Semiconductor light-receiving element
A semiconductor light-receiving element, includes: a semiconductor substrate; a high-concentration layer of a first conductivity type formed on the semiconductor substrate; a low-concentration layer of the first conductivity type formed on the high-concentration layer of the first conductivity type and in contact with the high-concentration layer of the first conductivity type; a low-concentration layer of a second conductivity type configured to form a PN junction interface together with the low-concentration layer of the first conductivity type; and a high-concentration layer of the second conductivity type formed on the low-concentration layer of the second conductivity type and in contact with the low-concentration layer of the second conductivity type. The low-concentration layers have a carrier concentration of less than 1×10 16 /cm 3 . The high-concentration layers have a carrier concentration of 1×10 17 /cm 3 or more. At least one of the low-concentration layers includes an absorption layer with a band gap that absorbs incident light.
1. A semiconductor light-receiving element, comprising:
a semiconductor substrate;
a high-concentration layer of a first conductivity type formed on the semiconductor substrate;
a low-concentration layer of the first conductivity type formed on the high-concentration layer of the first conductivity type and in contact with the high-concentration layer of the first conductivity type;
a low-concentration layer of a second conductivity type configured to form a PN junction interface together with the low-concentration layer of the first conductivity type; and
a high-concentration layer of the second conductivity type formed on the low-concentration layer of the second conductivity type and in contact with the low-concentration layer of the second conductivity type, wherein:
the high-concentration layer of the first conductivity type has a carrier concentration that is higher than a carrier concentration of the low-concentration layer of the first conductivity type,
the high-concentration layer of the second conductivity type has a carrier concentration that is higher than a carrier concentration of the low-concentration layer of the second conductivity type, and
one or both of the low-concentration layer of the first conductivity type or the low-concentration layer of the second conductivity type includes an absorption layer with a band gap that absorbs incident light.
2. The semiconductor light-receiving element of claim 1 ,
wherein the low-concentration layer of the first conductivity type has a thickness that is 1.1 times a thickness Dn0 or less, the thickness Dn0 being defined by Equation 1, Equation 2, and Equation 3, and
wherein the low-concentration layer of the second conductivity type has a thickness that is 1.1 times a thickness Dp0 or less, the thickness Dp0 being defined by Equation 1, Equation 2, and Equation 3:
Dp
0
=
2
·
(
Vr
+
Vb
)
(
q
ε
p
)
·
Np
·
Rp
[
Equation
1
]
Rp
=
1
+
(
ε
n
/
ε
p
)
·
(
Np
/
Nn
)
[
Equation
2
]
Dn
0
=
(
Rp
-
1
)
·
Dp
0
[
Equation
3
]
wherein:
Vr: bias voltage applied from outside,
Vb: built-in potential,
q: elementary charge,
εp: dielectric constant of the low-concentration layer of the second conductivity type, and
εn: dielectric constant of the low-concentration layer of the first conductivity type.
3. The semiconductor light-receiving element of claim 2 ,
wherein the thickness of the low-concentration layer of the first conductivity type is the thickness Dn0 or less, and
wherein the thickness of the low-concentration layer of the second conductivity type is the thickness Dp0 or less.
4. The semiconductor light-receiving element of claim 1 , wherein:
the high-concentration layer of the first conductivity type is a contact layer of the first conductivity type,
the high-concentration layer of the second conductivity type is a contact layer of the second conductivity type, and
both of the low-concentration layer of the first conductivity type and the low-concentration layer of the second conductivity type include an absorption layer with a band gap that absorbs incident light.
5. The semiconductor light-receiving element of claim 4 , wherein, for each of the low-concentration layer of the first conductivity type and the low-concentration layer of the second conductivity type, the absorption layer is a low-concentration InGaAs absorption layer.
6. The semiconductor light-receiving element of claim 1 , wherein:
the high-concentration layer of the first conductivity type is a contact layer of the first conductivity type,
the low-concentration layer of the first conductivity type is a low-concentration wide band gap layer of the first conductivity type with a band gap that does not absorb incident light,
the high-concentration layer of the second conductivity type is a contact layer of the second conductivity type, and
one of the low-concentration layer of the first conductivity type or the low-concentration layer of the second conductivity type includes an absorption layer with a band gap that absorbs incident light,
wherein the one includes the low-concentration layer of the second conductivity type.
7. The semiconductor light-receiving element of claim 6 , wherein the absorption layer is a low-concentration InGaAs absorption layer.
8. The semiconductor light-receiving element of claim 6 , wherein the low-concentration wide band gap layer of the first conductivity type is made of one of InP, InAlAs, or InAlGaAs.
9. The semiconductor light-receiving element of claim 1 , wherein:
the high-concentration layer of the first conductivity type is a contact layer of the first conductivity type,
the low-concentration layer of the first conductivity type is a low-concentration wide band gap layer of the first conductivity type with a band gap that does not absorb incident light,
the high-concentration layer of the second conductivity type is a contact layer of the second conductivity type and is a first high-concentration layer of the second conductivity type,
one of the low-concentration layer of the first conductivity type or the low-concentration layer of the second conductivity type includes an absorption layer with a band gap that absorbs incident light,
wherein the one is the low-concentration layer of the second conductivity type; and
the semiconductor light-receiving element further comprises:
a second high-concentration layer of the second conductivity type formed on the first high-concentration layer of the second conductivity type and in contact with the first high-concentration layer of the second conductivity type.
10. The semiconductor light-receiving element of claim 9 , wherein the low-concentration wide band gap layer of the first conductivity type is made of one of InP, InAlAs, or InAlGaAs.
11. The semiconductor light-receiving element of claim 1 , wherein the first conductivity type is an n-type, and the second conductivity type is a p-type.
12. The semiconductor light-receiving element of claim 11 , wherein the low-concentration layer of the first conductivity type has a thickness that is less than a thickness of the low-concentration layer of the second conductivity type.
13. The semiconductor light-receiving element of claim 12 , wherein the carrier concentration of the low-concentration layer of the first conductivity type is greater than the carrier concentration of the low-concentration layer of the second conductivity type.
14. The semiconductor light-receiving element of claim 11 , wherein the low-concentration layer of the first conductivity type has a thickness that is greater than a thickness of the low-concentration layer of the second conductivity type.
15. The semiconductor light-receiving element of claim 14 , wherein the carrier concentration of the low-concentration layer of the first conductivity type is less than the carrier concentration of the low-concentration layer of the second conductivity type.
16. The semiconductor light-receiving element of claim 1 , wherein the low-concentration layer of the first conductivity type has a thickness that is different than a thickness of the low-concentration layer of the second conductivity type.
17. The semiconductor light-receiving element of claim 1 , wherein the carrier concentration of the low-concentration layer of the first conductivity type is different than the carrier concentration of the low-concentration layer of the second conductivity type.
18. The semiconductor light-receiving element of claim 1 , wherein the carrier concentration of each of the low-concentration layer of the first conductivity type and the low-concentration layer of the second conductivity type is less than 1×10 16 /cm 3 .
19. The semiconductor light-receiving element of claim 1 , wherein the carrier concentration of each of the high-concentration layer of the first conductivity type and the high-concentration layer of the second conductivity type is greater than or equal to 1×10 16 /cm 3 .
20. The semiconductor light-receiving element of claim 19 , wherein the carrier concentration of each of the low-concentration layer of the first conductivity type and the low-concentration layer of the second conductivity type is less than 1×10 16 /cm 3 .