JPH0513806A - Semiconductor photoelector - Google Patents

Abstract

PURPOSE:To attain increase in the ionization ratio, relief of hole pile up and decrease in hole running time in the super lattice APD thereby attaining the broader band and the lower noise. CONSTITUTION:Within an avalanche multiplication photodetector structure, a p type InGaAs photoabsorption layer 14 and an InAlAs/InGaAs hetero periodic structured avalanche multiplication layer 15 are provided on a p type InP substrate 12. At this time, the composition of InxGa1-xAs layer as a well layer of the avalanche doubled layer 15 is to be x=0.458 while the composition of InyAl1-yAs layer as a tensile stress and barrier layers is to be y=0.595 so as to load the compressive stress. Besides, the conduction band discontinuous energy DELTAEv will be 30meV less than the non-distortion energy (0.207eV). Furthermore, since the light hole band is to be the basic level in said well layer, hole pile up is relieved and hole running time is shortened. Through these procedures, the high sensitivity characteristics in broader band and lower noise can be displayed.

Description

Detailed Description of the Invention

[0001]

The present invention relates to optical communication, optical information processing,
The present invention relates to a semiconductor light receiving element used in optical measurement and the like, and particularly to an avalanche multiplication type semiconductor light receiving element excellent in low noise and high-speed response.

[0002]

2. Description of the Related Art Conventionally, as a semiconductor light receiving element for optical communication in the wavelength range of 1 to 1.6 μm, a lattice-matched I on an InP substrate has been used.
_{.. n 0 5 3 Ga 0} 4 7 PIN type semiconductor photodetector As layer (hereinafter referred to as InGaAs layer) and a light absorbing layer (Electronics Letters -'s (Electronics L
etters) 1984, 20 volumes, pp653-65
4), an avalanche multiplication type semiconductor photodetector (II-EE electron device letter (I
EEE. Electron Device Lette
rs) 1986, Volume 7, pp 257-258)
It has been known. In particular, the latter is practically used for long-distance communication because it has an internal gain effect due to the avalanche multiplication effect and a high-speed response.

FIG. 7 is a structural diagram of a typical InGaAs-APD (the avalanche multiplication type semiconductor light receiving element is referred to as AP below).
Abbreviated as D. ) Is shown. The operating principle is that among the photocarriers generated in the InGaAs light absorption layer 3, hole carriers are injected into the InP avalanche layer 4 by the electric field. Since a high electric field is applied to the InP avalanche layer 4, ionization collision occurs, which leads to multiplication characteristics. In this case, it is known that the noise and fast response characteristics, which are important in device characteristics, are governed by the random ionization process of carriers in the multiplication process. Specifically, the greater the difference between the ionization rates of electrons and holes in the InP layer, which is the multiplication layer, the greater the ionization rate ratio becomes (if the ionization rates of electrons and holes are α and β, respectively, α / When β> 1, electrons should be the main carriers when β / α> 1, and holes should be the main carriers that cause ionization collision when β / α> 1).

However, the ionization ratio (α / β or β
/ Α) is determined by the physical properties of the material, and is at most about β / α = 2 for InP. This is largely different from α / β = 20 of Si having low noise characteristics, and epoch-making material technology is required to realize lower noise and high-speed response characteristics. On the other hand, F. Capa
et al., band discontinuity energy (ΔE) of the conduction band.
c) is used to promote electron ionization, and the ionization ratio (α
We propose a superlattice APD aiming at high sensitivity and wide band by increasing / β). An example is Applied Physics Letters (Applied Physics).
Letters), 1982, vol. 40, p38. On the other hand, it is known that the band structure is changed by applying strain stress in the semiconductor superlattice structure, and in particular, the degeneration of the heavy hole band and the light hole band can be solved in the valence band energy band. An example is the Journal of Applied Physics.
Ysics), 1990, 67, p344.

[0005]

As described in the section of the prior art, in the superlattice APD, the band discontinuity energy (ΔEc) of the conduction band greatly contributes to the improvement of the ionization ratio. On the other hand, the discontinuity energy of the valence band (ΔE
Due to v), pile-up of holes occurs, and there is a problem of degrading the band during multiplication.

The object of the present invention is to increase the conduction band discontinuity energy by applying a strain stress to further improve the ionization ratio, or to bring the light hole band into the ground level to make the hole pile at ΔEv. An object of the present invention is to provide an avalanche multiplication type semiconductor light receiving element having low noise and high speed response by reducing up-time and shortening traveling time.

[0007]

The light receiving element of the present invention is a semiconductor light receiving element comprising a light absorption layer and a hetero periodic structure avalanche multiplication semiconductor layer on a semiconductor substrate, wherein the hetero periodic structure avalanche multiplication layer is provided. The average ionization energies of the group III atom and the group V atom of the first semiconductor layer are E _A and E _B , respectively, and III of the second semiconductor layer is III.
When the average ionization energies of the group atom and the group V atom are E _C and E _D , respectively, the relationship of E _A > E _C and E _B <E _D holds, and the tensile stress and the A compressive stress is applied to the second semiconductor layer.

Alternatively, the light receiving element of the present invention is a semiconductor light receiving element comprising a light absorption layer and a heteroperiodic structure avalanche multiplication semiconductor layer on a semiconductor substrate, wherein the heteroperiodic structure avalanche multiplication layer is formed. The average ionization energies of group III atoms and group V atoms of the semiconductor layer of E _A and E _B respectively, and the average ionization energies of group III atoms and group V atoms of the second semiconductor layer E _C respectively.
And when the E _D, holds the relationship of E _A> E _C and E _B <E _D, and, the tensile stress to said first semiconductor layer to compressive stress and said second semiconductor layer is loaded Is characterized by.

Alternatively, the light-receiving element of the present invention is a semiconductor light-receiving element having a light absorption layer and a heteroperiodic structure avalanche multiplication semiconductor layer on a semiconductor substrate, wherein the heteroperiodic structure avalanche multiplication layer is formed. Of the semiconductor layer of
When the average ionization energies of the group II atom and the group V atom are E _A and E _B , and the average ionization energies of the group III atom and the group V atom of the second semiconductor layer are E _C and E _D , respectively, E _A > E holds the relationship of _C and E _B <E _D, and a semiconductor light receiving element, characterized in that tensile stress in the stress and said second semiconductor layer tensile said first semiconductor layer is loaded.

Alternatively, the light receiving element of the present invention is a semiconductor light receiving element comprising a light absorption layer and a heteroperiodic structure avalanche multiplication semiconductor layer on a semiconductor substrate, wherein the heteroperiodic structure avalanche multiplication layer is formed. Of the semiconductor layer of
When the average ionization energies of the group II atom and the group V atom are E _A and E _B , and the average ionization energies of the group III atom and the group V atom of the second semiconductor layer are E _C and E _D , respectively, E _A > The relationship of E _C and E _B <E _D is established, the compressive stress is applied to the first semiconductor layer, the conduction band discontinuity energy is larger than that of no strain, and the ionization rate ratio can be improved. .

[0011]

1 is a view for explaining the band structure of the light receiving element according to claim 1 of the present invention. The right side is a band diagram of the device of the present invention, and the left side is a band diagram for comparison without distortion. The avalanche multiplication layer has a hetero-periodic structure, and as an example of a specific example satisfying the above band structure, In _x Ga _{1 -x} As (0 ≦ x ≦ 1) is added to the first semiconductor layer,
In the second semiconductor layer, In _y Al _{1 -y} As (0 ≦ y ≦ 1)
Is used. The traveling electrons feel the discontinuity energy ΔEc of the conduction band and can obtain the ionization energy corresponding to the energy, so that the α / β ratio can be made large. Here, the first semiconductor layer (well layer) is In
_{0. 4 5 8} Ga _0. And _{5 4 2} As, loaded with 0.5% tensile stress, the second semiconductor layer (barrier layer) an In
_{0. 5 95 Al 0. 4} 0 5 and As, when loaded with 0.5% compressive stress, valence band discontinuity energy ΔEv is a 0.177EV, 30 meV than ΔEv in the case of unstrained
Get smaller.

Further, since the light hole band of the well layer is on the higher energy side of 36 meV than the heavy hole band, that is, the ground level, the mass of the electrons in the well layer becomes light and the valence band discontinuity occurs. The pile-up of holes due to the energy ΔEv is alleviated.

[0013] Regarding this band change, Kao et al., Journal of Applied Physics (Jour.
nal of Applied Physics) 57
Volume (1985) p. 5428, or Wan et al., Journal of Applied Physics (Jour
nal of Applied Physics) 67
Vol. (1990) p. 344.

Also, the InGaAs well layer and InAlAs
Since the strain direction of the barrier layer is opposite, no strain effect is exerted on the layers other than the MQW multiplication layer, and good crystallinity is maintained. Naturally, the MQW critical film thickness is theoretically infinite as well as no strain.

FIG. 2 is a diagram for explaining a band structure of a light receiving element according to claim 2 of the present invention. The right is a band diagram of the element of the present invention, and the left is the case of an element without distortion. The avalanche multiplication layer has a hetero-periodic structure, and as an example of a specific example satisfying the above band structure, the first semiconductor layer has an I
n _x Ga _{1 -x} As (0 ≦ x ≦ 1) and In _y Al _{1 -y} As (0 ≦ y ≦ 1) are used for the second semiconductor layer. The traveling electrons feel the discontinuity energy ΔEc of the conduction band and can obtain the ionization energy corresponding to the energy, so that the α / β ratio can be made large. Here, the first semiconductor layer (well layer) In _{0. 6 0 3} Ga
0.39 ₇ As, 0.5% compressive stress is applied, and the second semiconductor layer (barrier layer) is made of In _0.447 Al.
_When 0.55 As and 0.5% tensile stress are applied, the conduction band discontinuity energy ΔEc is 0.637e.
V is 0.125 eV larger than the strain-free ΔEc, and the ionization ratio can be further increased.

In the hole layer of the barrier layer, the light hole band is on the higher energy side of 33 meV than the heavy hole band, that is, the ground level is taken. Therefore, the mass of electrons in the barrier layer is reduced, and the transit time of the barrier layer is reduced. Will be reduced. This band change has been reported by Kao and Wang et al. In the aforementioned Journal of Applied Physics.

Further, the InGaAs well layer and InAlAs
Since the strain direction of the barrier layer is opposite, no strain effect is exerted on the layers other than the MQW multiplication layer, and good crystallinity is maintained. Naturally, the MQW critical film thickness is theoretically infinite as well as no strain.

FIG. 3 is a diagram for explaining a band structure of a light receiving element according to claim 3 of the present invention. The right is a band diagram of the element of the present invention, and the left is the case of the element without distortion. The avalanche multiplication layer has a hetero-periodic structure, and as one example of a specific example satisfying the band structure described above, In _x Ga _{1 -x} As (0 ≦ x ≦ 1) is formed in the first semiconductor layer and the second semiconductor layer is formed. In _y Al _{1 -y} As (0 ≦ y ≦ 1) is used. The traveling electron has a discontinuity energy ΔEc in the conduction band.
It is possible to obtain the ionization energy corresponding to that energy, so that the α / β ratio can be increased. Here, the first semiconductor layer (well layer) is In
_{0. 4 5 8} Ga _0. And _{5 4 2} As, loaded with 0.5% tensile stress, the second semiconductor layer (barrier layer) an In
_{0.44 7} Al 0.55 ₃ As and 0.5% tensile stress is applied, conduction band discontinuity energy ΔEc
Is 0.596 eV, which is 84 me from ΔEc without distortion.
V becomes large, and the ionization ratio can be made large. Further, the hole bands of the well layer and the barrier layer are higher in the light hole band by 36 meV and 33 meV than the heavy hole band, that is, they take the ground level, so that the mass of electrons in the well layer and the barrier layer is light. Becomes
The running time in the multiplication layer is reduced. On the other hand, when the 0.5% strain is applied, the critical film thickness is about 0.7 μm.
If the multiplication layer thickness is less than this, dislocations are not introduced and good crystallinity can be maintained.

[0019]

The first embodiment of the present invention will be described in detail with reference to the drawings. FIG. 4 is a sectional view of an avalanche multiplication type light receiving element according to an embodiment of the present invention of claim 1. The fabrication process is as follows: p-type InP substrate 12 has a p-type InP buffer layer 13 of 0.5 μm, p-type InGaAs light absorption layer 14 of 1.5 μm, and InAlAs400A (angstrom) / InGaAs200A 16-period heteroperiod avalanche multiplication structure. The layer 15 is sequentially laminated by 1.0 μm, and the cap layer 16 is sequentially laminated by 0.5 μm. Here, In _x Ga that is a well layer (first layer) of the avalanche multiplication layer 15 is used.
The composition of the _1-x As layer was x = 0.458, and a tensile stress of 0.5% was applied. Further, In _y Al _{1 -y} As which is the barrier layer (second layer) of the avalanche multiplication layer
The composition of the layer was y = 0.595, and a compressive strain of 0.5% was applied.

Next, in order to form the n ^-- type guard ring region 17, Si is added at 1 × 10 ¹³ cm at an acceleration voltage of 100 kV.
^{- 2,} and ion implantation to a depth of 3000A, 5 × 10
A concentration region of ¹⁶ cm ^-3 is obtained. Similarly, in order to form the n ⁺ light receiving region 18, 1 × 1 of Si is applied at an acceleration voltage of 200 kV.
0 ¹⁴ cm ^-2 , ion-implanted to a depth of 0.5 μm,
A concentration region of 1 × 10 ¹⁸ cm ⁻³ is obtained. Further, a passivation film 8 of 1500 A is formed, and AuGe / Ni of 1500 A and TiPtAu of 50 are used as the n-side electrode 9.
0A is deposited. Further, the device structure shown in FIG. 4 is completed by depositing 1,500 A of AuZn as the p-side electrode 10.

Under the above-mentioned device structure, the pile-up of holes due to the valence band discontinuity energy (ΔEv) was alleviated by the principle described in the action, and the band at the time of multiplication was improved. Further, the transit time of holes in the barrier layer was reduced, and a further improvement in the band was obtained. As a result, the maximum band is 13 GHz, the GB product is 100 GHz, and the ionization ratio (α
/ β) 7, low noise with a quantum efficiency of 75%, and high-speed response characteristics have been realized. Specifically, the device structure according to the present invention is a MOVP.
It can be produced by a growth technique such as E, MBE or gas source MBE.

The second embodiment of the present invention will be described in detail with reference to the drawings. FIG. 5 is a sectional view of an avalanche multiplication type light receiving element according to an embodiment of the present invention. In the manufacturing process, the p-type InP buffer layer 13 is formed on the p-type InP substrate 12 by 0.5 μm, and the p-type InGaAs light absorption layer 14 is formed.
1.5 .mu.m, InAlAs400A (angstrom) / InGaAs200A 16-period heteroperiodic structure avalanche multiplication layer 15 of 1.0 .mu.m, and a cap layer 16 of 0.5 .mu.m are sequentially laminated. Here, In _x Ga that is a well layer (first layer) of the avalanche multiplication layer 15 is used.
The composition of the _1-x As layer was x = 0.603, and a compressive stress of 0.5% was applied. The composition of the In _y Al _{1 -y} As layer, which is the barrier layer (second layer) of the avalanche multiplication layer, was y = 0.447, and 0.5% tensile strain was applied.

Next, in order to form the n ^-- type guard ring region 17, Si is added at 1 × 10 ¹³ cm at an acceleration voltage of 100 kV.
^{- 2,} and ion implantation to a depth of 3000A, 5 × 10
A concentration region of ¹⁶ cm ^-3 is obtained. Similarly, in order to form the n ⁺ light receiving region 18, 1 × 1 of Si is applied at an acceleration voltage of 200 kV.
0 ¹⁴ cm ^-2 , ion-implanted to a depth of 0.5 μm,
A concentration region of 1 × 10 ¹⁸ cm ⁻³ is obtained. Further, a passivation film 8 of 1500 A is formed, and AuGe / Ni of 1500 A and TiPtAu of 50 are used as the n-side electrode 9.
0A is deposited. Further, the device structure shown in FIG. 4 is completed by depositing 1,500 A of AuZn as the p-side electrode 10.

The conduction band discontinuity energy (ΔEc) was increased and the ionization ratio was improved by the principle described in the operation under the above-described device structure. Further, the transit time of holes in the barrier layer was reduced, and the band was improved. As a result, an avalanche multiplication type semiconductor light receiving element having a maximum band of 12 GHz, a GB product of 100 GHz, an ionization rate ratio (α / β) of 10, low noise with a quantum efficiency of 75%, and high-speed response characteristics was realized. Specifically, the device structure according to the present invention can be manufactured by a growth technique such as MOVPE, MBE, and gas source MBE.

The third embodiment of the present invention will be described in detail with reference to the drawings. FIG. 6 is a sectional view of an avalanche multiplication type light receiving device according to an embodiment of the present invention. In the manufacturing process, the p-type InP buffer layer 13 is formed on the p-type InP substrate 12 by 0.5 μm, and the p-type InGaAs light absorption layer 14 is formed.
1.5 .mu.m, InAlAs400A (angstrom) / InGaAs200A 16-period heteroperiodic structure avalanche multiplication layer 15 of 1.0 .mu.m, and a cap layer 16 of 0.5 .mu.m are sequentially laminated. Here, In _x Ga that is a well layer (first layer) of the avalanche multiplication layer 15 is used.
The composition of the _1-x As layer was x = 0.458, and a tensile stress of 0.5% was applied. Further, In _y Al _{1 -y} As which is the barrier layer (second layer) of the avalanche multiplication layer
The composition of the layer was y = 0.447, and a tensile strain of 0.5% was applied.

Thereafter, to form the n ^-- type guard ring region 17, Si was added at 1 × 10 ¹³ c at an acceleration voltage of 100 kV.
m ^-2 , ion implantation up to a depth of 3000 A, 5 × 10
A concentration region of ¹⁶ cm ^-3 is obtained. Similarly, in order to form the n ⁺ light receiving region 18, 1 × 1 of Si is applied at an acceleration voltage of 200 kV.
^{0 1 4 cm -. 2,} 0 to ion implantation to a depth of 5 [mu] m,
A concentration region of 1 × 10 ¹⁸ cm ⁻³ is obtained. Further, a passivation film 8 of 1500 A is formed, and AuGe / Ni of 1500 A and TiPtAu of 50 are used as the n-side electrode 9.
0A is deposited. Further, the device structure shown in FIG. 4 is completed by depositing 1,500 A of AuZn as the p-side electrode 10.

The conduction band discontinuity energy (ΔEc) was increased and the ionization ratio was improved by the principle described in the operation under the above-described device structure. In addition, the transit time of holes in the barrier layer and the well layer was reduced and the pile-up of holes due to ΔEv was alleviated, resulting in a significant improvement in the band. As a result, the maximum bandwidth is 15 GHz and the GB product is 11
We have realized an avalanche multiplication type semiconductor light receiving element having 0 GHz, an ionization ratio (α / β) of 10, low noise with a quantum efficiency of 75%, and high-speed response characteristics. The device structure according to the present invention is specifically, MOVPE, MBE, gas source MB.
It can be produced by a growth technique such as E.

[0028]

In the semiconductor light receiving device according to the present invention, strain stress is applied to the well layer and the barrier layer of the hetero period avalanche multiplication layer to increase the conduction band discontinuity energy ΔEc and improve the ionization ratio. By reducing the valence band discontinuity energy ΔEv, the pile-up of holes is relaxed, or the mass of holes in the well layer and the barrier layer is reduced, and the transit time is reduced. As a result, it is possible to realize a semiconductor light receiving element having a wide band and high sensitivity and low noise characteristics.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a band structure of a light receiving element according to claim 1 of the present invention.

FIG. 2 is a diagram for explaining a band structure of a light receiving element of claim 2 according to the present invention.

FIG. 3 is a diagram for explaining a band structure of the light-receiving element according to claim 3 of the present invention.

FIG. 4 is a diagram for explaining a light receiving element according to an embodiment of claim 1 of the present invention.

FIG. 5 is a diagram for explaining a light receiving element according to an embodiment of claim 2 of the present invention.

FIG. 6 is a diagram for explaining a light receiving element of an embodiment of claim 3 of the present invention.

FIG. 7 is a structural diagram of a conventional APD.

[Explanation of symbols]

1 n-type InP substrate 2 n-type InP buffer layer 3 n-type InGaAs light absorption layer 4 n-type InP layer (avalanche multiplication layer) 5 n-type InP cap layer 6 p-type light receiving region 7 p-type guard ring region 8 passivation film 9 n-side ohmic electrode 10 p-side ohmic electrode 11 incident light 12 p-type InP substrate 13 p-type InP buffer layer 14 p-type InGaAs light absorption layer 15 p-type InAlAs / InGaAs hetero periodic structure avalanche multiplication layer 16 p-type InP cap layer 17 n type guard ring layer 18 n type light receiving region

Claims (3)

[Claims] 1. A semiconductor light-receiving device comprising a light absorption layer and a heteroperiodic structure avalanche multiplication semiconductor layer on a semiconductor substrate, wherein a group III atom of the first semiconductor layer constituting the heteroperiodic structure avalanche multiplication layer. When the average ionization energies of the group V and V atoms are E _A and E _B , and the average ionization energies of the group III and V atoms of the second semiconductor layer are E _C and E _D , respectively, E _A > E _C and A semiconductor light-receiving element characterized in that the relationship of E _B <E _D holds, and that the first semiconductor layer is loaded with tensile stress and the second semiconductor layer is loaded with compressive stress. 2. A group III atom of a first semiconductor layer constituting a heteroperiodic structure avalanche multiplication layer in a semiconductor light receiving device comprising a light absorption layer and a heteroperiodic structure avalanche multiplication semiconductor layer on a semiconductor substrate. When the average ionization energies of the group V and V atoms are E _A and E _B , and the average ionization energies of the group III and V atoms of the second semiconductor layer are E _C and E _D , respectively, E _A > E _C and holds the relationship of E _B <E _D, and a semiconductor light receiving element, characterized in that tensile stress in said first semiconductor layer to compressive stress and said second semiconductor layer is loaded. 3. A semiconductor light-receiving element comprising a light absorption layer and a heteroperiodic structure avalanche multiplication semiconductor layer on a semiconductor substrate, wherein a group III atom of the first semiconductor layer constituting the heteroperiodic structure avalanche multiplication layer. When the average ionization energies of the group V and V atoms are E _A and E _B , and the average ionization energies of the group III and V atoms of the second semiconductor layer are E _C and E _D , respectively, E _A > E _C and It holds the relationship of E _B <E _D, and a semiconductor light receiving element, characterized in that tensile stress in the stress and said second semiconductor layer tensile said first semiconductor layer is loaded.