JPH0227777A - Semiconductor light emitting element - Google Patents

Abstract

PURPOSE:To increase current injection amount by providing (ZnS)1-x-y-x(GazSe3)x(GaP)y(ZnSe)z light emitting layer and a current injection layer having larger band gap than that of the emitting layer in contact with lattice matching condition therewith. CONSTITUTION:(ZnS)1-x-y-z(Ga2Se3)x(GaP)y(ZnSe)z0<=x<1, 0<=z<1) light emitting layer 7 and a current injected layer 6 made of (ZnS)1-x'-y'-z'(Ga2Se3)x'(GaP)y'(ZnSe)z' (0<=x'<=1, 0<=y', 1, 0, z'<1) are provided in a semiconductor light emitting element. Thus, both have satisfactory lattice matching. Since the band gap of the layer 7 is smaller than that of the layer 6, the flow of the implanted carrier light emitting layer is disturbed, and the generated light is enclosed in the light emitting layer by the difference of the refractive index of the light emitting layer and the current injected layer.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a compound semiconductor light emitting device,
More specifically, the present invention relates to a semiconductor light emitting device that emits light in the short wavelength range of visible light to ultraviolet light.

(Prior Art) Semiconductor light-emitting devices that emit visible light at short wavelengths (blue) and have high luminous efficiency have conventionally been formed using Zn5e.

The basic structure is shown in FIG. 7. It has a Zn5e crystal substrate 1 and an insulating layer 2. Holes are injected from a semi-transparent metal electrode 3 through the insulating layer 2 into the Zn5e crystal 1, and electrons pass through the luminescent center. Recombines with and emits light. Here, the crystal substrate l
For example, a single crystal grown by a high-pressure melting method is cut into 11-thick wafers, mirror-polished, and then heat-treated in a Zn solution to give a specific resistance of 0.3 to 2 Ω·cm. As the insulating layer 2, a Stow layer with a thickness of 300 to 5000 layers is used.
The film is also used as an ohmic electrode 4 to the Zn5e substrate 1
n-Ga, Au with a thickness of 500 to 1000 as electrode 3
A vapor deposited film is used.

(Problem to be solved by the invention) In this structure, the problem is how to efficiently inject holes, which are minority carriers, and it often depends on the formation technique of the insulating layer 2. In particular, the formation of the insulating layer 2 In general, high luminous efficiency cannot be obtained if Zn5e is made using a very thin other compound such as Sing, and since the luminous energy of this luminescent energy is close to the band gap energy of Zn5e, self-absorption within the crystal increases. Luminous intensity decreases.

Furthermore, this structure has a problem in that it is not possible to form a waveguide structure as in the present invention, which will be described later.

For this reason, devices with this structure have the drawback of not being able to sufficiently increase the emission intensity, and up until now, the quantum efficiency has been 1.
Only up to 0% was obtained.

The present invention was proposed in order to improve the above-mentioned drawbacks, and its purpose is to provide a semiconductor light emitting device that can inject a large amount of current, has high luminous efficiency, and emits short wavelength visible light. .

(Means for Solving the Problems) In order to achieve the above object, the present invention provides (ZnS) +
-m-y-g(GazSez)g(GaP)y(ZnS
e) s (0≦x<1°0≦y<1.0<z<1) In contact with the light-emitting layer under lattice matching conditions, and having a larger band gap than the light-emitting layer (ZnS) +-c −y・-1(G
a1Se3) , (GaP) y・(ZnSe) w・
(0≦x'<1, 0≦y'<l, 0<z'<
The gist of the invention is a semiconductor light emitting device characterized by having a current injection layer consisting of (1).

(Function) Therefore, the present invention requires that (a) the device light-emitting part is composed of a light-emitting layer and a current injection layer, which have good lattice matching with each other, and (b) that the band gap of the light-emitting layer is Because it is smaller than the bandgap of the layer, the flow of injected carriers out of the light emitting layer is blocked, and the difference in refractive index between the light emitting layer and the current injection layer causes the generated light to be confined within the light emitting layer. It is something.

Compound, ZnS+ Ga1Se3. GaP, and Z
Since n5e has a zincblende crystal structure, it is almost entirely solid solution, (ZnS)+-x-y
-m(GazSez)x(GaP), (ZnSe)
−(0≦x<l, O≦y<l, o<z<1)y. Figure 1 shows the relationship between the lattice constant and bandgap energy on the (100) plane. As can be seen from this figure, by using the above-mentioned quaternary or quinary solid solution, the bandgap becomes different under perfect lattice matching conditions. It is possible to form a multilayer structure of materials and obtain a high-quality heterojunction structure.

As a single-crystal substrate, St and G have a zincblende crystal structure and can be easily manufactured into large, high-quality wafers.
When aP is used, (ZnS
) t-x-y-m(GazSez)x(GaP)y(
The ZnSfl)g layer can be formed under perfect lattice matching conditions including the substrate, and a particularly high quality heterojunction structure can be obtained.

In such a heterojunction structure, band gap discontinuity inevitably occurs at the interface due to the difference in band gap energy. This bandgap discontinuity acts as a barrier against the outflow of carriers from a semiconductor with a small bandgap.
+−x−r−*(cazse*)x(GaP) , (
It is characterized by using a good heterojunction of ZnSe)y for the light-emitting part, that is, the light-emitting layer and the current injection layer, and the band gap discontinuity prevents the flow of injected carriers to the outside of the light-emitting layer, so that light is emitted within the light-emitting layer. The physical basis is that the number of carriers that recombine increases.

Next, examples of the present invention will be described. It should be noted that the examples are merely illustrative, and within the scope of the spirit of the present invention,
It goes without saying that various changes and improvements can be made.

(Example 1) Fig. 2 is a diagram for explaining the first example of the semiconductor light emitting device of the present invention, and shows a cross section of the light emitting device.
Sixth plate 5 has a thickness of 5n (GaA Ss,)o, 5x
(ZnS)els(ZnSe)s,es current injection layer (cladding layer) 6 and 0.5n thick CGazSes)o,
56(ZnS)e, 4! (ZnSe). 0.3 light emitting layer 7 and electrodes 8, 9 for the current injection layer and the light emitting layer. The current injection layer is n-type and has low resistance, and the light emitting layer is high resistance. When a voltage of approximately 1 cm is applied with the electrode 9 on the positive side, carriers are injected into the light emitting layer 7 and the voltage of approximately 46 cm is applied.
00 people emit blue light. Although carriers also flow to the current injection layer 6, the band gap difference was 0.4 eV, the effect of band gap discontinuity reduced the reactive current, and light was emitted with high efficiency with an external quantum efficiency of 1%. Note that when the combination of different materials disclosed in the present invention is used for the light emitting layer and the current injection layer,
The refractive index of the current injection layer is lower than that of the light emitting layer, and it acts as a so-called cladding layer, making it possible to realize a waveguide structure that confines light, thereby increasing light emission efficiency.

(Example 2) FIG. 3 is a diagram illustrating a second example of the present invention. In FIG. 0, a 2n-thick (GagS
es)z, sg(ZnS)a, zy(ZnSe)e
, +4 first current injection layer (first cladding layer) 11, and (Gashes) *, so (
ZnS) *, xm (ZnSe) *, +! The light emitting layer 12 and the (GagSes)e with a thickness of 0.1n
, sw(ZnS)o, ow(ZnSe). 1. It has a second current injection layer (second cladding layer) 13 and electrodes 14 and 15 for both current injection layers 11 and 13. When voltage is applied with the electrode 15 on the positive side, carriers are injected into the light emitting layer 12 through the thin current injection layer 13.

In the structure of this example, there is band discontinuity on both sides of the light emitting layer, and carrier return can be reduced.

The resistance of the element is determined mostly by the high-resistance current injection layer 13. In the zero element, emitted light is guided between the current injection layers that act as cladding layers, and is emitted mainly in a direction parallel to the layers. The 0 emission wavelength is approximately 4600 blue,
An external quantum efficiency of 3% was obtained.

(Example 3) FIG. 4 is a diagram showing a third embodiment of the present invention.

In the figure, a 2n-thick (GaP
) @, 5s (ZnS) 6. zs (Zips)
A first current injection layer (first cladding layer) 19 having a composition of o, oq, and a (GaP) layer having a thickness of 0.3 ts.
@, 61 (ZnS) @, a, (ZnSe) @
, an O5 light-emitting layer 20, and a (GaP) layer with a thickness of 0.1 nm.
*, ss (ZnS) o, sg (ZnSe)
e, @T second current injection layer (second cladding layer) 21
and electrodes 22.23 for both current injection layers 19 and 21.
The structure of the 0 light emitting part having 0 is the same as in Example 2, and the 0 emission wavelength at which a remarkable improvement in luminous efficiency was obtained compared to the conventional light emitting element is about 4600 blue.

(Embodiment 4) FIG. 5 is a diagram for explaining the fourth embodiment of the present invention. In FIG.
*, sg (ZnS) *, 4m (ZnSe)
e, as first current injection layer (first cladding layer) 2
5, 0.3n thick (GaP)z, 5v(ZnS)z,
ow(ZnSe)z, ox light emitting layer 26, and further 0.
In thickness (GaP)z, 5i (ZnS)z, 4o(
ZnSe) o, am second current injection layer (second cladding layer) 27 and electrode 28 for current injection layer 25.27
．． He has 29 years of experience. Light is emitted by applying a voltage with the electrode 27 on the positive side, and the light is guided between both current injection layers and emitted. The emission wavelength of the above combination is approximately 520
0 green color, and an external quantum efficiency of 3% was obtained.

(Example 5) FIG. 6 is a diagram for explaining the fifth example of the present invention, which is for obtaining purple color (wavelength: 4100).

In the figure, a 2n thick (caus
es) o, +1 (ZnS) o, sg (ZnSe) o, a
*First current injection N (first cladding layer) 31, 0.
3n thick (GazSet) a, xq (ZnS) o
, sq (ZnSe) 6.04 light emitting layer 32, further 0.11 thick CGazSex) o, + 2 (Zn
S) 6. s + (ZnSe) @, (16 second current injection layer (second ground layer) 33, current injection layer 3
It has electrodes 34.35 to 1°33. Like Examples 2 to 4, the structure of this example also has a waveguide structure, so carriers and light are effectively confined, and guided light with high luminous efficiency is emitted in a direction parallel to the layer. be done.

(Effect of the invention) As described above, according to the present invention, (ZnS)+−m−y
-g(GamSes)y(GaP)y(ZnSe)-(
0≦x<1. O≦yku1, Q<Z<1) In contact with the light-emitting layer under lattice matching conditions, and having a larger band gap than the light-emitting layer (ZnS)+-r-y・-++・(GagSez)
By having a current injection layer consisting of z+ (GaP)r□ (ZnSe)z・(0≦χ9×1.0≦y'<l, Q<z'<l), a large amount of current can be injected, Moreover, it is possible to obtain a semiconductor light emitting device that emits short wavelength visible light from green to blue to violet and has high luminous efficiency.

[Brief explanation of the drawing]

Figure 1 shows (100) solid solutions of ■-■ group and ■~■ group compounds.
This shows the relationship between the lattice constant on the surface and the band gap energy. FIG. 2 schematically shows the structure of the first embodiment of the semiconductor light emitting device of the present invention, FIG. 3 shows the structure of the second embodiment of the present invention, and FIG. 4 shows the structure of the third embodiment of the present invention. 5 shows the structure of the fourth embodiment of the present invention, FIG. 6 shows the structure of the fifth embodiment of the present invention, and FIG. 7 shows the structure of a conventional light emitting device. . l ・ ・ ・ 2 ・ ・ ・ 3 ・ ・ ・ 4 ・ ・ 5.30・ 6 ・ ・ ・ 7 ・ ・ ・ 8, 9゜10, 16 11.13・ 12・ ・ 19.21・ 20・ ・・25, 27・ ・Zn5e substrate・Insulating layer・Semi-transparent metal electrode・Electrode・Si substrate-(GazSez)olg(ZnS)a, 1z(Zn
Se) a, as current injection layer - (GazSes) o, s & (ZnS) o, atc
Znse) o, ox light emitting layer 14, 15.22.23.28.29.34.35, electrode 24... GaP substrate' (GazSez)6. sq (ZnS)e, t
q (ZnSe)6. Ia current injection layer・(GazSes)s, 5o(ZnS)z, sq(
ZnSe) o, + as light emitting layer・(GaP) o, ss (ZnS) a, sq
(ZnSe) o, ov current injection layer/(GaP) o, ha (ZnS) e, t, (
ZnSe) o, as light-emitting layer/(GaP) o, s
x (ZnS) @, 4@ (ZnSe) s, a
m current injection layer 26 ... (GaP) a, sw (ZnS) +, o*
(ZnSe) o, oz light emitting layer 3133...(GaiSe
s) o, ++ (ZnS) o, a+ (ZnSe) a, ai
Current injection layer 32...(GatSes)+, 3. (ZnS)o,
5q(ZnSe)o, *a Emissive layer patent applicant Nippon Telegraph and Telephone Corporation Representative Patent attorney Satoshi Takayama Kai (1 other person) Fig. Flute Fig. 4 Fig. Fig. 6 Fig. Fig.

Claims (1)

[Claims] (ZnS)_1_-_x_-_y_-_z(Ga_2S
e_3)_x(GaP)_y(ZnSe)_z(0≦x
<1, 0≦y<1, 0<z<1), which is in contact with the light-emitting layer under lattice matching conditions and has a larger band gap than the light-emitting layer (
ZnS)_1_x'_-_y'_-_z'(Ga_2S
e_3)_x'(GaP)_y'(ZnSe)_z'(
1. A semiconductor light-emitting device comprising: a current injection layer where 0≦x′<1, 0≦y′<1, and 0<z′<1.