absorbing layer is sensitive,
a composition of the second region is different from a composition of the first region, and
the first semiconductor region is formed within a region of the first region located on the opposite side of the semiconductor substrate with respect to the second region so that an end of the first semiconductor region on the semiconductor substrate side reaches the second region.

24. The light detection device accord

Assignees

• Hamamatsu Photonics Kk

Inventors

• Mase Mitsuhito
• TAGUCHI Keiki
• Ishihara Hajime
• Yamamoto Hiroo
• Shimada Akihiro

Classifications

• G01J1/44

  Electric circuits {(for command of an exposure part G03B7/02)} · CPC title

• G01S17/89

  for mapping or imaging · CPC title

• G01S17/08

  for measuring distance only (indirect measurement G01S17/46; active triangulation systems G01S17/48) · CPC title

• G01S7/481

  Constructional features, e.g. arrangements of optical elements · CPC title

• H01L31/109

  Electricity · mapped topic