JPH06268331A - Semiconductor light emitting device - Google Patents

Abstract

PURPOSE:To provide a semiconductor light emitting device employing a II-IV compound semiconductor in which operating voltage or operating current can be decreased. CONSTITUTION:The semiconductor light emitting device comprises a p-type InP substrate 1, a p-type clad layer 2 of Cd1-u-vZnuMgvSe (0<=u, v<=1) formed thereon, an active layer 3 of Cd1-w-xZnwMgxSe (0<=w, x<=1) formed thereon, and an n-type clad layer 4 of Cd1-y-zZnyMgzSe (0<=y, z<=1).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser device using a II-VI group compound semiconductor, a semiconductor light emitting device such as a light emitting diode device.

[0002]

2. Description of the Related Art Conventionally, various compound semiconductors have been used for semiconductor lasers, but recently, II-VI such as ZnSe has been used.
Group compound semiconductors are drawing attention. This is a wide bandgap (wide gap) equal to or greater than the energy equivalent to the wavelength of light in the visible wavelength region of II-VI group compound semiconductors.
It is possible to use as a visible light emitting device material.

In particular, the operating wavelength range of semiconductor lasers and light-emitting diodes made of III-V group compound semiconductor materials such as GaAlAs and InGaAlP is longer than that of green, whereas the wavelength range of wide-gap II-VI group compound semiconductors is longer. May be operating up to short blue or ultraviolet light. Therefore, the advantages of the conventional semiconductor light emitting device such as small size, light weight, low operating voltage, and high reliability can be applied to the short wavelength region, and the density of the optical disc can be increased. Furthermore, full-color outdoor message boards can be realized. FIG. 6 is a sectional view showing a main structure of a blue-green light emitting semiconductor laser device using a conventional wide gap II-VI group compound semiconductor.

In the figure, reference numeral 61 indicates an n-type GaAs substrate, and on this n-type GaAs substrate 61, an n-type ZnSe layer 63,
n-type ZnSSe layer 64, n-type ZnSe layer 65, CdZn
Se quantum well layer 66, p-type ZnSe layer 67, p-type ZnS
The Se layer 68 and the p-type ZnSe layer 69 are sequentially stacked. A p-side Au electrode 71 is provided on the p-type ZnSe layer 69 via a polyimide layer 70 having an opening, while an n-side In electrode 72 is provided on the n-type GaAs substrate 61.

It has been reported that the current injection type semiconductor laser device configured as described above can perform continuous oscillation at liquid nitrogen temperature or pulse oscillation at room temperature (A
pplied Physics Letters, Vol.59, pp.1272-1274 (199
1)). FIG. 7 is a cross-sectional view showing a main structure of a light emitting diode device using a conventional wide gap II-VI group compound semiconductor.

In the figure, reference numeral 81 denotes a p-type GaAs substrate, and the p-type ZnSe layer 8 is provided on the p-type GaAs substrate 81.
2, n-type ZnSe layer 83 is sequentially formed.
An In electrode 84 is provided on the Se layer 83, and a p-type G
An AuZn electrode 85 is provided on the aAs substrate 81.

According to such a light emitting diode device,
It has been reported that it is possible to emit light at room temperature (Exte
nded Abstracts of the 1992 International Conferenc
e onSolid State Devices and Materials, Tsukuba, p
p.342-344 (1992)).

However, continuous oscillation at room temperature and high-efficiency light emission of a light emitting diode device, which are necessary for a practical semiconductor laser device, have not been realized so far. This is because the operating voltage of a semiconductor light emitting device using a wide gap II-VI group compound semiconductor such as ZnSe is
It is significantly higher than that of a group compound semiconductor material, and as is particularly remarkable in semiconductor laser devices, electrons and holes (carriers) injected at high temperatures above room temperature are not well confined in the light emitting layer, and the operation The high current was the main cause.

As described below, the reason why the operating voltage is remarkably increased is not a problem in the conventional semiconductor light emitting device using the III-V group compound semiconductor material.
This is due to the problems peculiar to the semiconductor light emitting device using a wide-gap II-VI group compound semiconductor such as e.

That is, when current is injected into a wide-gap II-VI group compound semiconductor having a p-type conductivity type such as ZnSe through a metal electrode or a heterojunction with another semiconductor material, a large voltage drop occurs. By being forced. This is an essential problem in wide-gap II-VI group compound semiconductors such as ZnSe, in which the Schottky barrier with a metal and the hetero barrier with another semiconductor become large.

For example, in the case of the semiconductor laser device shown in FIG. 6, as shown in FIG.
The Schottky barrier with the nSe layer 69 becomes large, and it is necessary to apply a large voltage in order to prevent the holes h from being reflected by the p-type ZnSe layer 69.

Further, in the case of the light emitting diode device shown in FIG. 7, as shown in FIG. 8B, the hetero barrier formed by the p-type GaAs substrate 81 and the p-type ZnSe layer 82 becomes large, so that the p-type ZnSe is formed. To prevent the holes h from being reflected by the layer 82, it is necessary to apply a large voltage.

FIG. 9 is a sectional view showing the structure of the main part of a semiconductor laser device capable of suppressing an increase in operating current, which has been a problem in the semiconductor light emitting devices of FIGS. 6 and 7 (Electronics Lett).
ersVol.28, pp.1798-1799 (1992)).

In the figure, reference numeral 91 denotes an n-type GaAs substrate, and n-type ZnMgSe is placed on the n-type GaAs substrate 91.
S cladding layer 92, ZnSe / ZnMgSSeMQW active layer 93, p-type ZnMgSSe cladding layer 94, p-type Z
The nSe layer 95 is sequentially formed. This p-type ZnSe
The layer 95 is made of Au through a polyimide layer 96 having an opening.
The / Pd electrode 97 is in contact, and the n-type GaAs substrate 91 is in contact with the In electrode 98.

According to the semiconductor laser device having such a structure, although the confinement of the injected carriers at a high temperature is improved, the cause of the high operating voltage is not removed at all, but rather the p-type ZnMgSSe cladding is used. Since the acceptor level in the layer 94 becomes deeper, there is a problem that the resistivity and the operating voltage increase.

As a result of using ZnMgSeS,
For the lattice matching between the GaAs substrate 91 and each ZnMgSeS layer, it is necessary to accurately control the composition ratio of Zn and Mg and the composition ratio of Se and S.

However, since it is difficult to control such an accurate composition ratio, it is not possible to produce a good quality crystal with good reproducibility, and a semiconductor laser device using ZnMgSeS as a wide gap II-VI group compound semiconductor. Then
No oscillation was obtained at room temperature.

[0018]

As described above, in the conventional semiconductor light emitting device using the wide gap II-VI group compound semiconductor, compared with the semiconductor light emitting device using the III-V group compound semiconductor, Since the operating voltage and operating current are large, there is a problem that continuous oscillation at room temperature and highly efficient light emission are difficult.

The present invention has been made in consideration of the above circumstances. An object of the present invention is, firstly, to provide a semiconductor light emitting device using a wide gap II-VI group compound semiconductor having a low operating voltage. Especially. Secondly, it is to provide a semiconductor light emitting device using a wide gap II-VI group compound semiconductor having a low operating voltage and a small operating current.

[0020]

In order to achieve the above first object, a semiconductor light emitting device (claim 1) of the present invention comprises:
A semiconductor substrate made of nP, and Cd _1-xy Zn _x Mg _y Se (0 ≦ x ≦ 1, 0 ≦ y ≦ 1) formed on this semiconductor substrate
And a light emitting semiconductor layer made of

Further, in order to achieve the above second object,
A semiconductor light emitting device (claim 2) of the present invention comprises a semiconductor substrate made of InP, and Cd formed on the semiconductor substrate.
_1-uv Zn _u Mg _v Se (0 ≦ u ≦ 1, 0 ≦ v ≦ 1), a first conductivity type cladding layer, and Cd _{1 -wx} Zn _w Mg formed on the first conductivity type cladding layer. _x Se (0 ≦ w ≦ 1, 0
≦ x ≦ 1) and a Cd _{1 -yz} Zn _y Mg _z Se (0 ≦ y ≦ 1, 0 formed on the light emitting semiconductor layer.
And a second conductivity type cladding layer of ≦ z ≦ 1). The light emitting semiconductor layer, the first conductivity type cladding layer and the second conductivity type cladding layer are preferably formed by a molecular beam epitaxy method.

[0022]

According to the study by the present inventors, the valence band of InP and Cd _1-xy Zn _x which is one of II-VI group compound semiconductors.
The difference of the valence band from Mg _y Se (0 ≦ x ≦ 1, 0 ≦ y ≦ 1) is
II-VI such as ZnMgSSe used for the active layer and the valence band of GaAs that has been used as a substrate.
Group compound semiconductors (excluding Cd _1-xy Zn _x Mg _y Se)
It was found to be sufficiently smaller than the difference from the valence band of.

Therefore, according to the present invention (claims 1 and 2), a semiconductor light emitting device having a low operating voltage can be obtained. Further, since InP and Cd _1-xy Zn _x Mg _y Se are lattice-matched, there are few manufacturing problems.

According to the research conducted by the present inventors, Cd
It was found that the controllable bandgap range of _1-xy Zn _x Mg _y Se is wider than that of other II-VI group compound semiconductors.

Therefore, by using Cd _1-xy Zn _x Mg _y Se as the material of the active layer and the cladding layer, the band gap relationship required for the active layer and the cladding layer, that is, the band gap of the cladding layer becomes active. It is possible to increase the bandgap difference between the clad layer and the active layer to the extent that carriers do not leak from the active layer to the clad layer even at high temperatures above room temperature, satisfying the condition that the layer is larger than that of the layer, and to increase the operating current. Can be made smaller.
Therefore, according to the present invention (claim 2), a semiconductor light emitting device having a low operating voltage and a small operating current can be obtained.

[0026]

Embodiments will be described below with reference to the drawings. FIG. 1 is a sectional view showing a main structure of a double hetero structure semiconductor laser device according to a first embodiment of the present invention.

In the figure, 1 indicates a p-type InP substrate,
On this p-type InP substrate 1, p-type Cd _1-xy Zn _x Mg _y Se (0 ≦ 1 having a thickness of 1 μm and a carrier concentration of 10 ¹⁸ cm ⁻¹⁾ is formed.
x ≦ 1, 0 ≦ y ≦ 1) The cladding layer 2 is formed. Hereinafter, Cd _1-xy Zn _x Mg _y Se (0 ≦ x ≦ 1, 0 ≦ y ≦ 1)
Is simply expressed as CdZnMgSe.

On the p-type CdZnMgSe cladding layer 2, an undoped CdZnMgSe active layer 3 having a thickness of 50 nm, an n-type C having a thickness of 1 μm and a carrier concentration of 10 ¹⁸ cm ^−1.
The dZnMgSe clad layer 4 is sequentially formed.

On the n-type CdZnMgSe cladding layer 4, SiO having a stripe-shaped opening with a width of 7 μm is formed.
_{A 2} insulating film 5 is formed, an n-side electrode 6 that contacts the n-type CdZnMgSe cladding layer 4 through the opening is provided on the SiO ₂ insulating film 5, and a p-type I
A p-type electrode 7 is provided on the nP substrate 1.

Here, the undoped CdZnMgSe active layer 3, the p-type CdZnMgSe cladding layer 2 and the n-type C.
The composition ratio of Cd, Zn and Mg of the dZnMgSe clad layer 4 is such that the undoped CdZnMgSe active layer 3, the p-type CdZnMgSe clad layer 2 and the n-type CdZnMg.
The lattice constant of the Se clad layer 4 is substantially equal to that of the p-type InP substrate 1, and the band gap of the undoped CdZnMgSe active layer 3 is smaller than that of the p-type CdZnMgSe clad layer 2 and the n-type CdZnMgSe clad layer 4. Have been chosen as. Such Cd
The active layer made of ZnMgSe layer, the cladding layer, etc. are preferably formed by molecular beam epitaxy.

In the double heterostructure semiconductor laser device having the structure shown in this embodiment, the band gap of the active layer 3 is 2.65 eV, and the band gaps of the p-type CdZnMgSe cladding layer 2 and the n-type CdZnMgSe cladding layer 4 are 3. Resonator length 500 for the case of 00eV
It was cleaved to μm, mounted on a copper heat sink using In solder, and its characteristics were evaluated at room temperature.

As a result, the oscillation wavelength is 470 nm,
The oscillation threshold current in continuous operation was 80 mA. The operating voltage at this time was 3.5V. The maximum oscillation temperature of continuous operation was 60 ° C.

As described above, by adopting the device structure shown in this embodiment, not only continuous oscillation at room temperature, which has been difficult in the past, but also at a high temperature necessary to ensure sufficient reliability for practical use at room temperature are realized. It was found that the oscillation of

The reason why the operating voltage can be lowered in this way is that p
As the p-type substrate and p-type clad layer, p-type InP,
As a result of using p-type CdZnMgSe, the hetero barrier is lowered, and as shown in FIG. 2, the difference between the valence band of the p-type InP substrate 1 and the valence band of the p-type CdZnMgSe clad layer 2 is reduced, and the p-type From InP substrate 1 to p-type CdZnMg
This is because it becomes easy to inject holes into the Se clad layer 2.

When the operating voltage is lowered in this way, the amount of heat generated is correspondingly reduced, and the temperature characteristics are improved. Further, all the CdZnMgSe layers 1 to 4 are lattice-matched with the p-type InP substrate 1, and the group VI element is Se1.
Since it is a kind of the above, it was also a factor of improving the temperature characteristics that a good crystal without defects such as dislocation could be produced.

Further, since the controllable bandgap range of CdZnMgSe is wider than that of other II-VI group compound semiconductors, undoped CdZ can be used even at a temperature higher than room temperature.
The undoped CdZnMgSe active layer 3 to the extent that carriers do not leak from the nMgSe active layer 3 to the p-type CdZnMgSeSe cladding layer 2 and the n-type CdZnMgSeSe cladding layer 4.
And p-type CdZnMgSe clad layer 2, n-type CdZnM
The band gap difference between each of them and the gSe clad layer 4 can be increased. Therefore, the confinement of injected carriers is improved and the operating current is reduced.

In the double heterostructure semiconductor laser device of this embodiment, the bandgap energy of the undoped CdZnMgSe active layer 3 is Cd, Zn and M.
The oscillation wavelength at room temperature could be changed from 630 nm to 400 nm by changing the composition of g.

In this case, the undoped CdZnMgSe active layer 3, the p-type CdZnMgSe cladding layer 2 and the n-type C are used.
By setting the band gap difference between each of them and the dZnMgSe cladding layer 4 to be constant at 0.35 eV, the maximum oscillation temperature in continuous operation was about 60 ° C., which was almost constant regardless of the oscillation wavelength.

Further, the undoped CdZnMgSe active layer 3, the p-type CdZnMgSe clad layer 2, and the n-type CdZn.
By increasing the band gap difference between each of them and the MgSe clad layer 4, a double hetero structure semiconductor laser device having a high maximum oscillation temperature was obtained. In the range of 100 ° C. or lower, an increase in the maximum oscillation temperature of about 10 ° C. was observed with an increase in the band gap difference of 0.01 eV. here,
When CdZnSe lattice-matched to InP is used for the active layer, the p-type CdZnMgSe cladding layer 2 and the n-type CdZn are used.
By using the band gap of the MgSe clad layer 4 as it is at 3.0 eV, continuous operation at 200 ° C. or higher could be easily realized. FIG. 3 is a sectional view showing the main structure of a double hetero structure semiconductor laser device according to the second embodiment of the present invention.

In the figure, reference numeral 11 denotes a p-type InP substrate. On the p-type InP substrate 11, a thickness of 200 nm,
P-type CdZnMgSe with a carrier concentration of 2 × 10 ¹⁸ cm ⁻¹
Buffer layer 12, thickness 1 μm, carrier concentration 1 × 10 ¹⁸
cm ⁻¹ p-type CdZnMgSe cladding layer 13, thickness 5
0 nm undoped CdZnMgSe active layer 14, thickness 1 μm, carrier concentration 1 × 10 ¹⁸ cm ⁻¹ n-type CdZn
An MgSe clad layer 15 and an n-type CdZnMgSe contact layer 16 having a thickness of 0.5 μm and a carrier concentration of 5 × 10 ¹⁸ cm ⁻¹ are sequentially formed. In addition, n-type CdZnMg
A SiO ₂ insulating film 17 having a stripe-shaped opening having a width of 7 μm and an n-side electrode 18 are sequentially formed on the Se contact layer 16, and the n-type CdZnMgSe contact layer 16 is formed on the n-side electrode 18 through the opening. I have a contact. The p-type InP substrate 11 is provided with the p-type electrode 19.

Here, the undoped CdZnMgSe active layer 14, the p-type CdZnMgSe clad layer 13 and n.
The lattice constant of the CdZnMgSe cladding layer 15 is p-type I.
Undoped CdZnM almost equal to nP substrate 11
The band gap of the gSe active layer 14 is p-type CdZnMg.
The p-type CdZnMgSe clad layer 13 and the undoped CdZn are formed so as to be smaller than the band gaps of the Se clad layer 13 and the n-type CdZnMgSe clad layer 15.
The compositions of Cd, Zn and Mg of the MgSe active layer 14 and the n-type CdZnMgSe cladding layer 15 are set.

Further, the p-type CdZnMgSe buffer layer 1
2 has a lattice constant substantially equal to that of the p-type InP substrate 11, and its band gap is p-type CdZnMgSe clad layer 1.
P-type CdZ so as to be smaller than the band gap of 3
The composition of Cd, Zn and Mg of the nMgSe buffer layer 12 is set.

The lattice constant of the n-type CdZnMgSe contact layer 16 is substantially equal to that of the p-type InP substrate 11, and the band gap thereof is the n-type CdZnMgSe clad layer 15.
N-type CdZn to be smaller than the band gap of
The composition of Cd, Zn and Mg of the MgSe contact layer 16 is set. It is desirable that the active layer, the clad layer, and the like made of such a CdZnMgSe layer be formed by a molecular beam epitaxy method.

In the double hetero structure semiconductor laser device having the structure shown in this embodiment, undoped CdZnMgS
e active layer 14 has a bandgap of 2.65 eV and p-type C
dZnMgSe cladding layer 12 and n-type CdZnMg
The band gap of the Se clad layer 15 is set to 3.00.
eV, p-type CdZnMgSe buffer layer 12 having a bandgap of 2.00 eV and n-type CdZnMgMgSe contact layer 16 having a bandgap of 2.00 eV were cleaved to a resonator length of 500 μm, and In solder was used for a copper heat sink. Mounted at room temperature, and its characteristics were evaluated at room temperature.

As a result, the oscillation wavelength is 470 nm,
The oscillation threshold current in continuous operation was 75 mA. The operating voltage at this time was 3.0V. The maximum oscillation temperature of continuous operation was 90 ° C. That is, a double heterostructure semiconductor laser device having better operating characteristics than the double heterostructure semiconductor laser device of the previous embodiment was obtained.

One of the reasons for obtaining such good operation characteristics is the p-type InP substrate 11 and the p-type CdZnMgSe.
Between the cladding layer 13 and the p-type CdZnMgSe cladding layer 13, a p-type CdZ having a smaller bandgap is formed.
This is because the nMgSe buffer layer 12 is inserted.

That is, by adding the p-type CdZnMgSe buffer layer 12, as shown in FIG.
Since the hetero barrier between the P substrate 11 and the p-type CdZnMgSe cladding layer 13 becomes smaller, holes h can be injected from the InP substrate 11 into the p-type CdZnMgSe cladding layer 13 with a smaller voltage drop. Because it became.

The other factor is that the n-type CdZnMgSe clad layer 1 is formed on the n-type CdZnMgSe clad layer 15.
N-type CdZnMgSe having a band gap smaller than 5
By forming the contact layer 16, undoped CdZ
This is because high-concentration doping can be performed without adversely affecting the nMgSe active layer 14, the influence of surface oxidation is reduced, and the voltage drop at the electrode contact can be suppressed.

By reducing the voltage drop at these substrate interfaces and electrodes, the operating voltage was reduced, and the suppression of excessive heat generation led to the improvement of the temperature characteristics. In addition, the reduction of the operating voltage by these has an effect independently of each other, and even if either of the measures is taken, the effect of reducing the operating voltage is about half.

The effect of reducing the voltage drop by the p-type CdZnMgSe buffer layer 12 at the substrate interface is the p-type CdZnMg
It appeared by using CdZnMgSe having a composition with a bandgap smaller than that of the Se clad layer 13. This effect is
The following buffer layer structure showed a better effect.

That is, the composition of at least the side of the p-type CdZnMgSe buffer layer 12 in contact with the p-type InP substrate 11 has a bandgap of 2.3 eV or less.
When using MgSe, the voltage drop could be kept particularly low. More preferably, CdZn containing no Mg
When Se was brought into contact with the p-type InP substrate 11, the voltage drop could be suppressed to a particularly low level.

The p-type CdZnMgSe buffer layer 1
2 is composed of a plurality of layers or a layer whose composition gradually changes, and the band gap on the p-type InP substrate 11 side is small,
By setting the band gap on the p-type CdZnMgSe cladding layer 13 side to be large, the voltage drop could be suppressed to a particularly small value. This is because reducing the hetero barrier between the p-type InP substrate 11 and the p-type CdZnMgSe buffer layer 12 is particularly effective in reducing the voltage drop.

The voltage drop reducing effect in the electrode contact is obtained when CdZnMgSe of the n-type CdZnMgSe contact layer 16 is selected so that the bandgap of the n-type CdZnMgSe contact layer 16 is smaller than that of the n-type CdZnMgSeSe cladding layer 15. Appeared. This effect was more excellent in the following contact layer structure.

That is, the composition of at least the side in contact with the n-side electrode 18 in the n-type CdZnMgSe contact layer 16 has a bandgap of 2.3 eV or less.
When using Se, the voltage drop could be kept particularly low. More preferably, CdZnSe containing no Mg
The voltage drop can be suppressed to a particularly low level when the electrode contacts the n-side electrode 18.

The n-type CdZnMgSe contact layer 16 is composed of a plurality of layers or layers whose composition changes gradually, and the band gap on the n-side electrode 18 side is small and the band gap on the n-type CdZnMgSe clad layer 15 side is large. By setting to, the voltage drop could be suppressed to a particularly small value.

This is the n-side electrode 18 and the n-type CdZnMgS
It is particularly effective in reducing the voltage drop that the barrier between the e-contact layer 16 and the e-contact layer 16 is made small, that the composition having a small band gap is easily doped at a high concentration, and that the composition of Mg that is easily oxidized is reduced near the surface. Because there is.
Similar effects were also observed when the surface layer of CdZnMgSe was configured as described above in the step of forming a semiconductor layer on CdZnMgSe.

In the double hetero structure semiconductor laser device having the structure shown in this embodiment, undoped CdZn is used.
The band gap energy of the MgSe active layer 14 is C
The oscillation wavelength at room temperature could be changed from 630 nm to 400 nm by changing the composition of d, Zn and Mg.

In this case, the band gap difference between the undoped CdZnMgSe active layer 14 and the p-type CdZnMgSe cladding layer 13 and the n-type CdZnMgSeSe cladding layer 15 is fixed at 0.35 eV.
The maximum oscillation temperature in continuous operation was about 90 ° C., which was almost constant regardless of the oscillation wavelength.

Further, the undoped CdZnMgSe active layer 14, the p-type CdZnMgSe clad layer 13, and the n-type Cd.
When the band gap difference between the ZnMgSe clad layer 15 and the ZnMgSe clad layer 15 was increased, a high maximum oscillation temperature was obtained. Specifically, in the range of 100 ° C. or lower, the increase in the band gap difference is 10 ° C. per 0.01 eV.
A rise in the maximum oscillation temperature was observed. Further, when CdZnSe lattice-matched to InP was used for the active layer, continuous operation at 230 ° C. or higher could be easily realized by using the band gap of the cladding layer as it was at 3.0 eV.

In the double hetero structure semiconductor laser device of this embodiment, the current confinement structure due to the electrode stripe by the SiO ₂ insulating film 17 is shown. This is a semiconductor laser device having a good temperature characteristic in this oscillation wavelength range. Not essential in providing. That is, the current confinement structure may be the structure of a conventionally used semiconductor laser device applied to a CdZnMgSe material.

In the double hetero structure semiconductor laser device of this embodiment, the bulk CdZnMg is used as the active layer.
Although Se was used, if a single or multiple quantum well structure composed of CdZnMgSe material was used instead,
Laser oscillation at a higher temperature is possible.

In this case, the quantum well layer formed of a thin film having a thickness of about 10 nm or less and the quantum barrier layer separating the quantum well layer do not necessarily need to be lattice-matched with the p-type InP substrate 11, and in this case, the operation by the strained quantum well is performed. The effect of reducing the current appeared. Further, even in the case of the double hetero structure, lattice mismatch of the active layer is allowed as long as the problem of deterioration due to current injection is suppressed. FIG. 5 shows the third aspect of the present invention.
3 is a cross-sectional view showing a schematic structure of a double hetero structure light emitting diode device according to the embodiment of FIG.

In the figure, reference numeral 21 denotes a p-type InP substrate. On the p-type InP substrate 21, a thickness of 200 nm,
P-type CdZnMgSe with a carrier concentration of 2 × 10 ¹⁸ cm ⁻¹
Buffer layer 22, thickness 2 μm, carrier concentration 1 × 10 ¹⁸
cm ⁻¹ p-type CdZnMgSe cladding layer 23, thickness 3
00 nm undoped CdZnMgSe active layer 24, n-type CdZnMg with a thickness of 5 μm and carrier concentration of 1 × 10 ^18.
Se clad layer 25, thickness 200 nm, carrier concentration 5
A × 10 ¹⁸ n-type CdZnMgSe contact layer 26 is sequentially formed. Then, n is formed on the n-type CdZnMgSe contact layer 26 and the p-type InP substrate 21, respectively.
A side electrode 27 and a p-type electrode 28 are provided.

Here, the undoped CdZnMgSe active layer 24, the p-type CdZnMgSe clad layer 23, and n.
The lattice constant of the CdZnMgSe cladding layer 25 is p-type I.
Almost the same as the nP substrate 21, and undoped CdZnMgS
The band gap of the active layer 24 is p-type CdZnMgSe
The undoped CdZnMgSe active layer 24 and the p-type CdZnMgSe are made smaller than the band gaps of the clad layer 23 and the n-type CdZnMgSe clad layer 25.
The composition of Cd, Zn and Mg of the cladding layer 23 and the n-type CdZnMgSe cladding layer 25 is set.

In addition, the p-type CdZnMgSe buffer layer 2
2 has a lattice constant substantially equal to that of the p-type InP substrate 21, and its band gap is p-type CdZnMgSe clad layer 23.
P-type CdZn to be smaller than the band gap of
The composition of Cd, Zn and Mg of the MgSe buffer layer 22 is set.

Further, the lattice constant of the n-type CdZnMgSe contact layer 26 is almost equal to that of the p-type InP substrate 21, and the band gap thereof is the n-type CdZnMgSe cladding layer 2.
N-type CdZ so as to be smaller than the band gap of 5
The composition of Cd, Zn and Mg of the nMgSe contact layer 26 is set. It is desirable that the active layer, the clad layer, and the like made of such a CdZnMgSe layer be formed by a molecular beam epitaxy method.

In the double heterostructure semiconductor device having the structure shown in this embodiment, the band gap of the undoped CdZnMgSe active layer 24 is 2.65 eV, and the p-type CdZn is formed.
The band gaps of the MgSe clad layer 23 and the n-type CdZnMgSe clad layer 25 are both 2.80 eV, the band gap of the p-type CdZnMgSe buffer layer 22 is 2.00 eV, and the n-type CdZnMgSe contact layer 26.
The current injection emission characteristics of the double-heterostructure light emitting diode device in which the band gap was set to 2.00 eV, the n-side electrode 27 was circular with a diameter of 150 μm, and was scraped to about 300 μm × 300 μm at room temperature.

As a result, the emission wavelength at an operating current of 20 mA is 470 nm, and the operating voltage at this time is 2.6 V.
Met. Light emission intensity is 1 by resin molding
High-luminance light emission higher than that of candela was obtained. That is, by adopting this element structure, a highly efficient blue light-emitting double heterostructure diode device, which was difficult in the past, was obtained.

The reason why such good emission characteristics are obtained is that the use of p-type InP as the substrate reduces the hetero barrier against the p-type clad layer p-type CdZnMgSe and suppresses the operating voltage. It depends on what I was able to do.
Also, all CdZnMgSe layers are lattice matched to the substrate,
Moreover, since the group VI element is one kind of Se, a good crystal without defects such as dislocation can be produced.

In the double heterostructure light emitting diode device having the structure shown in this embodiment, the undoped CdZ is used.
The bandgap energy of the nMgSe active layer 24 is C
The emission wavelength at room temperature could be changed from 630 nm to 400 nm by changing the composition of d, Zn and Mg.

Although the light emitting diode device having the double hetero structure has been described in the present embodiment, this is important in order to obtain particularly high luminous efficiency, but such a structure is not always necessary.

That is, C having the same band gap
A pn junction formed of dZnMgSe on the p-type InP substrate 21 or a so-called single heterojunction which is a pn junction in which the band gap of one CdZnMgSe is larger than the other may be used. At this time, the light emitting efficiency is remarkably improved by forming the material on the surface side having the electrode on the side opposite to the substrate through which light is extracted so as to be transparent with respect to the emission wavelength. The present invention is not limited to the above-described embodiments, and for example, the conductivity types of the semiconductor layers of the semiconductor light emitting device of the above embodiments may be reversed.

Regarding the current confinement structure and the light guide structure in the semiconductor laser device and the current diffusion structure and the light extraction structure in the light emitting diode device,
The present invention is not limited to the above embodiment. In addition, various modifications can be made without departing from the scope of the present invention.

[0074]

As described above in detail, according to the present invention, InP is used as the semiconductor substrate, and the light emitting semiconductor layer and the semiconductor layer for confining light and electrons are used as II-
By using CdZnMgSe among Group VI compound semiconductors, a practical semiconductor light emitting device having a low operating voltage and a small operating current can be realized.

[Brief description of drawings]

FIG. 1 is a sectional view showing a main part structure of a double hetero structure semiconductor laser device according to a first embodiment of the present invention.

FIG. 2 is a band diagram of a substrate and a p-type cladding layer of the double hetero structure semiconductor laser device of FIG.

FIG. 3 is a sectional view showing a main structure of a double hetero structure semiconductor laser device according to a second embodiment of the present invention.

4 is a band diagram of a substrate and a buffer layer of the double hetero structure semiconductor laser device of FIG.

FIG. 5 is a sectional view showing a main structure of a double hetero structure light emitting diode device according to a third embodiment of the present invention.

FIG. 6 is a cross-sectional view showing a main structure of a semiconductor laser device using a conventional II-VI group compound semiconductor.

FIG. 7 is a sectional view showing a main structure of a light emitting diode device using a conventional II-VI group compound semiconductor.

FIG. 8 is a band diagram for explaining problems of a semiconductor light emitting device using a conventional II-VI group compound semiconductor.

FIG. 9 is a sectional view showing a main part structure of another semiconductor laser device using a conventional II-VI group compound semiconductor.

[Explanation of symbols]

1 ... p-type InP substrate 2 ... p-type CdZnMgSe cladding layer 3 ... undoped CdZnMgSe active layer 4 ... n-type CdZnMgSe cladding layer 5 ... SiO ₂ insulating film 6 ... n-side electrode 7 ... p-side electrode 11 ... p-type InP substrate 12 ... p-type CdZnMgSe buffer layer 13 p-type CdZnMgSe clad layer 14 undoped CdZnMgSe active layer 15 n-type CdZnMgSe clad layer 16 n-type CdZnMgSe contact layer 17 SiO ₂ insulating film 18 n-side electrode 19 p-side electrode 21 p-type InP substrate 22 ... p-type CdZnMgSe buffer layer 23 ... p-type CdZnMgSe clad layer 24 ... undoped CdZnMgSe active layer 25 ... n-type CdZnMgSeSe clad layer 26 ... n-type CdZnMgSe contact layer 27 ... n-side electrode 28 ... p-side electrode

Claims (2)

[Claims] 1. A semiconductor substrate made of InP and Cd _1-xy Zn _x Mg _y formed on the semiconductor substrate.
A semiconductor light emitting device comprising Se (0 ≦ x ≦ 1, 0 ≦ y ≦ 1) and a light emitting semiconductor layer that emits light by current injection. 2. A semiconductor substrate made of InP, and Cd _{1 -uv} Zn _u Mg _v formed on the semiconductor substrate.
A first conductivity type cladding layer made of Se (0 ≦ u ≦ 1, 0 ≦ v ≦ 1), and Cd _{1 -wx} Z formed on the first conductivity type cladding layer.
n _w Mg _x Se (0 ≦ w ≦ 1, 0 ≦ x ≦ 1), which emits light by current injection, and a Cd _{1 -yz} Zn _y Mg formed on the light emitting semiconductor layer.
A semiconductor light emitting device comprising a second conductivity type cladding layer made of _z Se (0 ≦ y ≦ 1, 0 ≦ z ≦ 1).