JPH01268174A - Manufacture of light emitting element - Google Patents

Abstract

PURPOSE:To manufacture a high intensity light emitting diode with a GaAlAs light transmission layer having high yield and mass productivity by forming a protective film on one side surface of a Ga1-xAlxAs substrate, and then epitaxially growing a GaAlAs layer to become a light emitting layer on the other side surface of the substrate. CONSTITUTION:After both the surfaces of a Ge-doped p-type Ga0.55Al0.45As substrate 1 is polished in a mirror-surface, they are etched, and an SiO2 film 8 is formed as a protective film on one side surface. Thereafter, the other side surface is etched with an etchant, and it is contained in a liquid epitaxially growing slide boat with the other side surface disposed above. The whole boat is heated, unsaturated solution of Ga, GaAs, Al is first brought into contact with the surface of the substrate, and a Zn-doped P-type Ga0.3Al0.7As layer 2. an undoped Ga0.65Al0.35As layer 3, a Te-doped N-type Ga0.3Al0.7As layer 4, a Te-doped N-type Ga0.55Al0.45As layer 5 are sequentially grown. Then, the film 8 covering the rear surface of the substrate 1 is removed by dissolving. Then, a P-type electrode 6 is formed on the rear surface of the substrate 1, an N-type electrode 7 is formed on the layer 5 side, and it is then pelletized.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a light emitting device, and in particular, a high power GaM device having a GaAl5 light transmitting layer for effectively extracting light.
The present invention relates to a method for manufacturing an AS-based light emitting diode.

[Prior Art] The market for GaAlAs light emitting diodes is expanding due to their excellent high output and high speed response. Recently, higher output has been desired, and as a result, a light-emitting diode having a structure in which a light-transmitting layer is a Ga1-xM x A triple layer that absorbs emitted light has been developed. Here, in order to function as a light-transmitting layer, the AQ mixed crystal ratio X defines the emission wavelength.
It is necessary that the hemi-2 mixed crystal ratio y is greater than <1).

Now, as one of the actual manufacturing methods of the above-mentioned light emitting diode, G
There is a method of using the a1-χΔ2χAs layer as a substrate for epitaxially growing the light emitting part. Here, G
Above a+-xAlxAsA2, this Ga, -χAQ
Ga used when epitaxially growing xA S
It is preferable that the As substrate be removed because internal stress due to the difference in lattice constant between GaAS and the GaAs substrate, which causes curvature and cracking of the epitaxial wafer, can be reduced. Ga1−χAQχ with the GaAs substrate removed in this way
If the 8s group is used, an electrode can be formed on the back side of the Ga1-χAQ XA S substrate immediately after epitaxial growth of the light emitting part.

Therefore, in the prior art, a thickness of 100 μm that is transparent to the emission wavelength is formed by epitaxial growth on a GaAs substrate.
Grow a χAs layer to Ga1−χ of m or more, and then
The GaAs substrate is completely removed by etching or polishing, and the
A wafer consisting of an a+-χ gate χAs layer was prepared, and the surface of this wafer was subjected to etching or the like prior to epitaxial growth to serve as a substrate for epitaxial growth of a light-emitting layer.

As mentioned above, in the prior art, Ga1-χAQ
Since the χAs substrate is subjected to surface treatment such as etching and then placed in an epitaxial growth apparatus to grow the light-emitting layer, there are various treatments on the surface opposite to the surface (back surface) of the Ga1-χAs substrate where the epitaxial growth is performed. Defects occur.

Epitaxial growth is usually performed in a non-oxidizing atmosphere at 700 ~
For example, in the case of liquid phase epitaxial growth, a trace amount of oxygen contained in the Graphi h boat and the raw material Ga diffuses into the atmosphere as the temperature rises. The back surface of χAQχAs is oxidized. Even in epitaxial growth using the MO-CVD method, oxidation of Ga1-χAρχAs occurs similarly due to oxygen adsorbed in the susceptor and reaction tube.
Clouding occurs on the back surface of Ga+-χARχAs. Also, when ΩχAs is heated to 700°C or higher to Ga, -χ,
As is a volatile component, it becomes easy to evaporate, and as a result, the back surface of the substrate loses its luster and countless minute irregularities occur. The above-mentioned oxidation reaction appears more prominently as the λ mixed crystal ratio of Ga+-xAlxAs increases; for example, when x=0.45
In this case, liquid phase epitaxial growth is performed from 900°C to 7°C.
When carried out at 00℃ for about 3 hours, Ga+-χMχ
To 8s^S The back side of the board becomes rough and loses its luster.

In this way, if the back surface of the Ga, -χAQχAs substrate is rough and rough, if a light emitting diode is manufactured as is, the light emitted from the light emitting part will be Ga1 -χ^2χ8S
The light is diffusely reflected by minute irregularities on the surface of the overlayer, that is, the back surface of the Ga1-xAlxAs substrate, resulting in light loss, which significantly impairs luminous efficiency. For this reason, conventionally, after epitaxial growth, the back surface of the S layer is mirror-finished by polishing or etching to the Ga1-.chi.-poor .chi. However, here the following drawbacks and inconveniences appear.

The wafer after epitaxial growth is Ga+-χA
QxA S substrate, Ga + -v AQ NA S layer, light emitting layer, Ga
Traditionally, the wafer is distorted due to stress inside the wafer due to the difference in the mixed crystal ratios X, V, and Z, and the wafer is curved. When processing such a wafer into a mirror surface by polishing, for example, it is very difficult to obtain thickness accuracy, and secondly, the wafer often cracks due to the above distortion, resulting in diode damage. This causes a decrease in yield. The above two are the main drawbacks, and in addition, it is extremely difficult to obtain a thick Ga1-χAQχAs substrate itself, and a thin substrate of usually less than 200 μm must be used, so the wafer is very easy to break. This makes it difficult to eliminate deficiencies.

“Problems to be Solved by the Invention” As mentioned above, several hundred μm of GaAs are deposited on a GaAs substrate.
By epitaxially growing a superlayer on Q8S light, the original Ga
In a manufacturing method that removes the As substrate and then epitaxially grows a light-emitting portion of a GaAlAs light-transmissive layer on the light-transparent upper layer lever to efficiently extract light, epitaxial growth of about 40 μm is usually performed to obtain the light-emitting portion. It is common for the surface of an epitaxial layer to have irregularities due to morphology or protruding growth portions.

This lick is applied to the = 6- back side of the wafer after epitaxial growth, i.e., GaAJ! It is necessary to polish the back surface of the As substrate in order to increase the reflection efficiency, but there are the following disadvantages when polishing.

(1) It is necessary to attach the epitaxial layer surface to a flat plate, but due to the unevenness of the epitaxial layer surface, it is difficult to attach it flatly, and it is difficult to maintain the accuracy of the thickness after polishing. Can not.

(2) Since it is necessary to use a GaAl5 substrate which is inherently susceptible to cracking during manufacturing, the above-mentioned distortion causes cracks in the wafer and reduces the yield of diodes.

As a result, it has hitherto been difficult to obtain a high-brightness light emitting diode with a GaAl5 light-transmitting layer that can be easily mass-produced.

The object of the present invention is to solve the above-mentioned drawbacks of the prior art, and to provide a GaJV! with high yield and high mass productivity! An object of the present invention is to provide a method for manufacturing a light emitting element that can manufacture a high brightness light emitting diode with an As light transmitting layer.

[Means for Solving the Problems] The method for manufacturing a light emitting device of the present invention provides a method for manufacturing a light emitting device, in which on a Ga+-XM S substrate formed as a light transmitting layer transparent to the emission wavelength,
A GaAlAs layer that becomes a light emitting layer is epitaxially grown, and the light emitted from this GaAlAs layer is the Ga)-x
After passing through the AQxAs substrate, it is reflected on the surface and GaA
In the method for manufacturing a light-emitting device taken out from the lAs layer side, after forming a protective film on one surface of the Ga1-xAlxAs substrate, a GaA layer that will become the light-emitting layer is formed on the other surface of the Ga1-xAlxAs substrate.
The lAs layer is epitaxially grown.

In the present manufacturing method, it is desirable to finish one surface of the Ga+-χAQ xA S substrate to a mirror finish, form a protective film on that surface, and epitaxially grow a GaAlAs layer that will become a light emitting layer on the other surface.

Further, in this manufacturing method, after epitaxially growing the GaAlAs layer that will become the light emitting layer, part or all of the protective film can be removed.

The mixed crystal ratio of the Gal-χ^-containing χAs substrate that becomes the light-transmitting layer is 0.
<×<1.

In addition, the type of protective film should be one that can prevent thermal and chemical damage to the back side of the Ga+-χAQ xA S substrate at the intended epitaxial growth temperature. It can be arbitrarily selected taking into account that the xAS is not damaged, that the protective film is easy to form and remove, and that the characteristics of the light emitting diode are not impaired. The most suitable film for the above purpose is 5102 film formed by chemical vapor phase reaction, but SiN, 5i
It is possible to freely select ON, ^QN, etc.

In addition, for the purpose of improving the reflection effect on the back surface of the Ga1-χAQ xA S substrate, that is, the surface of the light transmission layer,
Even if a film is formed, if it has the effect of substantially preventing roughening of the back surface of the substrate, such a film is also included in the protective film of the present invention.

As long as the light emitting diode is manufactured using a Ga+-χ^λχAs substrate, the present invention can be applied regardless of the type, structure, and manufacturing process of the diode.

If a protective film is formed on one surface of the Ga1-χAQχAs substrate, when epitaxial growth is performed on the other surface, this protective film protects one surface of the substrate from thermal
Protected from chemical stress. Therefore, there is no need to polish the wafer after epitaxial growth.
If the thickness of the Ga+-xAlxAs substrate is adjusted with good precision before epitaxial growth, an epitaxial wafer with good thickness precision can be obtained, and subsequent processes can be carried out smoothly.

Then, if one surface of the As substrate is finished with a mirror finish on the Ga + - Light is efficiently reflected from the surface of the transparent layer and can be effectively extracted from the light emitting layer side.

Furthermore, if the protective film is not formed for the purpose of improving the reflection effect, but merely for the purpose of protecting one surface of the substrate, this layer may be removed after epitaxial growth. The protective film may be removed if necessary.

-10- [Example] Examples of the present invention will be described below with reference to FIGS. 1 and 2.

Diameter 40 m1'Il, thickness 150 μrn, crystal plane (
100) Ge-doped, p-type, Gao, 55AQ 0
．． After polishing both sides of the 45^S substrate 1 to a mirror surface, it was etched with an etching solution consisting of sulfuric acid (4 volumes), hydrogen peroxide (1 volume), and water (1 volume), and SiH4 scum and Due to the gas phase reaction of 02 dregs, the thickness of 51
02 film 8 was formed as a protective film. Thereafter, the other side was etched with the etching solution mentioned above, and the substrate was placed in a slide boat for liquid phase epitaxial growth with this side facing up.

The whole boat is heated to 900℃, and first Ga, GaAs,
An unsaturated solution consisting of AQ was brought into contact with the substrate surface, and after the substrate surface was melted back by about 10 μm, the temperature was lowered at a cooling rate of 1° C./min.
o7As layer 2 15 μm thick, undoped Gao6sA
Qo3s^S layer 3 is 1 μm thick, Te-doped n-type Gao,
3Mo7As layer 4 of 20 μm thickness, Te doped n-type G
ao, 55AQ. 4. The As layer 5 was grown to a thickness of 1 μm (
Figure 1).

The time required during this time was approximately 2.5 hours. Thereafter, the wafer was taken out at room temperature and immersed in a hydrofluoric acid aqueous solution for 1 minute. AQ. 5i02@8 deposited on the back surface of the 45AS substrate 1 was dissolved and removed. In this state Gao
, 5sAQ o, <5^S The back surface of the substrate 1 was completely mirror-like with no oxidation or As scattering. Next, Gao, 5s Aflo, 498S pI! on the back side of substrate 1. ! After forming the n-side electrode 7 on the Te-doped n-type epitaxial layer 5 side by vapor deposition and photolithography, assemble it into a predetermined stem (see Figure 2) and apply a current to I'-20111. When the emission wave and brightness were measured, the emission center wavelength was 660n.
n, the brightness was 2 (1 mcd).The brightness of a light emitting diode with the same light emitting layer structure without a light transmitting layer was about 10 mcd, and the light emitted from the light emitting part was Gao5.AQ 0.4
The surface of the 5AS light transmitting layer, namely Gao, 5sAQ. 4.
It can be seen that the light is reflected efficiently from the back surface of the As substrate.

Since there was no need to polish or etch the back surface of the 2.chi.As to Ga+-.chi. after epitaxial growth, there was no loss due to cracking of the wafer, and the yield of the diode was as high as 95%.

According to the above embodiment, Ga1- after epitaxial growth
Since the back surface of the χAQχN substrate does not lose its gloss and has a perfect mirror surface, there is no need to perform mirror polishing after epitaxial growth as in the conventional method, and no cracking of the wafer occurs. This makes it possible to increase the size of the wafer, and while the conventional wafer area was limited to 2CI112, it can be expanded to approximately 12cm2 (diameter 401111'N), greatly improving mass productivity. I can do it.

[Effect of the invention] According to the present invention, there are the following effects.

After forming a protective film on one surface of the Ga+-χ^2χAs substrate, a five-layer GaAl layer that will become a light-emitting layer is epitaxially grown on the other surface, so thermal and chemical damage to the surface of the Ga1-χAQχAs substrate can be prevented. Therefore, it is not necessary to remove the damaged portion on one surface of the substrate after epitaxial growth, and therefore a high-brightness light emitting diode can be manufactured with high yield and high mass productivity.

When one surface of the substrate is polished to a mirror surface, a protective film is formed on that surface, and a GaAl5 layer is epitaxially grown on the other surface, the gloss of one surface of the substrate after epitaxial growth is not lost and the surface is completely mirror-finished. can be maintained, so the reflection efficiency can be significantly increased.

If part or all of the protective film is removed after epitaxially growing the five-layer GaAl layer, an undamaged substrate surface appears, and electrodes can be immediately formed on this substrate surface.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an epitaxial wafer after forming a light emitting layer, showing one embodiment of the method for manufacturing a light emitting device of the present invention;
FIG. 2 is a sectional view showing a GaAlAs light emitting diode with a GaAlAs light transmitting layer. In the figure, 1 is P-type Ga1-χAQχAs as a light-transmitting layer.
Substrates 2 to 5 are GaAl5 layers serving as light emitting layers;
is a p-type GaAl5 epitaxial layer, 3 is an undoped GaAlAs epitaxial layer, and 4 and 5 are n-type GaAl
As epitaxial layer, 8 is 5iO2J as a protective film
It is Iu.

Claims (1)

[Claims] 1. Ga_1 formed as a light-transmitting layer transparent to the emission wavelength
GaAl serving as a light emitting layer is placed on the ____xAl_xAs substrate.
In the method for manufacturing a light emitting device, in which an As layer is epitaxially grown, light emitted from the GaAlAs layer passes through the Ga_1_-_xAl_xAs substrate, is reflected on the surface thereof, and is extracted from the GaAlAs layer side.
_1_-_xAl_xAfter forming a protective film on one surface of the As substrate, GaAlA, which will become the light emitting layer, is formed on the other surface.
A method for manufacturing a light emitting device, comprising epitaxially growing an s-layer. 2. The manufacturing method according to claim 1, characterized in that one surface of the Ga_1_-_xAl_xAs substrate is finished to a mirror finish, a protective film is formed on that surface, and a GaAlAs layer serving as a light emitting layer is epitaxially grown on the other surface. . 3. The manufacturing method according to claim 1 or 2, wherein part or all of the protective film is removed after the GaAlAs layer serving as the light emitting layer is epitaxially grown.