JP2540229B2 - Compound semiconductor light emitting device - Google Patents

Description

The present invention relates to a compound semiconductor light emitting device, and particularly to ZnSe,
The present invention relates to a structure of a high brightness blue and ultraviolet light emitting device using ZnSSe as a light emitting layer.

(B) Prior art II-VI group compound semiconductor ZnSe is a direct transition type semiconductor with a forbidden band width of 2.7 eV at room temperature. It has high brightness and short wavelength including blue light emitting diode and laser using this ZnSe. Research and development of light emitting devices are underway. Also, ZnSSe
Is a mixed crystal of ZnSe and ZnS (forbidden band width: 3.7 eV), and the forbidden band width increases as the composition ratio of ZnS increases, and emission of shorter wavelengths from blue to ultraviolet can be obtained.

A conventional example of a short-wavelength light emitting device using these materials
Shown in the figure. This device is a so-called pn junction type ZnSe blue light emitting device. In the figure, 71 is a Si-doped n-type GaAs short crystal substrate, 72 is a Ga-doped n-type ZnSe light emitting layer, and 73 is a 0-doped p-type ZnSe.
The light emitting layer, 74 is a positive electrode, and 75 is a negative electrode. The light emitting layers 72 and 73 made of two epitaxial ZnSe layers are heteroepitaxially grown directly on the GaAs substrate 71 by the MBE method. The electrode is a positive electrode 74 formed by depositing Au on the p-type ZnSe light emitting layer 73.
Is formed, and the negative electrode using In is formed on the back surface of the GaAs substrate 71.
75 are formed. The pn junction type Zn fabricated in this way
Se blue light emitting element is 4 at low temperature of liquid nitrogen (77K).
Blue emission having a peak wavelength at 40 nm is obtained. However, it is known that it shows almost no luminescence at room temperature (Japan.J.Appl.Phys.21 (1989) L200.
1.K.Akimoto et.al.).

(C) Problems to be Solved by the Invention As described above, the conventional ZnSe adolescent light-emitting device cannot obtain sufficient emission brightness at room temperature. This is because the ZnSe light emitting layer is not epitaxially grown on a GaAs substrate and does not have sufficient quality suitable for the light emitting layer. That is, when ZnSe is heteroepitaxially grown on a GaAs substrate, lattice defects are generated due to lattice mismatch between GaAs and ZnSe or mismatch of thermal expansion coefficient.
There has been a problem that it is extremely difficult to obtain a Znse layer of high quality and high purity due to thermal diffusion of Ga and As from the GaAs substrate to the ZnSe epitaxial layer. Furthermore, GaAs has a small forbidden band width of about 1.4 eV and absorbs light having a wavelength of about 880 nm or less. Therefore, when GaAs is used as the substrate, there is a problem that the blue light emitted from the light emitting layer cannot be efficiently extracted to the outside of the device.

(D) Means for Solving the Problems The present invention has been made in view of the above point, in which a light emitting element layer including a semiconductor epitaxial layer is stacked on a single crystal substrate, and a voltage is applied to the light emitting element layer. A compound semiconductor light-emitting device having at least one pair of electrodes for performing the operation, wherein the single crystal substrate is ZnS or ZnSSe,
The light emitting layer provided in the light emitting element layer is made of ZnZe,
A light emitting layer is formed between the light emitting layer and the single crystal substrate.
A compound semiconductor light emitting device, characterized in that a CdZnS conductive layer having a composition lattice-matched with ZnSe is provided.

Alternatively, it is a compound semiconductor light emitting device in which a light emitting device layer made of a semiconductor epitaxial layer is laminated on a single crystal substrate, and at least one pair of electrodes for applying a voltage to the light emitting device layer is provided. Crystal substrate is ZnS
Or ZnSSe, the light-emitting layer provided in the light-emitting element layer is made of ZnSSe, CdZnS conductive layer having a composition lattice-matched with ZnSSe constituting the light-emitting layer between the light-emitting layer and the single crystal substrate The compound semiconductor light emitting device is characterized by being provided with.

Furthermore, in the compound semiconductor light emitting device having the ZnSe or ZnSSe as the light emitting layer, a CdS-ZnS strained superlattice layer or a ZnS-ZnSe strained superlattice layer between the CdZnS conductive layer and the ZnS or ZnSSe single crystal substrate, or, A compound semiconductor light emitting device is characterized in that a CdZnS layer or a ZnSSe layer having a composition ratio having an intermediate lattice constant between the CdZnS conductive layer and ZnS or ZnSSe forming the substrate is provided.

More specifically, the present invention is characterized in that all semiconductor components from the single crystal substrate to the compound semiconductor light emitting layer are formed of II-VI group compound semiconductors. Further, the semiconductor portion other than the light emitting layer is characterized by being composed of a II-VI group compound semiconductor having a forbidden band width larger than that of the light emitting layer so as to have a high light transmittance for light emission.

The single crystal substrate in this invention is the same as the light emitting layer II
ZnS, which is a group VI compound semiconductor, has a wider band gap than the light emitting layer, and has a high light transmittance for blue light emission.
Alternatively, a ZnSSe single crystal substrate is used. As this ZnS, ZnSSe single crystal, a halogen chemical transport method, a sublimation method, a bulk single crystal grown by a high-pressure melting method or the like can be used,
Of these, ZnS or ZnSSe bulk single crystals grown by the halogen transport method using iodine as a transport medium are particularly excellent as a substrate for epitaxial growth with a low dislocation density (etch pit density of 10 ⁴ cm ^-2 or less), and for blue emission. 90
It is preferable because it has a high light transmittance of at least 100% (in the case of ZnS). When ZnSSe is used as the substrate, its S composition should be 1
It is preferably from 00 to 30 atom%. When the S composition has a lower concentration than this, the light transmittance for blue emission is lowered.

Next, the CdZnS conductive layer provided between the ZnSe or ZnSSe issuing layer and the ZnS or ZnSSe single crystal substrate is characterized by having the same lattice constant as ZnSe or ZnSSe forming the issuing layer. CdZnS is a mixed crystal semiconductor of CdS and ZnS, and its lattice constant and band gap depend on its composition.
It changes between 5.83Å and 2.42eV of ZnS and 5.42Å and 3.68eV of ZnS. Comparing this property with the case of ZnSSe which is a mixed crystal semiconductor of ZnSe and ZnS, it has a feature that it has a larger forbidden band width than ZnSSe when the lattice constant is the same. The difference in the forbidden band width is the difference between ZnSe and CdZnS (Zn composition 61
Atomic%) is about 0.19eV. Therefore, CdZn having the same lattice constant as the light emitting layer (ZnS or ZnSSe)
If S is used for the conductive layer, it becomes possible to have high transmittance for light emission without inducing lattice defects due to lattice mismatch. In addition, the light emitting layer (ZnSe or Zn
It is known that an energy barrier is formed mainly in the valence band at the junction between the light emitting layer and the conductive layer due to the difference in the forbidden band width between the SSe) and the conductive layer (CdZnS). The effect of confining carriers (electrons) in the interior makes it possible to increase the luminous efficiency.

A low resistance n-type CdZnS layer is used as this conductive layer, and its resistivity is 10 ^-2 to 10 ^-1 Ω to keep the element resistance low.
The thickness is preferably about cm and the film thickness is about 1 to 10 μm.

Furthermore, a CdS-ZnS strained superlattice layer or a ZnSe-ZnS strained superlattice layer can be inserted between the CdZnS conductive layer and the substrate as a means for relaxing the lattice mismatch between the light emitting layer and the substrate. The film thickness of each superlattice is 20-100Å,
The repetition cycle is preferably 5 to 100 cycles. Furthermore, as a similar means, between the CdZnS conductive layer and the substrate, a CdZnS conductive layer and a CdZnS layer or Z having a lattice constant intermediate between ZnS and ZnSe forming the substrate are formed.
An nSSe layer can be inserted. By inserting the strained superlattice layer or mixed crystal layer between the CdZnS conductive layer and the substrate in this way, the lattice mismatch between the substrate and the conductive layer (light emitting layer) is relaxed, and the transition due to the lattice relaxation occurs. Propagation can be suppressed, and a high-quality ZnSe or ZnSSe light emitting layer can be obtained.

(E) Action As described above, according to the present invention, all semiconductor components from the single crystal substrate to the compound semiconductor light emitting layer are II
Formed of a II-VI compound semiconductor, and the semiconductor portion other than the light-emitting layer is composed of a II-VI compound semiconductor having a larger forbidden band width than that of the light-emitting layer so as to have high light transmittance for light emission. By doing so, it is possible to obtain a high-purity, high-quality ZnSe or ZnSSe light-emitting layer, and it is also possible to efficiently extract light emission to the outside of the device, and to manufacture a high-brightness ZnSe, ZnSSe blue, ultraviolet light-emitting device. It has become possible.

(F) Examples Next, the present invention will be described based on Examples.

Example 1 FIG. 1 shows a schematic cross-sectional view of a ZnSepn junction type blue light emitting device which is a first example of the present invention. In the figure, 1 is ZnS
Single crystal substrate, 2 CdS-ZnS strained superlattice layer, 3 low resistance n-type
CdZnS conductive layer, 4 n-type ZnSe light emitting layer, 5 p-type ZnSe light emitting layer, 6 p-type ZnSe conductive layer, 7 positive electrode, 8 negative electrode, 9,
10 is a lead wire.

As the ZnS substrate 1, for example, a bulk single crystal prepared by an iodine transport method is cut out and polished (100) or (1
10) A ZnS single crystal substrate wafer was used. On this ZnS single crystal substrate 1, a CdS-ZnS strained superlattice layer 2, a low resistance n-type CdZnS conductive layer 3 and a pn junction type ZnSe light emitting layer 4 and 5, a p-type
The ZnSe conductive layer 6 was sequentially grown by the MBE method. When MBE is grown, Cd, Zn, S, and Se are used as raw material molecular beam sources.
The substrate temperature was set to 300 ° C. The substrate temperature is preferably set in the range of 200 to 300 ° C. in order to grow a high quality epitaxial layer at an appropriate growth rate of about 1 μm / h. The CdS-ZnS strained superlattice layer 2 is inserted in order to relax the lattice mismatch between the ZnS substrate 1 and the CdZnS conductive layer 3, and the film thickness of each superlattice layer has an average composition. The CdS layer is made to be almost equal to CdZnS forming the conductive layer 3.
Å, ZnS layer was set to 60 Å. The number of repetition cycles is 5
It was set to 0 cycle. The molecular beam intensity during growth of the CdS layer and ZnS layer is 1 × the molecular beam intensity of Cd and Zn.
And 10 ^-6 Torr, molecular beam intensity of S was kept constant at 5 × 10 ^-6 Torr. The Zn composition of the low resistance n-type CdZnS conductive layer 3 was set to 61 atomic% in order to lattice-match with the ZnSe light emitting layer. Cd and Zn
The composition ratio of was controlled by the molecular beam intensity ratio of Cd and Zn, and was set to 3.9 × 10 ⁻⁷ Torr and 6.1 × 10 ⁻⁷ Torr, respectively. The S molecular beam intensity was 5 × 10 ⁻⁶ Torr. Al was added as an impurity in order to obtain a low resistance n-type CdZnS layer suitable as a conductive layer. By setting the molecular beam intensity of Al to 1 × 10 ^-9 Torr,
A low resistance n-type CdZnS film having an Al concentration of 2 × 10 ¹⁹ cm ⁻³ (carrier concentration of 1 × 10 ¹⁹ cm ⁻³ , resistivity of 10 ⁻² Ω · cm) could be obtained. The film thickness was 2 μm.

Three epitaxial layers made of ZnSe are sequentially laminated on the conductive layer 3 as an n-type ZnSe light emitting layer 4, a p-type ZnSe light emitting layer 5, and a p-type ZnSe conductive layer 6. These 3 were grown with a Zn molecular beam intensity of 1 × 10 ⁻⁶ Torr and a Se molecular beam intensity of 1 × 10 ⁻⁶ Torr,
The same Al as that of the CdZnS conductive layer 3 was used as the n-type impurity for the n-type ZnSe light emitting layer 4, and the addition concentration thereof was 5 × 10 ¹⁷ cm ⁻³ . The Al molecular beam intensity during growth was set to 5 × 10 ^-11 Torr. The film thickness is 1 μm. To the p-type ZnSe light emitting layer 5, 1 × 10 ¹⁹ cm ⁻³ of Li was added as a p-type impurity. The Li molecular beam intensity during growth was set to 2 × 10 ^-9 Torr. The film thickness is 0.2 μm. p-type ZnS
The conductive layer 6 had a Li concentration of 5 × 10 ¹⁹ cm ⁻³ (Li molecular beam intensity was 1 × 10 ⁻⁸ Torr) and a film thickness of 0.5 μm. After forming these epitaxial layers 4, 5 and 6, Au is vapor-deposited on the p-type ZnSe conductive layer 6 and heat treated in N ₂ gas at 200 ° C. for several seconds to several minutes to form an ohmic positive electrode 7. , P-type ZnSe
A portion of the conductive layer 6 where the positive electrode 7 is formed is masked with a photoresist or the like, and a part of the epitaxial layers 4, 5 and 6 and one of the n-type CdZnS conductive layers 3 are formed by reactive ion etching (RIE) using CF _4. The surface of the portion was etched to expose the low resistance n-type CdZnS conductive layer 3, and In and Al were sequentially deposited on the surface to form an ohmic negative electrode 8. After removing the photoresist,
The lead wires 8 and 9 were connected to each other to fabricate a pn connection type Znse blue light emitting device.

The ZnSe blue light-emitting device produced in this manner exhibits good rectification characteristics with a rising voltage of 1.5 V in current-voltage characteristics, a driving voltage of 2 V and a driving current of 10 mA, and a peak wavelength of 460 nm, a half-value width of 25 nm, and an emission luminance at room temperature. It was possible to obtain a high brightness blue light emission of 20 mcd.

Example 2 FIG. 2 shows a schematic sectional view of a ZnS Sepn junction type blue light emitting device which is a second example of the present invention. In the figure, 1 is Zn
S single crystal substrate, 12 CdS-ZnS strained superlattice layer, 13 low resistance n
Type CdZnS conductive layer, 14 n-type ZnSSe light emitting layer, 15 p-type ZnSSe
A light emitting layer, 16 is a p-type ZnSSe conductive layer, 7 is a positive electrode, 8 is a negative electrode, and 9 and 10 are lead wires. In this ZnS Sepn junction type blue light emitting device, the substrate 1 is a ZnS single crystal substrate similar to that of Example 1, and the basic epitaxial layers 12, 13, 14, 15, 16 of the five layers on the ZnS substrate 1 are the same. The structure is the same as in Example 1, but the light emitting layer is composed of ZnSSe, and accordingly, the layer thickness ratio between the CdS layer and the ZnS layer of the CdS-ZnS strained superlattice layer 12 and the low resistance n-type The composition of the CdZn conductive layer 14 is changed. By forming the light emitting layer of ZnSSe, the emission wavelength can be made shorter than that of the case of using ZnSe. In this example, the S composition was 200 atomic%. Each epitaxial layer was formed by the MBE method as in Example 1.

The Al concentration and film thickness of the low resistance n-type CdZnS conductive layer 13 provided between the ZnSSe light emitting layers 14 and 15 and the ZnS substrate 1 are the same as those in Example 1, but lattice matching with the ZnSSe light emitting layer is taken. Therefore, its S composition is set to 49 atom%. To obtain the above Zn composition
The molecular beam intensities of Cd and Zn are 5.1 × 10 ^-7 Torr and 4.9, respectively.
It was set to × 10 ^-7 Torr.

The thickness of the CdS-ZnS strained superlattice layer 12 was set to 40 Å for the CdS layer and 40 Å for the ZnS layer so that the average lattice constant of the CdS-ZnS strained superlattice layer 12 was about the same as that of the ZnSSe light emitting layers 14 and 15 and the CdZnS conductive layer 13. The repetition period of the superlattice was 60 periods. n-type light emitting layer
When growing 14, the p-type light emitting layer 15, and the p-type same electric layer 16, Z
The molecular beam intensities of n, S, and Se are 1 × 10 ⁻⁶ Torr and 2 respectively.
× S composition ratio 20 With ^{10 -6 Torr, 1 × 10 -6} Torr
An atomic% ZnSSe epitaxial layer was obtained. For the n-type ZnSSe light emitting layer 14, 5 × 10 ¹⁷ cm ⁻³ of Al was added and the film thickness was set to 1 μm.
Li was added to the p-type ZnSSe light emitting layer 15 and the p-type ZnSSe conductive layer 16 at 1 × 10 ¹⁹ cm ⁻³ and 5 × 10 ¹⁹ cm ⁻³ , respectively, and the film thickness was 0.2 μm and 0.5 μm, respectively. After forming each epitaxial layer, electrodes were formed and lead wires were connected in the same manner as in Example 1 to fabricate a ZnSSe pn junction type light emitting device.

The ZnSSe light-emitting device produced in this manner exhibits a 1.7 V rising voltage in terms of current-voltage characteristics, a driving voltage of 2.2 V at room temperature, a driving current of 12 mA, an emission peak wavelength of 430 nm, a half-value width of 30 nm, and a high luminance of 20 mcd. It was possible to obtain blue-violet emission.

Example 3 FIG. 3 shows a schematic sectional view of a ZnSepn junction type blue light emitting device according to a third example of the present invention. In the figure, 1 is a ZnS single crystal substrate, 22 is a ZnS-ZnSe strained superlattice layer, and 3 is a low resistance n-type C
dZnS conductive layer, 4 n-type ZnSe light emitting layer, 5 p-type ZnSe light emitting layer, 6 p-type ZnSe conductive layer, 7 positive electrode, 8 negative electrode, 9,
10 is a lead wire.

In this embodiment, all parts except the ZnS-ZnSe strained superlattice layer 22 have the same configuration and manufacturing method as the ZnSepn junction type blue light emitting device of the first embodiment, and the ZnS substrate 1 and the CdZnS conductive layer 3 or the ZnSe light emission. Instead of the CdS-ZnS strained superlattice layer, a ZnS-ZnSe strained superlattice layer 22 is used as a layer for relaxing lattice mismatch between the layers 4 and 5.

The layer thickness configuration of the strained superlattice layer 22 is such that the average lattice constant of the ZnS-ZnSe strained superlattice layer 22 is an intermediate value between the lattice constant of the ZnS substrate 1 and the lattice constant of the CdZnS conductive layer 3. Then 3
0 Å, 30 Å for ZnSe layer, and the number of repetition cycles was 50 so that lattice relaxation could be sufficiently performed.

The ZnSepn junction type blue light emitting device of this example also had the same device characteristics as in Example 1 and was able to obtain blue light emission with high brightness.

Example 4 FIG. 4 shows a schematic sectional view of a ZnSepn junction type blue light emitting device which is a fourth example of the present invention.

In the figure, 1 is a ZnS single crystal substrate, 32 is a ZnSSe lattice relaxation layer, 3 is a low resistance n-type CdZnS conductive layer, 4 is an n-type ZnSe light emitting layer, 5 is a p-type ZnSe light emitting layer, and 6 is a p-type ZnSe conductive layer. Layers, 7 is a positive electrode, 8 is a negative electrode, and 9 and 10 are lead wires.

In this embodiment, all parts except the ZnS-ZnSe strained superlattice layer 22 have the same configuration and manufacturing method as the ZnSepn junction type blue light emitting device of the first embodiment, and the ZnS substrate 1 and the CdZnS substrate.
A ZnSSe lattice relaxation layer 32 is used instead of the CdS-ZnS strained superlattice layer as a relaxation layer for lattice mismatch with the conductive layer 3 or the ZnSe light emitting layers 4 and 5. Zn forming the lattice relaxation layer 32
It is preferable that the SSe has a composition having a lattice constant intermediate between that of the ZnS substrate 1 and the CdZnS conductive layer 3. In this embodiment, the S composition thereof is 50 atom%. Zn with S composition of 50 atom%
To obtain the SSe layer, the Zn molecular beam intensity was set to 1 × 10 during MBE growth.
^-6 Torr, S and Se molecular beam intensities of 5 × 10
^-6 Torr and 1 x 10 ^-6 Torr were set. The film thickness was 3 μm.

The ZnSepn junction type blue light emitting device produced in this manner exhibited the same device characteristics as in Example 1 and was able to obtain blue light of high brightness.

Example 5 FIG. 5 shows a schematic sectional view of a ZnSepn junction type blue light emitting device of a fifth example of the present invention.

In the figure, 1 is a ZnS single crystal substrate, 42 is a CdZnS lattice relaxation layer, 3 is a low resistance n-type CdZnS conductive layer, 4 is an n-type ZnSe light emitting layer, 5 is a p-type ZnSe light emitting layer, and 6 is a p-type ZnSe conductive layer. Layers, 7 is a positive electrode, 8 is a negative electrode, and 9 and 10 are lead wires.

In this embodiment, all parts except the CdZnS lattice relaxation layer 42 have the same structure and manufacturing method as the ZnSepn junction type blue light emitting device of the first embodiment, and the ZnS substrate 1 and the CdZnS conductive layer 3 or the ZnSe light emitting layer 4 are used. CdS-ZnS strained superlattice layer instead of CdZ-ZnS strained superlattice layer
2 is used. The CdZnS layer forming the lattice relaxation layer 42 preferably has a lattice constant between the ZnS substrate 1 and the CdZnS conductive layer 3. In the present embodiment, the Zn composition of the CdZnS lattice relaxation layer 42 is set to 30 atomic%. Set. The thickness of the CdZnS lattice relaxation layer 42 was 1 μm. Used as the lattice relaxation layer 42
The CdZnS layer with a Zn composition of 30 atomic% has a narrower bandgap than ZnSe forming the light emitting layer and has a thickness of 1 for absorbing blue light emission.
It is preferable that the thickness is less than μm.

The znSepn junction type blue light emitting device produced in this manner showed the same good rectification characteristics as in Example 1. Regarding the emission brightness, the emission extraction efficiency due to absorption in the CdZnS lattice relaxation layer 42 decreases, but at room temperature the drive voltage 2
It was possible to obtain a blue light emission of 20 mcd at V and a driving current of 10 mA.

Example 6 FIG. 6 shows a schematic sectional view of a ZnSepn junction type blue light emitting device according to a sixth example of the present invention in FIG. In the figure, 51 is
ZnSSe single crystal substrate, 2 CdS-ZnS strained superlattice layer, 3 low resistance n-type CdZnS conductive layer, 4 n-type ZnSe light emitting layer, 5 p-type ZnS
e is a light emitting layer, 6 is a p-type ZnSe conductive layer, 7 is a positive electrode, 8 is a negative electrode, and 9 and 10 are lead wires.

In the present embodiment, the other parts except the ZnSSe single crystal substrate 51 have the same structure as the ZnSepn junction type blue light emitting device of the first embodiment,
It depends on the manufacturing method. As the single crystal substrate 51, a ZnSSe single crystal substrate having an S composition of 50 atomic% prepared by the iodine transport method is used. ZnSSe bulk single crystal prepared by iodine transport method has a high light transmittance (about 90%) for blue light emission in the S composition range of 100 to 30 atomic%, and is used as a single crystal substrate for a ZnSe blue light emitting device. be able to. Furthermore, ZnS
It is preferable because the lattice mismatch with the CdZnS conductive layer 3 or the ZnSe light emitting layers 4 and 5 can be reduced as compared with the case of using a single crystal substrate.

Also in this example, it was possible to obtain blue light emission with high brightness as in the ZnSe blue light emitting device of Example 1.

Example 7 FIG. 7 shows a schematic sectional view of a ZnSepn junction type blue light emitting device according to a seventh example of the present invention. In the figure, 61 is a low resistance n-type ZnS single crystal substrate, 62 is an n-type low resistance CdS-ZnS strained superlattice layer, 3 is a low resistance n-type CdZnS conductive layer, 4 is an n-type ZnSe light emitting layer, and 5 is p. Type ZnSe light emitting layer, 6 is a p-type ZnSe conductive layer, 67 is a positive electrode, 68 is a negative electrode, and 9 and 10 are lead wires. In the present embodiment, the single crystal substrate 61 is, for example, a molten Zn obtained by adding 10% by weight of Al to ZnS bulk single crystal prepared by an iodine transport method.
A low-resistivity n-type ZnS substrate wafer was cut out from an n-type ZnS single crystal having a resistivity of 10 Ω · cm and reduced in resistance by heat treatment at 1000 ° C. for 10 to 100 hours. The four epitaxial layers 3, 4, 5 and 6 except the n-type CdS-ZnS strained superlattice layer 62 on the n-type ZnS substrate 61 were formed in the same manner as in Example 1.
The thickness of the n-type CdS-ZnS strained superlattice layer 62 and the number of repetition periods were set in the same manner as in Example 1. However, since the device current has a structure flowing in this strained superlattice layer, Al is used as an n-type impurity. Resistivity of 5 × 10 ^-2 Ω ・ cm by adding 5 × 10 ¹⁸ cm ^-3
Of low resistance n-type conductive layer. The positive electrode 67 was formed by vapor-depositing Au on the p-type ZnSe conductive layer 6, and the negative electrode 68 was formed by using In on the back surface of the n-type ZnS single crystal substrate.

The ZnSepn junction type blue light emitting device manufactured in this manner was able to obtain blue light emission with high brightness as in the above-mentioned Examples.

(G) Effects of the Invention As described above, according to the present invention, it is possible to produce a high-intensity blue and ultraviolet light emitting device having ZnS or ZnSSe as a light emitting layer, and various display devices including a full color display device. It is extremely promising as a light source for various optoelectronics, such as a light source for light, a light source for high-density information processing, a light source for photochemical reaction processing, and the like.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing a ZnSepn junction type blue light emitting device according to a first embodiment of the present invention, and FIG. 2 is a schematic sectional view showing a ZnS Sepn junction type blue-violet light emitting device according to a second embodiment, 3 to 7 are schematic sectional views showing a blue light emitting device of ZnSepn junction type which is a third to a seventh embodiment of the present invention, respectively.
FIG. 8 is a schematic sectional view showing a conventional ZnSepn junction blue light emitting device. 1 ... ZnS single crystal substrate, 2,12 ... CdS-ZnS strained superlattice layer, 3.13 ... Low resistance n-type CdZnS conductive layer, 4 ... n-type ZnSe light emitting layer, 5 ... p-type ZnSe light emitting layer, 6 …… p-type ZnSe conductive layer, 7,67,74 …… positive electrode, 8,68,75 …… negative electrode, 9.10 …… lead wire, 14 …… n-type ZnSSe light-emitting layer, 15 …… p-type ZnSSe Light emitting layer, 16 …… p type ZnSSe conductive layer, 22 …… ZnS-ZnSe strained superlattice layer, 32 …… ZnSSe lattice relaxation layer, 42 …… CdZnS lattice relaxation layer, 51 …… ZnSSe single crystal substrate, 61 …… Low resistance n-type ZnS single crystal substrate, 62 …… Low resistance n-type CdS-ZnS strained superlattice layer, 71 …… Si-added n-type GaAs single crystal substrate, 72 …… Ga-added n-type ZnSe light-emitting layer, 73 …… O-doped p-type ZnSe emission layer.

Claims (6)

(57) [Claims] 1. A compound semiconductor light emitting device comprising a light emitting device layer made of a semiconductor epitaxial layer laminated on a single crystal substrate, and at least one pair of electrodes for applying a voltage to the light emitting device layer. The single crystal substrate is ZnS or ZnSSe, the light emitting layer provided in the light emitting element layer is made of ZnSe, the composition lattice-matched with ZnSe constituting the light emitting layer between the light emitting layer and the single crystal substrate. With Cd
A compound semiconductor light emitting device having a ZnS conductive layer. 2. A compound semiconductor light emitting device comprising: a light emitting device layer made of a semiconductor epitaxial layer laminated on a single crystal substrate; and at least one pair of electrodes for applying a voltage to the light emitting device layer. The single crystal substrate is ZnS or ZnSSe, the light emitting layer provided in the light emitting element layer is made of ZnSSe, a composition lattice-matched with ZnSSe forming a light emitting layer between the light emitting layer and the single crystal substrate. A compound semiconductor light emitting device, characterized in that an SdZnS conductive layer having is provided. 3. A CdS-ZnC strained lattice layer is provided between the CdZnS conductive layer and a ZnS or ZnSSe single crystal substrate.
And the compound semiconductor light emitting device according to 2. 4. The compound semiconductor light emitting device according to claim 1, wherein a ZnS—ZnSe strained superlattice is provided between the CdZnS conductive layer and the ZnS or ZnSSe single crystal substrate. 5. The lattice constant of the CdZnS layer forming the conductive layer and the lattice constant of ZnS or ZnSSe forming the substrate are substantially between the CdZnS conductive layer and the ZnS or ZnSSe single crystal substrate. CdZn with a composition having an intermediate lattice constant
The compound semiconductor light emitting device according to claim 1 or 2, wherein an S layer is provided. 6. A lattice intermediate between the lattice constant of the CdZnS layer forming the conductive layer and the lattice constant of ZnS or ZnSSe forming the substrate between the CdZnS conductive layer and the ZnS or ZnSSe single crystal substrate. 3. The compound semiconductor light emitting device according to claim 1, further comprising a ZnSSe layer having a composition ratio having a constant.