JPS6232665A - Light emitting element - Google Patents

Abstract

PURPOSE:To implement a blue light emitting element having excellent characteristics, by using a GaAs crystal, to which In is added, thereby growing a high quality ZnSe epitaxial single crystal thin film. CONSTITUTION:The grating constant of ZnSe is 5.6676-5.6687Angstrom at a room temperature. Meanwhile, that of GaAs of a III-V group semiconductor is 5.653Angstrom , and that of InAs is 6.058Angstrom . The GaAs and the InAs have a so-called homogeneous fusing form, which is capable of single crystallization at any rate. Therefore, the grating constant can take values between 5.653Angstrom and 6.058Angstrom depending on the rate between Ga and In. The crystals of In0.034Ga0.966As and In0.04Ga0.96As are used for a substrate, and a ZnSe single crystal thin film is epitaxially grown. As a result, the gratings are aligned and no dislocation is found in the substrate. Therefore the excellent thin film, whose crystal defect is very few, is obtained. In this way, a P-N junction is formed in the ZnSe epitaxial film, and the excellent light emitting element is obtained.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is directed to manufacturing a light-emitting element capable of emitting blue light by forming a high-quality epitaxial thin film of II-VI compound semiconductor Zn5e suitable for blue light emission. Zn is essential for
This is about a light-emitting device that uses a high-quality substrate crystal that is lattice-matched to 5e.

(Summary of the Invention) The present invention provides a light-emitting device that emits particularly blue light, which is epitaxially grown on a thin lao crystal substrate of a II-VI compound semiconductor consisting of elements belonging to group 1 and group 2 of the periodic table. In the element, Ink is added to the crystal substrate,
Or alloyed ■-■ group compound semiconductor crystal GaA
The purpose is to obtain a blue light-emitting element with high characteristics by using it in s'.

(Prior art and problems to be solved by the invention) Light emitting diode elements using compound semiconductors have been put into practical use using ■-V group compound semiconductors, but the emission wavelength ranges from 8 μm to 0.48 μm. So-called blue light emission (0
, 45-0.3 μm band) cannot be produced. These ■−
(2) Group II-VI compound semiconductors are known in place of compound semiconductor materials.

Zn5e is well known for blue light emission. In order to make this into a light emitting device, it is necessary to grow Zn5eo thin II epitaxially on a substrate crystal, but in this case, nine substrates are required to match the lattice constant of the Zn5e thin film. For this purpose, two methods can be considered: f4) using a ZnSe single crystal, and (b) using different types of crystals having the same lattice constant. In the former case, a Zn5e single crystal grown by the Bridgman method or Czochralski method is used, but the Zn5e single crystal grown by these methods has an extremely large number of crystal defects called dislocations, so epitaxial growth is performed on top of the Zn5e single crystal. In order for these crystal defects to propagate to the Zn5e thin film, high-quality Zn5e
A thin film cannot be obtained, and the characteristics as a light emitting element are therefore deteriorated. Regarding the latter, G of the ■-■ group compound semiconductor
The lattice constant of aAs is 5.653, which is close to the lattice constant of Zn5e, 5.6676 to 5.6687, so GaAs
Research is being conducted on its use as an f-substrate. However, even in this combination of Zn5e/GaAs, the difference in lattice constant is as much as 3%, and this rounding causes crystal defect dislocations to occur in the ZnS e epitaxial film (see Figure 2). Figure 2 shows an example of a conventional element. 1 in the figure.
is a GaAs substrate, 2 is a Zn5e thin film, 3 is a dislocation in the GaAs substrate, 4 is a dislocation propagated into Zn5e, and 5 is a Zn5
This shows a friend defect caused by lattice mismatch between e and GaAs.

For this purpose, a film of a ternary mixed crystal Zn5e□-S film of Zn5e and ZnS may be formed in order to match the lattice constant of the GaAs substrate, but it is difficult to control the composition and it is difficult to obtain a high-quality film. In addition, crystal defects (
Z
n5e epitaxial propagation to the olfactory. Under these conditions, it is still impossible to obtain a Zn5e film of good quality, and it is difficult to obtain high characteristics as a blue light emitting element.

(Friendly Means for Solving Problems) The present invention provides a crystal substrate having the same lattice constant as Zn5e and free from crystal defects, which is essential for forming a high-quality Zn5e epitaxial film. The purpose of this invention is to realize a blue light emitting device with high characteristics.

The present invention uses In as a crystal substrate that completely matches the lattice constant of Zn5e epitaxial layer and has no crystal defects.
i-added or alloyed fc GaAs i.e. In-G
The most important feature is that the substrate is an a1-air As ternary mixed crystal.

The structure of the light emitting device is completely different from that of the conventional device, which uses an hGaAs binary crystal as a substrate.

FIG. 1 shows the most basic embodiment of the present invention. In the figure, 6 is an In□Ga knee□As ternary mixed crystal substrate, and 7 is a Zn5e thin film single crystal.

As mentioned above, the lattice constant of Zn5e is 5.66 at room temperature.
76-5.6687 A f 6 Ru. On the other hand, GaAs of the m-v group compound semiconductor has the same < 5.653 A, and InAs has 6.058 A.
Since InAs is a so-called totally dissolved form that can be single crystallized at any ratio, the lattice constant can take a value between 5.653 A and 6.058^ depending on the ratio of Ga and In. Therefore, the well-known Vega
rds), the In/Ga ratio is set to 0.03410.
．． By setting it to 966~0.038/0.962”
0. Q3! G'0.966 ” ~ Engineering n0.038Ga
The lattice constant of O,962A8 ternary mixed crystal is 5.6676~5
．． That's 6,687 people.

Such a ternary mixed single crystal can be grown by adding In to a GaAs melt to a concentration of about 8.6 x 10"crn-" and by a pulling method (Czochralski method) or the like.

However, since the In concentration in the crystal gradually increases along the longitudinal direction (growth direction) of the crystal, if at least I x 10"CM-' is added to the GaAs melt and the crystal is pulled and grown, the In concentration in the crystal body increases. is 8.6 x 10”+10
tscm' crystals are obtained. The crystal obtained in this way has a solid solution hardening effect due to the addition of In (which can also be referred to as an alloy ratio since it is a total solid solution), which has the effect of extremely suppressing the generation of dislocations in the crystal. . In fact, In, Ga1-, AB (Z = 0
．． It was confirmed that there were almost no dislocations, which are crystal defects, in the crystal of 01-0.04).

This “0.034GaO, 965AS and ■no, o4
Using a Gao+96A8 crystal as a substrate, we epitaxially grow a thin Zn5e single crystal using the vapor phase growth method.As a result, the lattice is well matched and there are no dislocations in the substrate, resulting in a high-quality thin film with extremely few crystal defects. This was confirmed by X-ray analysis. This structure allows Zn5
A good light-emitting device can be obtained by completely forming a p-n junction instead of an e-epitaxial layer.
, indicates the lattice constant of a ternary material such as InGaAs.

Table 1 Note that in this example, In concentration sc = 0.034
I mentioned Zn5e? Since the lattice constant changes slightly depending on the growth method of the I film, it is clear that the value of 5 can be divided between 0.03 and 0.045. A dislocation-free ternary substrate is good.

Ma2. An In-Ga-Air-As mixed crystal single crystal of GaAs added or alloyed with In can be grown by the well-known horizontal Bridgman method, but in the present invention, it is not limited by the manufacturing method of this mixed crystal. It's not something you can do.

(Effects of the invention) As explained above, by adding In of the present invention, nine GaAs
According to the crystal, (a) it has the characteristics of lattice matching with ZnSe and (c) there are no dislocations, which are crystal defects, so it has the advantage of being able to grow high-quality Zn5e epitaxial single crystal thin films, and has high properties. This has the effect that a color light emitting element can achieve.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an embodiment that clearly shows the feature of the present invention, including the amount of metal, and FIG. 2 shows a device structure that has been considered in the past. 1...GaAs substrate 2...Zn5e thin film 3...Dislocations in GaAs substrate 4...
Propagates into Zn5e and dislocation 5...Zn5e (
! : In, Ga1-xAs mixed crystal substrate (g=0.03
8±IO%] 7...Zn5e thin fusuma patent applicant Nippon Telegraph and Telephone Corporation Figure 1 Figure 2

Claims (2)

[Claims] (1) In a particularly blue light-emitting device in which a thin film of a II-VI compound semiconductor consisting of an element belonging to Group II and an element belonging to Group VI in the periodic table is epitaxially grown on a crystal substrate,
III-V in which In is added or alloyed to the crystal substrate
A light-emitting device characterized by using GaAs, a group compound semiconductor crystal. (2) The composition x of the In_xGa_1_-_xAs mixed crystal is 0
．． The light emitting device according to claim 1, characterized in that a substrate having a molecular weight of 0.030 to 0.045 is used.