JP3018589B2 - Semiconductor light receiving element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to optical communication, optical information processing,
The present invention relates to a semiconductor light receiving element used for 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 a wavelength band of 1 to 1.6 μm, an IP lattice-matched on an InP substrate has been used.
_{n 0. 5 3 Ga 0.} PIN -type semiconductor _{photodetector 47} As layer (hereinafter referred to as InGaAs layer) and a light absorbing layer (Electronics Letters (Electoronics
Letters) 1984, Volume 20, pp 653-
654), an avalanche multiplication type semiconductor light receiving element (IEEE Electron Device Letters (IEEE. Electron. Device. Let)
ters), 1986, Vol. 7, pp. 257-258). Particularly, the latter is practically used for long-distance communication because it has an internal gain effect and a high-speed response due to avalanche multiplication.

FIG. 8 is a structural diagram of a typical InGaAs-APD (the avalanche multiplication type semiconductor light receiving element is hereinafter referred to as an AP).
Abbreviated as D. ). The operating principle is that, among the optical carriers generated in the InGaAs light absorbing layer 3, hole carriers are injected into the InP avalanche layer 4 by an electric field. Since a high electric field is applied to the InP avalanche layer 4, ionization collision occurs, leading to multiplication characteristics. In this case, it is known that noise and high-speed response characteristics which are important in device characteristics are controlled by a random ionization process of carriers in a multiplication process. Specifically, the greater the difference between the electron and hole ionization rates of the InP layer, which is the multiplication layer, the greater the ionization rate ratio can be obtained (the electron and hole ionization rates are α and β, respectively).
Then, when α / β> 1, electrons should be the main carriers that cause ionization collision, and when β / α> 1, the holes should be. ), Desirable in device characteristics. However, the ionization rate ratio (α / β or β / α) is determined based on the material properties. In InP, β / α = 2 at most. This is significantly different from α / β = 20 of Si having low noise characteristics, and an innovative material technology is required to realize lower noise and higher speed response characteristics.

On the other hand, Capasso (F. Capass)
o) are the band discontinuous energies of the conduction band (伝 導 E _C )
Have been proposed for super-lattice APDs aiming at high sensitivity and wide band by increasing the ionization ratio α / β. An example is the Applied Physics Letters
rs), 1982, 40, p38.

On the other hand, it is known that the band structure is changed by applying a strain stress in the semiconductor superlattice structure, and that the degeneracy of the heavy hole band and the light hole band is particularly resolved in the valence band energy band. . An example is the Journal of Applied Physics (Journal of Applied Ph.
ysics), 1990, 67, p344.

[0006]

As described in the section of the prior art, in the superlattice APD, the value of the band discontinuity energy (△ E _C ) of the conduction band greatly contributes to the improvement of the ionization ratio. However, holes are piled up at the band discontinuity energy (△ E _V ) of the valence band,
The disadvantage that the band is suppressed also occurs at the same time.

An object of the present invention is to solve the above-mentioned problems and to provide an avalanche multiplication type semiconductor light receiving element having low noise and high speed response.

[0008]

[0009]

A semiconductor light receiving device according to the present invention.
In a semiconductor light receiving element having at least a light absorption layer and a hetero periodic structure avalanche multiplication semiconductor layer on a semiconductor substrate, a barrier layer constituting the hetero periodic structure semiconductor layer has an electron transmission preventing layer and a multiple quantum barrier. The average ionization energy of group III atoms in the barrier layer of the multiple quantum barrier formed of the region and having the electron transmission preventing layer and the two semiconductor layers is E _A , the forbidden band width is E _gA , and the avalanche multiplication layer is Assuming that the average ionization energy of the group III atoms of the well layer to be formed is E _B and the forbidden band width is E _gB , E _A <E _B and E _A + E _gA > E _B + E _gB hold, and the avalanche increase occurs. Tensile stress is applied to the double well layer, and the mass of holes is reduced.

[0010]

[0011]

FIG. 1 shows a band structure of a light receiving element according to claim 1 of the present invention. As a specific example which is composed of an avalanche multiplication layer hetero-periodic structure and satisfies the above-mentioned band structure, as an example, as the first semiconductor, In _x Ga _{1 -x} As (0 ≦ X ≦
1) In _y Al _{1 -y} As (0 ≦ y) in the second semiconductor layer
≦ 1). The traveling electron senses the discontinuous energy ΔE _C of the conduction band and can obtain the ionization energy corresponding to the energy, so that the α / β ratio can be increased. On the other hand, since a tensile stress is applied to the first semiconductor layer (well layer), the mass of holes traveling perpendicular to the layer direction is smaller than the mass of holes in the bulk crystal. (In this regard, Khao et al., In Journal of Applied Physics (J. Appl.
Phys. ) 57 (1985) p. 5428. As a result, the pile-up of holes due to the valence band energy difference ΔE _V is alleviated, so that a light-receiving element having a wide band and low noise can be obtained.

FIG. 2 shows a band structure of a second light receiving element according to the present invention. The avalanche multiplication layer has a hetero-periodic structure, and as a specific example satisfying the band structure of claim 2, as an example, the barrier layer constituting the avalanche multiplication layer has In
_x Al _{1 -x} As (0 ≦ x ≦ 1), In _y Ga
_1-y As (0 ≦ y ≦ 1) is used. The barrier layer having the hetero-periodic structure includes an InAlAs electron transmission preventing layer and In
It is composed of two regions of an AlAs / InGaAs multiple quantum barrier layer. As a result, the traveling electron senses the energy ΔE _MOB obtained by the multiple quantum barrier and the conduction band energy difference ΔE _C between InAlAs and InGaAs at a time, so that a large ionization energy can be obtained.

FIG. 3 shows a calculation example of the electron reflectivity at the multiple quantum barrier and the bulk interface. Electrons that have entered the multiquantum barrier feel a finite reflectance even when they have energy equal to or higher than the heterobarrier of the semiconductor forming the multiquantum barrier due to the interference effect. That is, the effective hetero barrier can be increased. FIG. 3 shows InAlA
It is an example of the calculation example of the multiple quantum barrier of s / InGaAs. From FIG. 3, it can be seen that the reflectivity of the electrons is 1.7, which is the value of the classical barrier.
It can be seen that it increases by a factor of two. In addition, since a tensile stress is applied to the well layer, the mass of holes traveling perpendicular to the layer direction is smaller than the mass of holes in the bulk crystal. Thereby, the pile-up of holes due to the valence band energy difference ΔE _V is alleviated, so that a light-receiving element having a wide band and low noise can be obtained.

The principle of operation is as shown in FIG.
Of the photocarriers generated in the As light absorption layer, only electron carriers are injected into the heterostructure avalanche multiplication layer by the reverse electric field. At this time, in the case of a normal superlattice APD, the injected electrons sense the discontinuous energy (ΔE _C ) of the conduction band of the hetero-periodic structure, and the ionization is promoted.
However, in an avalanche multiplication layer having a barrier layer with a multiple quantum barrier according to claim 2 of the present invention,
As described above, an effective increase in the hetero barrier ΔE _MOB can be obtained, so that a larger energy difference can be felt and the ionization rate can be promoted. Moreover, since the holes traveling in the valence band have a larger mass than the electrons, they do not feel the large quantum barrier, that is, can promote unilateral electron multiplication. On the other hand, since a tensile stress is applied to the well layer, the hole pyroup phenomenon at the valence band energy difference ΔE _V observed in a normal superlattice APD is alleviated.
Broadband characteristics can be obtained. As a result, an APD having a broadband low-noise characteristic can be obtained as compared with the conventional APD shown in FIG.

FIG. 4 is a view for explaining the band structure of the light receiving element according to claim 3 of the present invention. The left side shows (a) the case without strain, and the right side shows (b) the case where compressive stress is applied to the well layer of the present invention. The avalanche multiplication layer has a hetero-periodic structure, and as a specific example that satisfies the above-described band structure, as an example, the first semiconductor layer includes In _x Ga ₁ -xA.
s (0 ≦ x ≦ 1), and the second semiconductor layer has In _y Al _{1 -y}
As (0 ≦ y ≦ 1) is used. The traveling electron senses the discontinuous energy ΔE _C of the conduction band and can obtain the ionization energy corresponding to the energy.
β ratio can be increased. Here, the first semiconductor layer (well layer) and _{In 0. 6 1 Ga 0.} 3 9 As,
When a compressive stress of 0.5% is applied, the conduction band discontinuous energy ΔE _C is further increased by 39 meV as compared with the non-strain state. Thereby, the ionization ratio can be further increased. (Kao et al. Described this band change in the Journal Applied of Physics (J. of.
Appl. Phys. ) 57 (1985) p. 542
8, or Wang et al., Journal Applied Physics (J. of Appl. Phys.) 67
(1990) p. 344. ) In addition, In
When a compressive stress of 0.5% is applied to the GaAs well layer,
Since the composition shifts to In-rich, the hole mass is reduced by 1.4% as compared with the case of no distortion. As a result, the hole transit time in the well layer can be reduced, and the band of the APD can be improved.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first 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. As a manufacturing method, a p-type InP
The buffer layer 13 is 0.5 μm thick, the p-type InGaAs light absorbing layer 14 is 1.5 μm, and the 16-period hetero-periodic avalanche multiplication layer 15 of InAlAs500A (angstrom) / InGaAs250A is laminated 1.0 μm. Here, the well layer (first layer) of the avalanche multiplication layer
The composition of the In _x Ga _{1 -x} As layer is x = 0.33
And a tensile stress of 1.5% is applied. Thereafter, the cap layer 16 is sequentially laminated by 0.5 μm. Then, 100 k is formed to form the p ⁻ -type guard ring region 17.
1 × 10 ¹ to Si at an acceleration voltage of V ³ cm ^{- 2,} 3000
Ion implantation is performed to a depth of A to obtain a concentration region of 5 × 10 ¹⁶ cm ⁻³ . Similarly, to form the n ⁺ light receiving region 18,
Acceleration voltage 1 Si at × 10 of 200kV ^{1 4} cm ^{- 2,}
Ion implantation to a depth of 0.5 μm, 1 × 10 ¹⁸ cm
^-Get a density range of ³ . Further, a passivation film 8 is formed at 1500 A, and AuGe / Ni is used as an n-side electrode 9.
Is deposited at 1500 A, and TiPtAu is deposited at 500 A. Further, the element structure of FIG. 5 is completed by depositing 1500 nm of AuZn as the p-side electrode 10.

Under the above-described device structure, the ionization of electrons is exaggerated by the principle described in the operation, the effective ionization rate ratio (α / β ratio) is 50, the maximum band is 8 GHz, and the quantum efficiency is as low as 80%. We have realized an avalanche multiplication semiconductor photodetector with noise and high-speed response characteristics. Specifically, the semiconductor structure of the device according to the present invention can be manufactured by a growth technique such as MOVPE, MBE, or gas source MBE.

A second embodiment of the present invention will be described in detail with reference to the drawings. FIG. 6A is a sectional view of an avalanche multiplication type light receiving element according to an embodiment of the present invention. As a manufacturing method, a p-type InP buffer layer 13 having a thickness of 0.5 μm, a p-type InGaAs light absorbing layer 14 having a thickness of 1.5 μm, and an InAlAs
The avalanche multiplication layer 20 of 16-period hetero-periodic structure of 500 A / InGaAs 250 A is laminated by 1.0 μm. Here, In _x G, which is a well layer of the avalanche multiplication layer, is used.
The composition of a ₁ -xAs is x = 0.33, and the InAlAs layer serving as a barrier layer includes a multiple quantum barrier.
The structure of the barrier layer of the avalanche multiplication layer includes an electron transmission preventing layer 21 and a multiple quantum barrier layer 22, and the band diagram of this structure is shown in FIG. The electron transmission preventing layer is 10
The 0A InAlAs layer and the multiple quantum barrier layer are made of InAlA.
It is composed of five layers of s30A / InGaAs20A. After that, a p-type InP cap layer 16 is sequentially laminated by 0.5 μm.

After that, to form the n ⁻ -type guard ring region 17, Si is applied at 1 × 10 ¹³ c at an acceleration voltage of 100 kV.
m ^-2 , ion implantation to a depth of 3000A, 5 × 10
A density region of ¹⁶ cm ^-3 is obtained. Similarly, in order to form the n ⁺ light receiving region 18, 1 × 1 Si is applied at an acceleration voltage of 200 kV.
0 ^{1 4} cm ^{- 2,} and ion implantation to a depth of 0.5 [mu] m,
A concentration region of 1 × 10 ¹⁸ cm ⁻³ is obtained. Further, a passivation film 8 is formed at 1500A, and as an n-side electrode 9, AuGe / Ni is 1500A and TiPtAu is 50A.
0A is deposited. 6A is completed by depositing 1500 nm of AuZn as the p-type electrode 10.

Under the above-described device structure, the electron ionization is exaggerated by the principle described in the operation, the effective ionization rate ratio (α / β ratio) is 110, the maximum band is 8 GHz, and the quantum efficiency is 80%. An avalanche multiplication type semiconductor photodetector with high-speed response characteristics has been realized. Specifically, the semiconductor structure of the device according to the present invention can be manufactured by a growth technique such as MOVPE, MBE, or gas source MBE.

A third embodiment of the present invention will be described in detail with reference to the drawings. FIG. 7 is a sectional view of an avalanche multiplication type light receiving element according to an embodiment of the present invention. As a manufacturing method, a p-type InP
The buffer layer 13 is 0.5 μm, the p-type InGaAs light absorbing layer 14 is 1.5 μm, and InAlAs (In composition ratio 0.5
2) 400A (Angstrom) / InGaAs20
Avalanche multiplication layer 15 with 16-period hetero-periodic structure of 0A
Are laminated by 1.0 μm. Here, In _x Ga _{1 -x} A, which is a well layer (first semiconductor layer) of the avalanche multiplication layer.
The composition of the s layer is x = 0.61, and a compressive stress of 0.5% is applied. After that, the cap layer 16 is
m are sequentially laminated. Thereafter, the n ⁻ -type guard link area 17
For the formation, 1 × 10 Si was applied at an acceleration voltage of 100 kV.
^{1 3} cm ^{- 2,} and ion implantation to a depth of 3000A, 5
A concentration region of × 10 ¹⁶ cm ⁻³ is obtained. Similarly, for the n ⁺ light receiving region 18 formed, 1 × the Si at an acceleration voltage of 200kV 10 ^{1 4} cm ^{- 2,} and ion implantation to a depth of ^{0.5μm, 1 × 10 1 8 cm} - the density region ³ obtain. Furthermore,
A passivation film 8 is formed at 1500 A, and an n-side electrode 9 is formed.
Then, AuGe / Ni is deposited at 1500 A and TiPtAu is deposited at 500 A. AuZ is used as the p-side electrode 10.
By depositing n at 1500 A, the device structure of FIG. 7 is completed.

Under the above-described element structure, the ionization of electrons is exaggerated by the principle described in the operation, the effective ionization ratio (α / β ratio) 45, the hole transit time is shortened, and the maximum band is reduced. 12GHz, low noise of 75% quantum efficiency,
An avalanche multiplication type semiconductor photodetector with high-speed response characteristics has been realized. Specifically, the semiconductor structure of the device according to the present invention can be manufactured by a growth technique such as MOVPE, MBE, or gas source MBE.

[0023]

According to the semiconductor light receiving device of the present invention, the band at the time of multiplication can be improved by reducing the mass of holes in the well layer. Further, according to the second aspect of the present invention, since the barrier layer of the hetero-periodic avalanche multiplication layer includes a multiple quantum barrier layer, the effective conduction band energy difference can be increased, and the ionization rate ratio can be further increased. As described above, a semiconductor light receiving element having a wide band, high sensitivity and low noise characteristics can be realized.

[Brief description of the drawings]

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

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

FIG. 3 is a diagram illustrating a calculation example in the case of an InAlAs / InGaAs multiple quantum well.

FIG. 4 is a diagram for explaining a band structure of a light receiving element according to the present invention.

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

FIG. 6 is a diagram for explaining a light receiving element according to a second embodiment of the present invention.

FIG. 7 is a diagram for explaining a light receiving element according to a third embodiment of the present invention.

FIG. 8 is a structural diagram of a conventional APD.

[Explanation of symbols]

Reference Signs List 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 heterocyclic periodic structure avalanche multiplication layer 16 p-type InP cap layer 17 n-type guard ring layer 18 n-type light receiving region 20 InAlAs / InGa including p-type multiple quantum barrier
As hetero periodic structure avalanche multiplication layer 21 InAlAs electron transmission preventing layer 22 InAlAs / InGaAs multiple quantum barrier layer

Claims (1)

(57) [Claims] 1. A semiconductor light receiving device comprising at least a light absorption layer and a hetero periodic structure avalanche multiplication semiconductor layer on a semiconductor substrate, wherein the barrier layer forming the hetero periodic structure semiconductor layer comprises an electron transmission preventing layer and a multiple quantum well. Barrier 2
The average ionization energy of group III atoms in the barrier layer of the multiple quantum barrier formed of the region and having the electron transmission preventing layer and the two semiconductor layers is E _A , the forbidden band width is E _gA , and the avalanche multiplication layer is Assuming that the average ionization energy of the group III atoms of the well layer to be formed is E _B and the forbidden band width is E _gB , E _A <E _B and E _A + E _gA > E _B + E _gB hold, and the avalanche increase occurs. A semiconductor photodetector, wherein a tensile stress is applied to a double well layer to reduce the mass of holes.