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 low-concentration layer of the first conductivity type and the low-concentration layer of the second conductivity type each having a carrier concentration of less than 1×10 16 /cm 3 ,
the high-concentration layer of the first conductivity type having a higher carrier concentration than the low-concentration layer of the first conductivity type,
the high-concentration layer of the second conductivity type having a higher carrier concentration than the low-concentration layer of the second conductivity type,
the high-concentration layer of the first conductivity type and the high-concentration layer of the second conductivity type each having a carrier concentration of 1×10{circumflex over ( )}17/cm{circumflex over ( )}3 or more, and
at least one of the low-concentration layer of the first conductivity type or the low-concentration layer of the second conductivity type including 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
)
·
N
p
·
Rp
[
Equation
1
]
Rp= 1+(ε n/εp )·( 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
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 low-concentration layer of the first conductivity type is a low-concentration InGaAs absorption layer of the first conductivity type with a band gap that absorbs incident light,
the low-concentration layer of the second conductivity type is a low-concentration InGaAs absorption layer of the second conductivity type with a band gap that absorbs incident light, and
the high-concentration layer of the second conductivity type is a contact layer of the second conductivity type.
5. 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 low-concentration layer of the second conductivity type is a low-concentration InGaAs absorption layer of the second conductivity type with a band gap that absorbs incident light, and
the high-concentration layer of the second conductivity type is a contact layer of the second conductivity type.
6. The semiconductor light-receiving element of claim 5 , wherein the low-concentration wide band gap layer of the first conductivity type is made of one of InP, InAlAs, and InAlGaAs.
7. 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.
8. The semiconductor light-receiving element of claim 7 , wherein the low-concentration layer of the first conductivity type is thinner than the low-concentration layer of the second conductivity type.
9. The semiconductor light-receiving element of claim 1 , wherein one of the low-concentration layer of the first conductivity type and the low-concentration layer of the second conductivity type that is closer to a surface on which light enters is thinner than another one of the low-concentration layer of the first conductivity type and the low-concentration layer of the second conductivity type.