JPH09181390A - Semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high performance compound semiconductor device by providing a conductive n-type single or multiple semiconductor layer doped more heavily than a second p-type semiconductor layer between the second semiconductor layer and an active layer. SOLUTION: The periphery of an active layer comprises an n-InP substrate 20, an undoped active layer 21 of emission wavelength 1.5μm, a P-type Zn doped InP layer 22, an Fe doped semiinsulating InP current constriction layer 23, and an n-type SiInGaAsP four element mixed crystal layer 24 (composition wavelength 1.1μm). Zn and Si are doped, respectively, by 1×10<18> /cm<3> and 1.5×10<18> /cm<3> and conventional diffusion of Zn into the active layer 21 can not be observed on the concentration distribution curve of Zn. Since an n-type doping layer 24 (1.5×10<18> /cm<3> ) is inserted between a P-type Zn doping layer 22 and an undoped active layer 21, diffusion of Zn into the active layer is suppressed and a high performance device can be fabricated with high yield.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compound semiconductor device having a semi-insulating compound semiconductor current confinement layer and good characteristics.

[0002]

2. Description of the Related Art In a compound semiconductor device, a semi-insulating current constriction structure reduces the device capacitance and is therefore essential for obtaining high speed device characteristics. However, in the conventional structure, the dopant in the semi-insulating current confinement layer (for example, Fe) and the dopant in the p-type doping layer near the active layer (for example, p of Zn or the like) are used.
The quality of the active layer deteriorates due to the mutual diffusion of (type impurities). FIG. 1 is a view for explaining the quality deterioration mechanism of the active layer due to the above-mentioned mutual diffusion in the conventional structure, and is a cross-sectional view of the periphery of the active layer of the optical element structure having the semi-insulating current confinement layer (away from the active layer such as the contact layer). The parts are not shown). 10 is an n-InP substrate, 11 is an undoped InGaAsP active layer, 12 is p-type (Zn) -doped InP, 13 is Fe-doped semi-insulating InP current constriction layer,
14 is Fe, 15 is Zn, 16 is the Zn doping distribution in the vicinity of the active layer estimated from the doping conditions during crystal growth, and 17 is the actual Z obtained by SIMS measurement.
It is a concentration distribution of n.

In this structure, the semi-insulating current confinement layer 1
Dopan Fe14 of No. 3 and the p-type doping layer dopant Zn15 in the p-type doping layer cause mutual diffusion, and Zn in the interstitial position increases. That is, Fe in the semi-insulating layer
14 diffuses into the p-type doping layer and occupies the lattice position, and as a result, the Zn15 at the lattice position moves to the interstitial position. Subsequently, Zn15 moved to the interstitial position diffused into the active layer 11 and deteriorated the quality of the active layer. In order to improve the performance of the device, a high quality active layer is required. However, if there is diffusion of impurities into the active layer as described above,
It has become a problem because it becomes impossible to manufacture a device having a performance as intended, which directly leads to performance deterioration, reliability deterioration, and yield reduction of the device.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to solve these problems and provide a high performance compound semiconductor device.

[0005]

According to the present invention, there is provided a semiconductor device comprising:
It is characterized in that it has a layer which is n-type doped at a concentration higher than the carrier concentration of the p-type doping layer between the p-type doping layer and the undoped active layer. In other words, the present invention relates to a first semiconductor layer having an n-type conductivity type and a semiconductor single layer or quantum layer having a lowest transition energy between the conduction band and the valence band smaller than that of the first semiconductor layer. A laminated structure comprising an active layer including a light emitting layer formed of a well, and a second semiconductor layer having a p-type conductivity type having a lowest transition energy between the conduction band and the valence band higher than that of the light emitting layer, In a semiconductor device in which a mesa structure having a laminated structure is embedded with a semi-insulating semiconductor, a conductivity type is n-type and an n-type impurity concentration is the second semiconductor layer between the second semiconductor layer and the active layer. The present invention is characterized by having a semiconductor single layer or a semiconductor laminated layer having a p-type impurity concentration higher than the above.

That is, Fe or C due to current confinement
Using a semi-insulating compound semiconductor such as InP doped with r or the like or InP doped with Fe and Ti at the same time, p
In a compound semiconductor device having an undoped (undoped) active layer between a p-type doped layer and an n-type doped layer, the carrier concentration of the p-type doped layer on the undoped active layer side of the boundary between the p-type doped layer and the undoped active layer Insert the n-type doping layer at the above concentration, or insert the n-type doping layer at a portion of the boundary on the p-type doping layer side.
By performing the type doping, deterioration of the active layer due to diffusion of a doping impurity of a semi-insulating semiconductor such as Fe or Cr or an impurity such as a p-type impurity such as Zn is suppressed.

In the conventional device structure, the p-type doping layer is adjacent to the undoped active layer, and the n-type doping is p-type.
It is not applied between the type doping layer and the active layer, which is different from the device structure according to the present invention. In addition, in the conventional device structure, for the purpose of reducing the threshold current density by improving the injection of carriers into the active layer, an n-type layer having a carrier concentration higher than that of the p-type doping layer is formed around the barrier layer in the active layer and the multiple quantum structure. Doping (1 × 10 ¹⁸ / cm ³ , 1 ×
10 ¹⁹ / cm ³ or less) is also available. (Abe et al .: 1
1994, 41st Spring Biological Society, 30p-K-4).
This structure has an undoped layer between a p-type doped layer and an n-type doped layer. That is, p-type doping layer and n
The type doping layers are not adjacent, which is different from the structure according to the present invention.

In this structure, since the active layer, that is, the light emitting layer is doped at a high concentration, there is a drawback that free carrier absorption loss becomes large and resonator loss increases.
Therefore, there is a concern about an increase in the oscillation threshold value due to an increase in resonator loss. Further, since it is impossible to apply an electric field when the light emitting layer is doped, the light emitting element is used as an electric field control element (for example, when an electric field is applied to a multi-weight well to be used as a saturable absorber). Therefore, it becomes difficult to integrate the light emitting layer and the electric field control element on the same substrate.

According to the present invention, since Dopan Fe or Cr of the semi-insulating current confinement layer diffuses into the p-type doping layer and occupies the lattice position, the p-type doping diffused from the lattice position to the interstitial position. In the n-type doping layer, p-type impurities such as the layer dopant Zn combine with the n-type dopant (Si or the like) to form a complex (Zn-Si or the like), which makes it difficult to diffuse. Therefore, in order to suppress the diffusion of all the p-type impurities such as Zn, an n-type impurity such as Si having a concentration higher than the carrier concentration of the p-type doping layer is required (for example, C. Blaauw et al .: Journal of Electroni
c Materials, Vol.21, No.2, (1991) p.173). Therefore,
Diffusion of p-type impurities such as p-type dopant Zn into the active layer is suppressed by the n-type doping layer having a concentration of carrier concentration of p-type impurities between the p-type doping layer / active layer. That is, diffusion of p-type impurities such as the p-type dopant Zn into the active layer is prevented, so that deterioration of the quality of the active layer can be suppressed. Further, since it is not necessary to dope the main part of the light emitting layer, problems such as increase of resonator loss due to free carrier absorption and difficulty of integration of the electric field control element do not occur.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the first semiconductor layer having an n-type conductivity type and the lowest transition energy between the conduction band and the valence band are smaller than those of the first semiconductor layer. A stack of an active layer including a semiconductor single layer or a light emitting layer formed of a quantum well, and a second semiconductor layer having a p-type conductivity with the lowest transition energy between the conduction band and the valence band being larger than that of the light emitting layer. In a semiconductor device having a structure, in which a mesa structure having the laminated structure is embedded with a semi-insulating semiconductor, a conductivity type is n-type and an n-type impurity concentration is between the second semiconductor layer and the active layer. A semiconductor device having a semiconductor single layer or a semiconductor stack having a p-type impurity concentration higher than that of the second semiconductor layer.

[0011]

【Example】

(Embodiment 1) FIG. 2 is a view for explaining the first embodiment of the present invention, and is a cross-sectional view of the periphery of an active layer of an optical semiconductor element (a portion such as a contact layer apart from the active layer is not shown). Indicates. 20 is an n-InP substrate, 21 is an emission wavelength of 1.5 μm.
m is an undoped active layer, 22 is p-type (Zn) -doped InP, 23 is Fe-doped semi-insulating InP current confinement layer, 24 is n-type (Si) -doped InGaAsP quaternary mixed crystal layer (composition wavelength 1.1 μm, layer Thickness 10 nm), 25 is the doping distribution of the p-type dopant Zn estimated from the doping conditions during crystal growth, and 26 is the n-type dopant Si.
The doping distribution of is shown. 27 is the actual Zn concentration distribution obtained by SIMS measurement. The active layer 21 is In
GaAsP quaternary mixed crystal layer (composition wavelength 1.1 μm, layer thickness 10
0 nm), 6 layers of InGaAsP quaternary mixed crystal quantum well layer (layer thickness 60 nm), 5 layers of InGaAsP quaternary mixed crystal barrier layer (composition wavelength 1.1 μm, layer thickness 20 nm), InGaA
sP quaternary mixed crystal layer (composition wavelength 1.1 μm, layer thickness 100 n
m). Zn doping concentration is 1 × 10 ¹⁸ / c
The doping concentration of m ³ and Si is 1.5 × 10 ¹⁸ / cm ³
It is. From the Zn concentration distribution 27, the diffusion of Zn into the active layer 21 observed in the conventional structure is not observed in the structure according to the present invention. As described above, the n-type (Si) doping layer (1.5 × 1) is formed between the p-type doping layer and the undoped active layer.
It is understood that the diffusion of Zn into the active layer is suppressed by inserting 0 ¹⁸ / cm ³ ).

FIG. 3 shows the current / light output characteristics of a 1.5 μm band semiconductor laser having the Fe-doped current confinement layer having the above structure. Reference numeral 31 indicates the conventional structure (broken line), and 32 indicates the present invention (solid line). Is. With the conventional structure, the quality of the active layer is deteriorated due to the diffusion of Zn into the active layer, which causes an increase in threshold current and a decrease in efficiency. On the other hand, in the structure according to the present invention, diffusion of Zn into the active layer is suppressed and the quality of the active layer is maintained, so that improvement in device characteristics (reduction in threshold current, improvement in efficiency) is achieved.

FIG. 4 shows changes in the optical absorption spectrum of the optical modulator having the above structure due to the application of an electric field. Reference numeral 41 is a conventional structure (dotted line), and 42 is according to the present invention (solid line).
In the spectrum in the conventional structure, the wavelength shift at the absorption edge due to the application of the electric field is not observed because the quality of the active layer deteriorates due to the diffusion of Zn into the active layer. On the other hand, in the spectrum of the structure according to the present invention, since the diffusion of Zn into the active layer is prevented and the quality of the active layer is maintained, the wavelength shift of the absorption edge due to the application of the electric field is observed.

FIG. 5 is a diagram for explaining the second embodiment of the present invention, showing a cross-sectional view of the periphery of the active layer of an optical semiconductor device (a portion such as a contact layer apart from the active layer is not shown). . 50 is an n-InP substrate, 51 is an emission wavelength of 1.5 μm.
m is an undoped active layer, 52 is p-type (Zn) -doped InP, 53 is Fe-doped semi-insulating InP current confinement layer, 54 is n-type (Si) -doped InP (layer thickness 3n).
m) and an InGaAsP quaternary mixed crystal layer (composition wavelength: 1.1)
μm, layer thickness 7 nm), 55 shows the doping distribution of the p-type dopant Zn (dotted line) estimated from the doping conditions during crystal growth, and 56 shows the doping distribution of the n-type dopant Si (solid line). 57 is the actual Zn concentration distribution obtained by SIMS measurement. The active layer 51 is InGaAs
P quaternary mixed crystal layer (composition wavelength 1.1 μm, layer thickness 100 n
m), 6 layers of InGaAsP quaternary mixed crystal quantum well layer (layer thickness 60 nm), 5 layers of InGaAsP quaternary mixed crystal barrier layer (composition wavelength 1.1 μm, layer thickness 20 nm), InGaAsP quaternary mixed crystal layer (composition) The wavelength is 1.1 μm and the layer thickness is 100 nm). Zn doping concentration is 1 × 10 ¹⁸ / cm ³ , S
The doping concentration of i is 1.5 × 10 ¹⁸ / cm ³ .
As can be seen from 55 and 56, the n-type doping between the p-type doping layer / active layer is p-type (Zn) doping InP.
The region of 3 nm on the side is applied to the region of 7 nm on the side of the InGaAsP quaternary mixed crystal layer (composition wavelength: 1.1 μm). From the Zn concentration distribution 57, the diffusion of Zn into the active layer 51 observed in the conventional structure is not observed in the structure according to the present invention. As described above, an n-type (Si) doping layer (1.5 × 10 ¹⁸ / cm ³ ) is formed between the p-type doping layer and the undoped active layer.
It is understood that the diffusion of Zn into the active layer is suppressed by inserting the. In the structure according to this embodiment, the effect obtained in the first embodiment can be obtained.

FIG. 6 is a diagram for explaining the third embodiment of the present invention, showing a cross-sectional view of the periphery of the active layer of an optical semiconductor element (a portion such as a contact layer apart from the active layer is not shown). . 60 is an n-InP substrate, 61 is an emission wavelength of 1.5 μm.
m is an undoped active layer, 62 is p-type (Zn) -doped InP, 63 is Fe-doped semi-insulating InP current confinement layer, 64 is n-type (Si) -doped p-type doped InP (layer thickness 10 nm), Reference numeral 65 shows a doping distribution of the p-type dopant Zn (dotted line) estimated from the doping conditions during crystal growth, and 66 shows a doping distribution of the n-type dopant Si (solid line). 67 is an actual Zn concentration distribution obtained by SIMS measurement. The active layer 61 is I
nGaAsP quaternary mixed crystal layer (composition wavelength 1.1 μm, layer thickness 1
00 nm), 6 layers of InGaAsP quaternary mixed crystal quantum well layer (layer thickness 60 nm), 5 layers of InGaAsP quaternary mixed crystal barrier layer (composition wavelength 1.1 μm, layer thickness 20 nm), InGaA
sP quaternary mixed crystal layer (composition wavelength 1.1 μm, layer thickness 100 n
m). Zn doping concentration is 1 × 10 ¹⁸ / c
The doping concentration of m ³ and Si is 1.5 × 10 ¹⁸ / cm ³
It is. As can be seen from the Si doping distribution 66,
n-type doping is p-type doping InP62 / active layer 6
It is applied to the region on the p-type doping InP 62 side of the 1 boundary. In this case, the electrical properties of this region are p-type due to charge compensation between the p-type dopant Zn and the n-type dopant Si.
Type or n type shows a carrier concentration of 1 × 10 ¹⁶ / cm ³ or less, but since it is a thin region of 10 nm, it does not significantly affect the device characteristics. From the Zn concentration distribution 67, the diffusion of Zn into the active layer 61 observed in the conventional structure is not observed in the structure according to the present invention. As described above, the diffusion of Zn into the active layer is suppressed by inserting the n-type (Si) doping layer (1.5 × 10 ¹⁸ / cm ³ ) between the p-type doping layer and the undoped active layer. I understand.
In the structure according to this embodiment, the effect obtained in the first embodiment can be obtained.

Although the present embodiment has been described in the case of the wavelength band of 1.5 μm, an element structure having another wavelength band of 1.3 μm or the like is also possible. The active layer has a multi-quantum well structure having six well layers and five barrier layers, but the number of well layers and barrier layers is not limited, and the double hetero structure does not have a multi-quantum structure. (For example, the active layer may be a double heterostructure composed of a single composition InGaAsP quaternary mixed crystal layer). In addition, InP and InGaA, which are III-V group compound semiconductors, are used as compound semiconductors.
As described in the case of sP, other III-V group compound semiconductors such as GaAs, InGaAs, AlAs, and AlGa.
II-VI such as As, AlInGaAs, AlGaInP, etc.
It is also possible in the case of ZnS, CdSe, ZnSSe, etc., which are group compound semiconductors. In addition to Zn for the p-type impurities, Cd, Mg, Be, C, etc., and Si for the n-type impurities.
The same effect can be obtained by using Sn, S, Se or the like.
In addition to the Fe-doped semi-insulating compound semiconductor, Cr
It may be doped or simultaneously doped with Ti and Fe.

[0017]

As described above, by using the device structure according to the present invention, a high-quality active layer that is not affected by the diffusion of impurities can be obtained, so that a high-performance device can be manufactured with a high yield. .

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a quality deterioration mechanism of an active layer due to the above-mentioned mutual diffusion in a conventional structure, and shows an optical element structure having a semi-insulating current confining layer.

FIG. 2 is a diagram for explaining the first embodiment of the present invention, showing a cross-sectional view of the periphery of an active layer of an optical semiconductor element (a portion such as a contact layer apart from the active layer is not shown).

3A and 3B show current / light output characteristics of a 1.5 μm band semiconductor laser having an Fe-doped current confinement layer having the above structure, where 31 is the conventional structure (dotted line) and 32 is the present invention (solid line). .

FIG. 4 shows an optical absorption spectrum of the optical modulator having the above structure. 41 is a conventional structure and 42 is according to the present invention.

FIG. 5 is a diagram illustrating a second embodiment of the present invention,
A cross-sectional view of the periphery of the active layer of the optical semiconductor element (a portion away from the active layer such as a contact layer is not shown) is shown.

FIG. 6 is a diagram illustrating a third embodiment of the present invention,
A cross-sectional view of the periphery of the active layer of the optical semiconductor element (a portion away from the active layer such as a contact layer is not shown) is shown.

[Explanation of symbols]

10 n-InP substrate 11 undoped InGaAsP active layer 12 p-type (Zn) -doped InP 13 Fe-doped semi-insulating InP current confinement layer 14 Fe 15 Zn 16 Zn doping distribution in the vicinity of the active layer estimated from doping conditions during crystal growth 17 Actual Zn concentration distribution obtained by SIMS measurement 20 n-InP substrate 21 Undoped active layer that is 1.5 μm from emission wavelength 22 p-type (Zn) -doped InP 23 Fe-doped semi-insulating InP current confinement layer 24 n-type (Si) -doped InGaAsP quaternary mixed crystal layer (composition wavelength: 1.1 μm, layer thickness: 10 nm) 25 p estimated from doping conditions during crystal growth
Doping Distribution of Type Dopant Zn 26 shows the doping distribution of n-type dopant Si.
27 is an actual Zn concentration distribution obtained by SIMS measurement 50 n-InP substrate 51 Undoped active layer with an emission wavelength of 1.5 μm 52 p-type (Zn) -doped InP 53 Fe-doped semi-insulating InP current confinement layer 54 n Type (Si) doping InP (layer thickness 3 nm)
And InGaAsP quaternary mixed crystal layer (composition wavelength: 1.1μ
m, layer thickness 7 nm) 55 p estimated from doping conditions during crystal growth
Type dopant Zn doping distribution (dotted line) 56 n-type dopant Si doping distribution (solid line) 57 actual Zn concentration distribution obtained by SIMS measurement 60 n-InP substrate 61 undoped active layer with emission wavelength of 1.5 μm 62 p-type (Zn) -doped InP 63 Fe-doped semi-insulating InP current confinement layer 64 n-type (Si) -doped p-type doped InP (layer thickness 10 nm) 65 p estimated from doping conditions during crystal growth
Type dopant Zn doping distribution (dotted line) 66 n-type dopant Si doping distribution (solid line) 67 Actual Zn concentration distribution obtained by SIMS measurement

Claims (1)

[Claims] 1. A first semiconductor layer having an n-type conductivity type, and a semiconductor single layer or quantum well having a lowest transition energy between a conduction band and a valence band smaller than that of the first semiconductor layer. And a second semiconductor layer having a p-type conductivity type having a lowest transition energy between the conduction band and the valence band which is higher than that of the light emitting layer. In a semiconductor device in which a mesa structure having a structure is embedded with a semi-insulating semiconductor, a conductivity type is n-type and an n-type impurity concentration of the second semiconductor layer is between the second semiconductor layer and the active layer. A semiconductor device having a semiconductor single layer or a semiconductor stacked layer having a p-type impurity concentration higher than that.