JPH08116132A - Semiconductor light-emitting element and its manufacture - Google Patents

Abstract

PURPOSE: To provide a ZnSe-based semiconductor light-emitting element whose characteristic is good. CONSTITUTION: Guide layers 4, 6 for a semiconductor light-emitting element provided with a separated light confinement hetero-structure are formed of Zn1-a Caa Sb Se1-b (where 0<=a<=1, 0<=b<=1, 0<=x<=1 and 0<=y<=1). An active layer 5 is formed of a Zn1-x Cdx Sy Se1-y single layer (where 0<=x<=1, 0<=y<=1, a<x and y<b). Thereby, the band offset of a valence band becomes larger than that in conventional cases, holes are confined with good efficiency, and it is possible to realize a laser whose threshold current is larger than that in conventional cases.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light emitting device and a method for manufacturing the same, and more particularly, to an I formed on a GaAs substrate.
The present invention relates to a group I-VI compound semiconductor laser and a method for manufacturing the same.

[0002]

2. Description of the Related Art As a key device for the next-generation high-density information processing technology, a semiconductor light emitting device using a II-VI group compound semiconductor has attracted attention. The II-VI group compound semiconductor makes it possible to shorten the wavelength of the laser. As a semiconductor light emitting device in which a II-VI group compound semiconductor laminated structure is formed on a GaAs substrate, one having a separate confinement hetero type quantum well structure as shown in FIG. 12 is known.

According to the structure of FIG. 12, ZnS _0.07 Se _0.93 and Zn _1-x Mg _x S _y S lattice-matched to the GaAs substrate are used.
e _1−y is used as the material for the guide layer and the cladding layer, respectively. As a result, not only crystal defects in the light emitting device can be reduced, but also a band offset between the active layer and the guide layer and a refractive index difference between the guide layer and the clad layer can be increased. . By doing so, both carriers and light can be efficiently confined. By adopting such a structure, continuous operation at room temperature of a laser having a wavelength in the 500 nm band has been successful (N. Nakayama et.al .; Electronics Lett. 2).
9 (1993) 1488, A. Salokative et.al .; Electronics Lett.
29 (1993) 2192).

[0004]

The inventor of the present invention has been described in FIG.
When ZnS _0.07 Se _0.93 is used as the material for the guide layer of the separate confinement heterostructure shown in (1), the following problems have been found. The problems are as follows.

With respect to the structure of FIG. 12, the band offsets of the conduction band and the valence band are determined by the common anion rule and the common cation rule (Kunio Ichino et al. "Design and Fabrication of II-VI Group Semiconductor Heterostructures", Applied Physics Vol. No. (1992) p.11
7) was used. The band offset of the valence band between the active layer 71 and the guide layer 70 or 72 is shown in FIG.
As shown in (a), it becomes as small as 87 meV. Conventionally, it has been considered that a band offset of about 87 meV is sufficient for the valence band. However, the inventor of the present application cannot efficiently confine holes in the active layer when the band offset of the valence band becomes as small as 87 meV, so that the laser oscillation threshold current density is 600 to 110.
We have found a problem that the life of the device is shortened by the increase of 0 A / cm ² .

Further, when the semiconductor layer shown in FIG. 12 is grown, the composition of Zn, S and Se in each semiconductor layer is different for each layer, so the growth is interrupted and the temperature and pressure of the material are changed. There is also a problem that a plurality of the same materials must be prepared in accordance with the composition of each layer, or the material must be changed so as to match the composition.

In the former method, the growth must be interrupted during the time required to change the temperature and pressure of the material when forming each layer. Due to the influence of this growth interruption, each layer interface may be deteriorated and the characteristics may be deteriorated. In the latter method, the number of materials used becomes large, the crystal growth apparatus becomes very complicated, the time required for maintenance such as use of the apparatus and material replacement, and the cost of the completed light emitting element is large. Become.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a semiconductor light emitting element having a threshold current density smaller than that of a conventional one, a long service life, and a highly reliable semiconductor light emitting element. It is to provide a manufacturing method.

Another object of the present invention is to provide a semiconductor light emitting device capable of forming an active layer and a guide layer without interruption of an epitaxial growth process, and a method of manufacturing the same.

[0010]

A semiconductor light emitting device of the present invention comprises a GaAs substrate and an I formed on the GaAs substrate.
A semiconductor light emitting device having a Group I-VI compound semiconductor laminated structure, the semiconductor laminated structure including a ZnCdSSe active layer and a pair of ZnCdSSe guide layers sandwiching the active layer. The composition of Cd is larger than the composition of Cd in the guide layer, and the composition of S in the active layer is smaller than the composition of S in the guide layer, whereby the above object is achieved.

The laminated structure includes a pair of II-VI compound semiconductor clad layers sandwiching the active layer and the guide layer, and the active layer, the guide layer and the clad layer form a separated optical confinement hetero structure. Is forming.

At least one of the pair of guide layers is
(Zn _1-x Cd _x Se) _m (ZnS _y Se _{1 -y} ) _n superlattice, and the active layer comprises Zn _1-x constituting the superlattice.
Cd _x Se or Zn _1-x Cd _x Se and Zn _1-u Cd _u S _v S
e _1−v (0 <u <1, 0 <v <1, x <u, y <v).

At least one of the pair of guide layers is
Each layer consists of binary crystal (ZnSe) _m (CdSe)
_It may be formed from an _n (ZnS) _l (m, n and l are integers) superlattice.

At least one of the pair of guide layers is
(Zn _1-a Cd _a S _b Se _1-b ) _m (Zn _1-c Cd _c S _d Se
_1-d ) _n superlattice (0≤c≤1, 0≤d≤1, (am + b
n) / (m + n) <x, y <(cm + dn) / (m +
n), m, and n are integers).

The active layer is formed of (Zn _1-x Cd _x S _y S
e _1-y ) _m (Zn _1-z Cd _{z St} Se _1-t ) _n superlattice (0 ≦ x
≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1, 0 ≦ t ≦ 1, a <(x
m + yn) / (m + n), (zm + tn) / (m + n)
<B, m, and n are integers).

The active layer is formed of (Zn _1-a Cd _a S _b S
e _1-b ) _m (Zn _1-c Cd _{c Sd} Se _1-d ) _n superlattice, and at least one of the pair of guide layers comprises (Zn 1
_1-x Cd _{x Sy} Se _1-y ) _k (Zn _1-z Cd _{z St} Se _1-t )
_l (m, n, k, l are integers, 0 ≦ z ≦ 1, 0 ≦ t ≦ 1,
(Xk + yl) / (k + l) <(am + bn) / (m +
n), (cm + dn) / (m + n) <(zk + tl) /
(K + 1)).

The method of manufacturing a semiconductor light emitting device according to the present invention is
aAs substrate and II-V formed on the GaAs substrate
A group I compound semiconductor laminated structure, the semiconductor laminated structure includes a ZnCdSSe active layer and a pair of ZnCdSSe guide layers sandwiching the active layer, and Cd in the active layer.
A method for manufacturing a semiconductor light emitting device, wherein the composition of Cd is larger than the composition of Cd in the guide layer and the composition of S in the active layer is smaller than the composition of S in the guide layer, and the source of Cd is provided. As a result, the molecular beam epitaxial growth step of forming the guide layer or the active layer by using only one cell of Cd alone or a compound containing the same is included, thereby achieving the above object.

In the molecular beam epitaxial growth step, the guide layer and the active layer may be formed without changing the molecular beam intensity of the only cell.

Another method of manufacturing a semiconductor light emitting device according to the present invention is a GaAs substrate and an I formed on the GaAs substrate.
I-VI group compound semiconductor laminated structure, the semiconductor laminated structure includes a ZnCdSSe active layer and a pair of ZnCdSSe guide layers sandwiching the active layer, and the composition of Cd in the active layer is in the guide layer. Which is larger than the composition of Cd in the active layer and smaller in composition of S in the active layer than the composition of S in the guide layer.
The only source of S as a source of S or a compound containing it
The method includes a molecular beam epitaxial growth step of forming the guide layer or the active layer by using one cell, thereby achieving the above object.

In the molecular beam epitaxial growth step, the guide layer and the active layer may be formed without changing the molecular beam intensity of the only cell.

[0021]

In the present invention, ZnCdSS is used for the active layer and the guide layer.
e is used. Moreover, the composition of Cd of the active layer is set to be larger than that of Cd of the guide layer, and the composition of S of the active layer is set to be smaller than that of S of the guide layer. As a result, an I-type heterojunction is formed between the active layer and the guide layer, and the band of the valence band between the active layer and the guide layer is higher than that when the ZnS _0.07 Se _0.93 guide layer is used. The offset can be increased. When the band offset of the valence band between the active layer and the guide layer becomes large, holes can be efficiently confined in the active layer, resulting in a lower threshold current density and better long-life life than before. The semiconductor light emitting device is provided.

The problem of growth interruption during the formation of the laser structure or the problem of having to prepare a plurality of the same materials corresponding to the composition of each layer is Zn _{1 -x} C which constitutes the active layer.
(Zn _1-x Cd _x Se) _m (ZnS _y S containing d _x Se
e _1−y ) _n superlattice is used as a guide layer, or II−
The guide layer is formed of (ZnSe) _m (Cd
The problem is solved by using a Se) _n (ZnS) ₁ superlattice.

Thus, using only one cell of Cd alone or a compound containing it and only one cell of S alone or a compound containing it, a guide layer is formed without changing the molecular beam intensity of the cell. can do

[0024]

EXAMPLES The present invention will be described below with reference to examples.

Example 1 The semiconductor light emitting device of FIG. 1 is formed by the molecular beam epitaxial growth method using the molecular beam epitaxial apparatus shown in FIG. 4, for example.

First, this molecular beam epitaxial device will be described with reference to FIG. This apparatus has a growth chamber for epitaxial growth. The growth chamber is separated from or connected to the ion pump and other chambers (not shown) by opening and closing the gate valve 53. By pouring liquid nitrogen into the liquid nitrogen shroud 52 and exhausting it with an ion pump, the degree of vacuum in the growth chamber is 1 during the crystal growth.
It is maintained at 0 ^-10 Torr base.

In the growth chamber, ZnSe cell 40, Se cell 41, guide layer Cd cell 42, active layer Cd cell 43, guide layer ZnS cell 44, active layer are provided as cells for supplying the constituent elements of the growth layer. A ZnS cell 45 and a Mg cell 46 are provided. Further, cells 47 and 48 are provided as cells for supplying the dopant. The n-type dopant is supplied from the ZnCl ₂ cell 47. The cell 48 generates radical N ₂ used as a p-type dopant.

Shutters (not shown) are provided in front of the cells 40 to 48, respectively.
The on / off of the molecular beam supply from the cell is adjusted.

The temperature of each of the cells 40 to 47 is maintained at a set temperature by a temperature controller, and the intensity of the molecular beam from each cell is adjusted by changing the set temperature. Regarding the cell 48, the amount of N _{2 in} the radical state is adjusted by controlling the output of the RF power supply and the flow rate of N ₂ gas.

The substrate 49 for crystal growth is placed on the Mo block 51 in the growth chamber. The rotary heating device
The Mo block 51 is rotated while being heated. The temperature of the substrate 49 is 150 to 150 depending on the temperature controller in the rotary heating device.
It is kept at 400 ° C. A shutter 50 for adjusting a molecular beam reaching the surface of the substrate 49 is provided between the cells 40 to 48 and the substrate 49.

The degree of vacuum in the growth chamber is maintained at a degree of vacuum of the order of 10 ^-10 Torr by the liquid nitrogen shroud 52 and the ion pump. The beam flux of the molecular beam used should match the composition ratio of each layer, and the growth rate should be 500 nm /
The temperature of each cell is adjusted at different times.

An embodiment of a method of manufacturing the semiconductor light emitting device of FIG. 1 using the apparatus of FIG. 4 will be described below. In this embodiment, since the composition of the ZnCdSSe quaternary mixed crystal of the guide layer and the active layer is different, Cd and Zn should be adjusted according to the respective layers.
Two S cells are used. In this specification, "ZnCdSSe" _{is, Zn 1-x Cd x S} y Se
_1-y (0 <x ≦ 1, 0 ≦ y ≦ 1) will be simply expressed. Therefore, ZnCdSSe needs to contain Cd, but need not contain S. For example, Z
n _0.8 Cd _0.2 Se is included in ZnCdSSe.

First, after surface-treating the n-type GaAs (001) substrate 49, the substrate 49 is held by the Mo block and the substrate rotary heating device 51. After that, the shutter 50 in front of the n-type GaAs (001) substrate 49 set to the growth temperature is opened, and the Zn cell 40 and the Se cell 4 are
1. Using the ZnCl ₂ cell 47, the chlorine-doped n-type ZnSe layer 2 having a carrier density of 2 × 10 ¹⁸ cm ^-3 is 100 Å.
Grow crystals. Immediately thereafter, Zn cell 40, Mg cell 46, ZnS cell 44 for the cladding layer, Se cell 41,
Carrier density of chlorine doped with ZnCl2 cell 47 is 2 × 10 ¹⁸ cm ^- thickness of ³ 1.0 .mu.m n-type Zn _0.83
The Mg _0.17 S _0.2 Se _0.8 cladding layer 3 is formed.

Next, using the Zn cell 40, the Cd cell 42 for the guide layer, the ZnS cell 45 for the guide layer, and the Se cell 41, undoped Zn _0.9 Cd _0.1 S with a layer thickness of 700 Å is used.
_0.19 Se _{0.81 The} guide layer 4 is formed. The layer thickness of the guide layer is set to 700 Å because the light confinement coefficient is maximized at that layer thickness. Moreover, even if the guide layer is undoped, the layer thickness hardly contributes to the resistance of the device.

After that, the Zn cell 40, the Cd cell 43 for the active layer and the Se cell 41 are used to form an undoped Zn _0.8 Cd _0.2 Se active layer 5 having a layer thickness of 60 Å. in addition,
Using Zn cell 40, Cd cell 42, ZnS cell 45, and Se cell 41, undoped Zn _0.9 C with a layer thickness of 700Å
d _0.1 S _0.19 Se _{0.81 The} guide layer 6 is formed.

Thereafter, Zn cell 40, Mg cell 46, Z
A p-type Zn _0.83 Mg _0.17 S _0.2 Se _0.8 cladding layer 7 having a nitrogen-doped carrier density of 2 × 10 ¹⁷ cm ^{−3 and} a layer thickness of 1.0 μm was formed using the nS cell 44, Se cell 41, and active nitrogen cell 48. Form.

Thereafter, a Zn cell 40, a Se cell 41, and an active nitrogen cell 48 are used to obtain a nitrogen-doped carrier density of 8 ×.
The p-type ZnSe contact layer 8 of 10 ¹⁷ cm ^-3 is 100 Å
Crystal growth is performed to form a DH structure of 2 to 8. afterwards,
The shutter 51 is closed and the crystal growth is completed.

After taking out the substrate on which the above semiconductor laminated structure is formed, a mask having a stripe width of 3 μm is formed. After that, a 1000 Å thick SiO ₂ insulating film 11 is formed on the substrate in the region where the mask is not formed. A p-type electrode 9 is attached thereon, and an n-type electrode 10 is attached on the back surface of the GaAs substrate, and thus a light emitting device substrate having a cross section as shown in FIG. 1 is produced. After that, the substrate is cleaved to a cavity length of 0.5 mm, and a Fabry-Perot resonator is provided to complete the laser. Both cleaved end faces are uncoated and the reflectance is 25%. Internal loss is 7.
An 8 cm ^-1, cavity losses at 27.2cm ^-1,
The total loss is 35 cm ^-1 .

FIG. 7B shows the results of the band offsets of the conduction band and the valence band of each layer obtained by the above-mentioned common anion rule and common cation rule for the laser structure thus manufactured.

Comparing with the case of the conventional laser structure of FIG. 7A, it can be seen that the band offset of the valence band of the above laser structure is 132 meV, which is larger than that of the conventional laser structure.

FIGS. 8 (a) and 8 (b) respectively show Zn.
_1-x Cd _x S _y Se Changes in composition of Cd and S in _1-y and ratio ΔEv / ΔEg of band offset ΔEv of valence band to total band offset ΔEg are shown. Zn _1-x
The band gap of Cd _x S _y Se _1-y is fixed at 2.72 eV. From FIGS. 8A and 8B, ΔEv / ΔEg increases as the composition of Cd and S in the guide layer increases.
It can be seen that That is, Cd in the guide layer
By increasing the composition of S and S, the band offset of the valence band can be increased.

The characteristics of the light emitting device formed by the above method are as follows. Zn _0.83 Mg _0.17 S _0.2
The band gaps of the Se _0.8 clad layer, Zn _0.9 Cd _0.1 S _0.19 Se _0.81 guide layer, and Zn _0.8 Cd _0.2 Se active layer are 2.92 eV, 2.71 eV, and 2.46 eV, respectively. Regarding crystallinity, Zn _0.83 Mg _0.17 S _0.2 Se _{0
.8 Both the} cladding layer and Zn _0.9 Cd _0.1 S _0.19 Se _0.81 guide layer are lattice-matched to the GaAs substrate, and the half-width of the X-ray rocking curve of the epitaxial layer is 40 sec and the conventional ZnS _0.07 Se _0.93 guide layer emits light. It exhibits crystallinity similar to that of the device.

The optical and electrical characteristics of the above light emitting device are as follows. The oscillation wavelength is 504 nm. FIG. 9 shows the relationship between the injected current density and the mode gain in comparison between the above light emitting device and the conventional light emitting device. FIG.
The current density at which the mode gain is balanced with the total loss of 35 cm ⁻¹ is the threshold current density of the light emitting device and the conventional light emitting device. The threshold current density of the light emitting element is 440 A / c
m ^2, and is 13% reduced compared with the conventional light-emitting element. Due to these factors, the life of the semiconductor light emitting device can be extended.

As described above, by using the ZnCdSSe guide layer, a semiconductor light emitting device having excellent characteristics can be obtained. Conventionally, a ZnS _0.06 Se _0.94 layer has been used as a guide layer of a ZnSe-based compound semiconductor light emitting device. It has been generally considered that adding another element to such a ternary mixed crystal to form a quaternary mixed crystal makes it difficult to obtain a uniform crystal having a controlled composition. In addition, ternary mixed crystal ZnS
_{Even if a 0.06} Se _0.94 guide layer is used, it is difficult to form a guide layer having good crystallinity as it is reported that the continuous oscillation of the laser is finally succeeded at room temperature. Further, as described above, it has not been considered by those skilled in the art that it is preferable to increase the band offset of the valence band by using the ZnCdSSe guide layer instead of the ZnS _0.06 Se _0.94 guide layer. . Under such circumstances, the present inventor
Recognizing the effectiveness of using the SSe guide layer for the first time,
Then, a light emitting device shown in FIG. 1 was obtained by using a method for forming a mixed crystal having good crystallinity with a good limit.

Regarding the active layer or guide layer of the above laser structure, Zn _0.8 Cd _0.2 Se or Zn _0.9 Cd
_0.1 S _0.19 Se _0.81 instead of (ZnSe) _m (CdS)
Similar results can be obtained by using a superlattice such as _n (m and n are integers). (ZnSe) _m (CdS) _n (m and n are integers)
Is a superlattice in which m layers of ZnSe and n layers of CdS are laminated.

Example 2 The semiconductor light emitting device of the present invention shown in FIG. 2 is formed by using the molecular beam epitaxial device shown in FIG. The device of FIG. 5 differs from the device of FIG. 4 in that there is one Cd cell and one ZnS cell, and the number of cells is small. The temperature of the cell is adjusted so that the beam flux of the material used matches the composition ratio of each layer and the growth rate is 500 nm / hour.

Surface-treated n-type GaAs (00
1) Zn cell 54, Se on the substrate 61 (12 in FIG. 2)
Chlorine-doped n-type ZnSe layer 1 having a carrier density of 2 × 10 ¹⁸ cm ⁻³ using a cell 55 and a ZnCl ₂ cell 59.
3 was grown to 100 Å crystal, and immediately after that, Zn cell 54, M
g cell 58, ZnS cell 57, Se cell 55, ZnCl
Chlorine-doped carrier density of 2 × 1 using ₂ cells 59
N-type Zn _0.83 Mg _0.17 having a layer thickness of 0 ¹⁸ cm ^-3 of 1.0 μm
The S _0.2 Se _0.8 cladding layer 14 is formed.

Next, Zn _0.8 Cd _0.2 S having a layer thickness of 700Å
A guide layer 15 made of e / ZnS _0.2 Se _0.8 superlattice is formed. n-type Zn _0.83 Mg _0.17 S _0.2 Se _0.8 Zn cell 54, ZnS cell 57, Se cell 5 on the cladding layer 14.
5, the ZnS _0.2 Se _0.8 5 atomic layer 23 is crystal-grown.

Next, Zn cell 54, Cd cell 56, Zn
Using the S cell 57, the Zn _0.8 Cd _0.2 Se 2 atomic layer 24 is crystal-grown. ZnS _0.2 Se _0.8 5 atomic layer 23
Are crystal-grown, and the Zn _0.8 Cd _0.2 Se 2 atomic layer 24 is crystal-grown. Such a ZnS _0.2 Se _0.8 5 atomic layer 23,
The crystal growth of the Zn _0.8 Cd _0.2 Se2 atomic layer 24 by repeating 20 times _{((Zn 0.8 Cd 0.2 Se)} 2 (ZnS 0.2 Se
_0.8 ) ₅ ) ₂₀ Superlattice guide layer 15 is formed. After that, the Zn cell 54, the Cd cell 56, the Se cell 55 without interruption of growth.
Undoped Zn _0.8 Cd _0.2 Se with a layer thickness of 60 Å
The active layer 16 is formed. A Zn cell 54, a Cd cell 56, a ZnS cell 57, and a Se cell 55 are used thereon, and ((Zn _0.8 Cd _0.2 Se) ₂ (ZnS _0.2 Se) having a layer thickness of 700Å is used.
_0.8 ) ₅ ) ₂₀ Superlattice guide layer 17 is formed.

After that, the Zn cell 54, the Mg cell 58, and the Z cell are formed.
A p-type Zn _0.83 Mg _0.17 S _0.2 Se _0.8 clad layer 18 having a nitrogen-doped carrier density of 2 × 10 ¹⁷ cm ^{−3 and} a layer thickness of 1.0 μm is formed using an nS cell 57, a Se cell 55, and an active nitrogen cell 60. To do.

Thereafter, a Zn cell 54, a Se cell 55, and an active nitrogen cell 60 are used, and the nitrogen-doped carrier density is 8
The p-type ZnSe contact layer 19 of × 10 ¹⁷ cm ⁻³ is formed as 10
A 0 Å crystal is grown to form a DH structure.

After taking out the substrate on which the above semiconductor laminated structure was formed, the stripe width was 3 μm as in the first embodiment.
m mask is formed. And Si with a thickness of 1000Å
An O ₂ insulating film 22 is formed on the substrate in a maskless region. A p-type electrode 21 is attached thereon, and an n-type electrode 22 is attached on the back surface of the GaAs substrate to obtain a light emitting element substrate having a cross section as shown in FIG. After that, the substrate is cleaved to a cavity length of 0.5 mm, and a Fabry-Perot resonator is provided to complete the laser. Both cleaved end faces are uncoated and the reflectance is 25%. The internal loss was 7.8 cm ⁻¹ as in Example 1, and the cavity loss was 2
In 7.2cm ^-1, the total loss is 35 cm ^-1.

((Zn _0.8 Cd _0.2 Se) ₂ (ZnS _0.2 S
e _0.8 ) ₅ ) ₂₀ Superlattice is Zn _0.94 Cd _0.06 S _0.14 Se _0.86
Gives a band offset equivalent to (Z.Peng, et.al; Jpn.
J. Appl. Phys. 31 (1992) L1583). The band offsets of the conduction band and the valence band of each layer of the laser structure obtained by using the common anion rule and the common cation rule described above are shown in FIG.
It is shown in (c). As compared with the case of the conventional laser structure shown in FIG. 7A, it can be seen that the band offset of the valence band of the laser structure is 108 meV, which is larger than that of the conventional laser structure.

The characteristics of the light emitting device formed by the above method will be described below. Zn _0.83 Mg _0.17 S _0.2
Se _0.8 clad layer, ((Zn _0.8 Cd _0.2 Se) ₂ (Zn
S _0.2 Se _0.8 ) ₅ ) ₂₀ Superlattice guide layer, Zn _0.8 Cd _0.2
The band gap of the Se active layer is 2.92 eV,
They are 2.72 eV and 2.46 eV. Regarding crystallinity, Zn _0.83 Mg _0.17 S _0.2 Se _0.8 clad layer, ((Z
n _0.8 Cd _0.2 Se) ₂ (ZnS _0.2 Se _0.8 ) ₅ ) ₂₀ Both the superlattice guide layer is lattice-matched to the GaAs substrate, and the half-width of the X-ray rocking curve of the epitaxial layer is 45 s.
ec and the conventional ZnS _0.07 Se _0.93 guide layer show the same degree of crystallinity as the light emitting device.

The optical and electrical characteristics of the above light emitting device are as follows. The oscillation wavelength is 500 nm. FIG. 10 shows the relationship between the injected current density and the mode gain in comparison between the above light emitting device and the conventional light emitting device. As in Example 1, the mode gain of FIG. 10 has a total loss of 35 cm ^−1.
The current density that balances with is the threshold current density of the light emitting device and the conventional light emitting device. The threshold current density of the light emitting element is 460 A / cm ^2, which is 7% lower than that of the conventional light emitting element. Further, the resistivity of the element is 0.7Ω, which is about 30% lower than the conventional one. This is because there is no influence due to deterioration of the interface due to growth interruption. Due to these factors, the life of the semiconductor light emitting device can be extended.

(Embodiment 3) The semiconductor light emitting device of the present invention shown in FIG. 3 is formed by using the molecular beam epitaxial device shown in FIG. The device of FIG. 6 is different from the device of FIG. 5 in that the materials are ZnSe and CdS.
II-VI compounds such as e. The temperature of the cell is adjusted so that the beam flux of the material used matches the composition ratio of each layer and the growth rate is 500 nm / hour.

Surface-treated n-type GaAs (00
1) ZnSe cell 66, ZnCl2 cell 7 on the substrate 25
Carrier density of chlorine is 2 × 10 ¹⁸ cm
^-3 n-type ZnSe layer 26 is grown by 100Å crystal, and immediately thereafter, a ZnSe cell 66, a MgSe cell 69, a ZnS cell 68, a CdSe cell 67, and a ZnCl ₂ cell 70 are used to obtain a chlorine-doped carrier density of 2 × 10 ¹⁸ cm 2. layer thickness of ^-3 to form an n-type _{Zn 0. 83 Mg 0.17 S 0.2 Se} 0.8 cladding layer 27 of 1.0 .mu.m.

Next, ZnSe / CdS having a layer thickness of 700Å
A guide layer 28 made of an e / ZnS superlattice is formed. Specifically, the ZnSe 5 atomic layer 36 is crystal-grown on the n-type Zn _0.83 Mg _0.17 S _0.2 Se _0.8 cladding layer 27 using the ZnSe cell 66. Next, the CdSe 2 atomic layer 37 is crystal-grown using the CdSe cell 67. Z on it again
The ZnSe5 atomic layer 38 is crystal-grown using the nSe cell 66, and the ZnS4 atomic layer 39 is crystal-grown using the ZnS cell 68. Such ZnSe5 atomic layer 36, CdS
The crystal growth of the superlattice composed of the e2 atomic layer 37, the ZnSe5 atomic layer 38, and the ZnS4 atomic layer 39 is repeated 9 times to form the ((ZnSe) ₁₀ (CdSe) ₂ (ZnS) ₄ ) ₉ superlattice guide layer 28.

Thereafter, the ZnSe cell 66, without interruption of growth,
Undoped Z with a layer thickness of 60Å using CdSe cell 67
An n _0.8 Cd _0.2 Se active layer 29 is formed. Zn on it
Using the Se cell 66, the CdSe cell 67, and the ZnS cell 68, the ((ZnSe) ₁₀ (CdS) having a layer thickness of 700 Å is used.
e) ₂ (ZnS) ₄ ) ₉ superlattice guide layer 30 is formed.
After that, ZnSe cell 66, MgSe cell 69, ZnS
A cell 68 and an active nitrogen cell 71 are used to form a p-type Z having a nitrogen-doped carrier density of 2 × 10 ¹⁷ cm ^{−3 and} a layer thickness of 1.0 μm.
The n _0.83 Mg _0.17 S _0.2 Se _0.8 clad layer 31 is formed. Thereafter, a ZnSe cell 66 and an active nitrogen cell 71 are used to grow 100 Å crystal of a nitrogen-doped p-type ZnSe contact layer 32 having a carrier density of 8 × 10 17 cm -3.
6 to 32 DH structure is formed.

After taking out the substrate on which the semiconductor laminated structure is formed, a mask having a stripe width of 3 μm is formed as in the first embodiment. 1000 Å thick SiO ₂ insulating film 3
5 is formed on the substrate in the region where the mask is not formed by the laser. A p-type electrode 33 is attached thereon, and an n-type electrode 34 is attached on the back surface of the GaAs substrate to form a light emitting element substrate having a cross section as shown in FIG. After that, the substrate is cleaved to a cavity length of 0.5 mm, and a Fabry-Perot resonator is provided to complete the laser. Both cleaved end faces are uncoated and the reflectance is 25%. Internal loss is also 7.8 cm ^-1 Example 1, the cavity loss is 27.2Cm ^-1, the total loss is 35 cm ^-1.

((ZnSe) ₁₀ (CdSe) ₂ (Zn
S) _{4) 9} superlattice gives _{Zn 0.9 Cd 0.1 S 0 .2 Se} 0.8 equivalent band offset (Z.Peng, et.a
l; Jpn. J. Appl. Phys. 31 (199
2) L1583). FIG. 7D shows the results of the band offsets of the conduction band and valence band of each layer of the laser structure obtained by using the above-mentioned common anion rule and common cation rule. Compared with the case of the conventional laser structure of FIG. 7A, the band offset of the valence band of the laser structure is 1
It can be seen that it is 35 meV, which is larger than that of the conventional laser structure.

The characteristics of the light emitting device formed by the above method will be described. Zn _0.83 Mg _0.17 S _0.2 Se _0.8 clad layer, ((ZnSe) ₁₀ (CdSe) ₂ (Zn
The band gaps of the S) ₄ ) ₉ superlattice guide layer and the Zn _0.8 Cd _0.2 Se active layer are 2.92 eV and 2.72 e, respectively.
V is 2.46 eV. Regarding crystallinity, Zn _0.83
Mg _{0. 17} S _0.2 Se _0.8 cladding layer, ((ZnSe)
₁₀ (CdSe) ₂ (ZnS) ₄ ) ₉ Superlattice guide layer is lattice-matched to the GaAs substrate, and X of the epitaxial layer is formed.
The full width at half maximum of the rocking curve of the line is 40 sec and the conventional Z
The crystallinity is similar to that of the light emitting device using the nS _0.07 Se _0.93 guide layer. The optical and electrical characteristics of the laser are as follows. The oscillation wavelength is 504 nm.

FIG. 11 shows the relationship between the injected current density and the mode gain in comparison between the above light emitting device and the conventional light emitting device. As in the first embodiment, the mode gain of FIG.
The current density balanced with 5 cm ⁻¹ is the threshold current density of the light emitting device and the conventional light emitting device. The threshold current density of the light emitting element is 440 A / cm ^2, which is 13% lower than that of the conventional light emitting element. Due to these factors, the life of the semiconductor light emitting device can be extended.

In the above embodiment, an example using the Zn _0.8 Cd _0.2 Se active layer has been described, but the active layer is (Z
n _1-x Cd _x S _y Se _1-y ) _m (Zn _1-z Cd _{z St} Se _1-t ) _n
Superlattice (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1, 0 ≦ t
≦ 1, a <(xm + yn) / (m + n), (zm + t
n) / (m + n) <b, m and n are integers).

[0065]

According to the present invention, by adopting the ZnCdSSe guide layer, a semiconductor light emitting device having a threshold current density smaller than that of the conventional one, a long life, and high reliability is provided. In addition, only one cell of Cd alone or a compound containing it or only one cell of S alone or a compound containing it is used without changing the molecular beam intensity, and Zn _1-x Cd _x forming the active layer is used. Including Se (Zn _1-x Cd _x S
e) _m (ZnS _y Se _{1 -y} ) _n superlattice may be used to form the guide layer, or a II-VI group compound may be used to form the guide layer (Z
By using the nSe) _m (CdSe) _n (ZnS) ₁ superlattice, it is possible to eliminate the interruption of epitaxial growth. As a result, a semiconductor issuing device having low resistivity and good crystallinity is manufactured.

[Brief description of drawings]

FIG. 1 is a sectional view of a semiconductor light emitting device according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a semiconductor light emitting device according to a second embodiment of the present invention.

FIG. 3 is a sectional view of a semiconductor light emitting device according to a third embodiment of the present invention.

FIG. 4 is a sectional view of a molecular beam epitaxial device for forming the semiconductor light emitting device of the first embodiment of the present invention.

FIG. 5 is a cross-sectional view of a molecular beam epitaxial device for forming the semiconductor light emitting device of the second embodiment of the present invention and practicing the crystal growth method of the present invention.

FIG. 6 is a cross-sectional view of a molecular beam epitaxial device for forming the semiconductor light emitting device of the third embodiment of the present invention and practicing the crystal growth method of the present invention.

FIG. 7 is a diagram showing band offsets of conduction band and valence band between respective layers of the semiconductor light emitting device of the present invention and the conventional semiconductor light emitting device.

FIG. 8 is a diagram showing a ratio of a band offset of a valence band to a total of a ZnCdSSe guide layer due to a change in a composition of Cd and S.

FIG. 9 is a graph showing the relationship between the threshold current density and the mode gain of the light emitting device of the first embodiment and the conventional light emitting device of the present invention.

FIG. 10 is a graph showing the relationship between the threshold current density and the mode gain of the light emitting device of the second embodiment and the conventional light emitting device of the present invention.

FIG. 11 is a graph showing the relationship between the threshold current density and the mode gain of the light emitting device of the third embodiment of the present invention and the conventional light emitting device.

FIG. 12 is a sectional view of a conventional semiconductor light emitting device.

[Explanation of symbols]

4 Zn _0.9 Cd _0.1 S _0.19 Se _0.81 guide layer 5 Zn _0.8 Cd _0.2 Se active layer 6 Zn _0.9 Cd _0.1 S _0.19 Se _0.81 guide layer 15 ((Zn _0.8 Cd _0.2 Se) ₂ (ZnS _0.2 S
e _0.8 ) ₅ ) ₂₀ Superlattice guide layer 17 ((Zn _0.8 Cd _0.2 Se) ₂ (ZnS _0.2 S
e _{0.8) 5) 20} superlattice guide layer 23 Zn _0.8 Cd _0.2 Se2 atomic layer 24 ZnS _0.2 Se _0.8 5 atomic layers _{28 ((ZnSe) 10 (CdSe} ) 2 (ZnS) 4) 9
Superlattice guide layer 30 ((ZnSe) ₁₀ (CdSe) ₂ (ZnS) ₄ ) ₉
Superlattice guide layer 36 ZnSe5 atomic layer 37 CdSe2 atomic layer 38 ZnSe5 atomic layer 39 ZnS4 atomic layer 42 Cd cell (for guide layer) 43 Cd cell (for active layer) 44 ZnS cell (for guide layer) 45 ZnS cell (active layer) 56 Cd cell 57 ZnS cell 66 ZnSe cell 67 CdSe cell 68 ZnS cell 69 MgSe cell

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Minor Kubo 1006 Kadoma, Kadoma City, Osaka Prefecture, Matsushita Electric Industrial Co., Ltd.

Claims (11)

[Claims] 1. A semiconductor light emitting device comprising a GaAs substrate and a II-VI group compound semiconductor laminated structure formed on the GaAs substrate, wherein the semiconductor laminated structure comprises a ZnCdSSe active layer and the active layer. And a pair of ZnCdSSe guide layers sandwiching between the guide layers, the composition of Cd in the active layer is larger than the composition of Cd in the guide layer, and the composition of S in the active layer is S in the guide layer.
A semiconductor light emitting device having a composition smaller than that of 2. The laminated structure includes a pair of II-VI group compound semiconductor clad layers sandwiching the active layer and the guide layer, wherein the active layer, the guide layer and the clad layer are separated light confinement hetero layers. The semiconductor light emitting device according to claim 1, wherein the semiconductor light emitting device forms a structure. 3. At least one of the pair of guide layers is formed of a (Zn _1-x Cd _x Se) _m (ZnS _y Se _{1 -y} ) _n superlattice, and the active layer constitutes the superlattice. Zn _1-x Cd _x Se or Zn _1-x Cd _x Se and Zn _1-u Cd _u S _v Se _1-v (0 <
The semiconductor light emitting device according to claim 1, wherein the semiconductor light emitting device is formed of a multi-layer of u <1, 0 <v <1, x <u, y <v). 4. At least one of the pair of guide layers, each layer being composed of a binary crystal (ZnSe) _m (CdS).
The semiconductor light emitting device according to claim 1, wherein the semiconductor light emitting device is formed of e) _n (ZnS) _l (m, n, and l are integers). 5. At least one of the pair of guide layers comprises (Zn _1-a Cd _a S _b Se _1-b ) _m (Zn _1-c Cd _c S _d S
e _1−d ) _n superlattice (0 ≦ c ≦ 1, 0 ≦ d ≦ 1, (am + b
n) / (m + n) <x, y <(cm + dn) / (m +
The semiconductor light emitting device according to claim 1, wherein n), m, and n are integers. 6. The active layer comprises (Zn _1-x Cd _x S _y Se
_1-y ) _m (Zn _1-z Cd _{z St} Se _1-t ) _n superlattice (0 ≦ x ≦
1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1, 0 ≦ t ≦ 1, a <(xm
+ Yn) / (m + n), (zm + tn) / (m + n) <
The semiconductor light emitting device according to claim 1, wherein b, m, and n are integers. 7. The active layer comprises (Zn _1-a Cd _a S _b Se
_1-b) is formed from _m (Zn _{1 over c} Cd c S _d Se _{1 over} d) _n superlattice, at least one of the pair of guiding layer, (Zn _1-x C
d _x S _y Se _1-y ) _k (Zn _1-z Cd _{z St} Se _1-t ) _l (m,
n, k, and l are integers, 0 ≦ z ≦ 1, 0 ≦ t ≦ 1, (xk +
yl) / (k + l) <(am + bn) / (m + n),
(Cm + dn) / (m + n) <(zk + tl) / (k +
The semiconductor light emitting device according to claim 1, which is formed from l)). 8. A GaAs substrate, and a II-VI group compound semiconductor laminated structure formed on the GaAs substrate,
The semiconductor laminated structure includes a ZnCdSSe active layer and a pair of ZnCdSSe guide layers sandwiching the active layer,
The composition of Cd in the active layer is larger than that of Cd in the guide layer, and the composition of S in the active layer is S in the guide layer.
A method for manufacturing a semiconductor light emitting device having a composition smaller than that of Cd, wherein a single cell of Cd alone or a compound containing the same is used as a source of Cd, and molecular beam epitaxial growth for forming the guide layer or the active layer is performed. A method for manufacturing a semiconductor light emitting device, comprising: 9. The method of manufacturing a semiconductor light emitting device according to claim 8, wherein in the molecular beam epitaxial growth step, the guide layer and the active layer are formed without changing the molecular beam intensity of the only cell. 10. A GaAs substrate and a II-VI group compound semiconductor laminated structure formed on the GaAs substrate, the semiconductor laminated structure comprising a ZnCdSSe active layer and a pair of ZnCdSSe guide layers sandwiching the active layer. And a composition of Cd in the active layer is larger than a composition of Cd in the guide layer and a composition of S in the active layer is smaller than a composition of S in the guide layer. A method of manufacturing a semiconductor light-emitting device, which comprises a molecular beam epitaxial growth step of forming the guide layer or the active layer using only a single cell of S alone or a compound containing the same as a source of S. . 11. In the molecular beam epitaxial growth step, without changing the molecular beam intensity of the only one cell,
The method of manufacturing a semiconductor light emitting device according to claim 9, wherein the guide layer and the active layer are formed.