JP2000058904A - Epitaxial wafer and its manufacture as well as light emitting diode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an epitaxial wafer in which a p-type inversion is not generated in a part near the bonding part of a substrate to an n-type clad layer, in which a light fetching face is a p-type layer and whose yield is high and to provide its manufacturing method as well as to provide a light emitting diode. SOLUTION: An n-type GaAlAs clad layer 2, a p-type GaAlAs active layer 3 and a p-type GaAlAs clad layer 4 are formed sequentially on an n-type GaAs substrate 1 by a liquid-phase epitaxial method. At this time, the concentration of C in the n-type GaAlAs clad layer 2 is set at 1.0×1018 cm-3 or lower, and an epitaxial wafer is manufactured sequentially. As a result, the peak concentration of C becomes lower than the concentration of Te near the bonding part of the n-type GaAlAs clad layer 2 to the n-type GaAs substrate 1, and a p-type inversion is not generated near the bonding part. When the epitaxial wafer is used, it is possible to obtain a light emitting diode in which a light fetching face is the p-type GaAlAs layer 3 and whose yield is high.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an epitaxial wafer, a method for manufacturing the same, and a light emitting diode.

[0002]

2. Description of the Related Art The structure of an epitaxial wafer for a GaAlAs-based red light emitting diode (LED) manufactured by a liquid phase epitaxial method is mainly of a type in which a light extraction surface is an n-type layer.

FIG. 2 is a sectional view of a conventional epitaxial wafer.

[0004] This epitaxial wafer is made of p-type GaAs.
A p-type GaAlAs cladding layer 6, a p-type GaAlAs active layer 7, and an n-type GaAlAs cladding layer 8 are sequentially formed on an s substrate 5.

When this type of epitaxial wafer is used for a multicolor light-emitting display, the light extraction surface of the LED other than red is a p-type layer and has a different conductivity type, so that the light extraction surface is a p-type layer. There is also a lot of demand.

[0006]

However, a type in which the light extraction surface is a p-type layer (on an n-type GaAs substrate,
An n-type GaAlAs cladding layer, a p-type GaAlAs active layer, and a p-type GaAlAs cladding layer sequentially formed)
Is difficult to control the junction of the n-type GaAs substrate and the n-type GaAlAs cladding layer with n-type, so that the production yield is low. Further, Zn used as a p-type dopant has a property of being very easily diffused at a temperature (700 to 900 ° C.) at which epitaxial growth is performed.

For this reason, Zn in the solution of the p-type active layer and the p-type cladding layer diffuses into the n-type substrate and the n-type cladding layer, which makes it difficult to control the n-type.

As countermeasures, increasing the amount of dopant Te in the n-type cladding layer and decreasing the amount of Zn in the p-type active layer and the p-type cladding layer have been studied but are insufficient.

Therefore, an object of the present invention is to solve the above-mentioned problems, there is no p-type inversion near the junction between the substrate and the n-type cladding layer, the light extraction surface is a p-type layer, and the yield is high. An object of the present invention is to provide an epitaxial wafer, a method for manufacturing the same, and a light emitting diode.

[0010]

In order to achieve the above object, a method of manufacturing an epitaxial wafer according to the present invention comprises the steps of:
An epitaxial wafer having a double hetero structure in which an n-type GaAlAs cladding layer, a p-type GaAlAs active layer having an Al mixed crystal ratio required for a desired emission wavelength, and a p-type GaAlAs cladding layer are sequentially formed on an aAs substrate by a liquid phase epitaxial method. In the manufacturing method, each layer is sequentially formed with the C concentration in the n-type GaAlAs cladding layer being 1.0 × 10 ¹⁸ cm ⁻³ or less.

The epitaxial wafer of the present invention has an n-type G
An epitaxial wafer having a double hetero structure in which an n-type GaAlAs cladding layer, a p-type GaAlAs active layer having an Al composition ratio required for a desired emission wavelength, and a p-type GaAlAs cladding layer are sequentially formed on a aAs substrate by a liquid phase epitaxial method. In the n-type GaAlAs cladding layer
The concentration is 1.0 × 10 ¹⁸ cm ⁻³ or less.

The light emitting diode of the present invention is an n-type GaAs
On a substrate, an n-type GaAlAs cladding layer, a p-type GaAlAs active layer having an Al mixed crystal ratio required for a desired emission wavelength,
In a light emitting diode in which an anode electrode and a cathode electrode are provided on an epitaxial wafer having a double hetero structure in which a GaAlAs cladding layer is sequentially formed by a liquid phase epitaxial method, the C concentration in the n-type GaAlAs cladding layer is set to 1.0 × 10 ¹⁸ cm ^{− 3} or less.

According to the present invention, the C concentration in the n-type GaAlAs cladding layer is controlled to be 1.0 × 10 ¹⁸ cm ⁻³ or less, and the epitaxial wafer is sequentially formed, whereby the peak C
Since the concentration is lower than the Te concentration near the junction between the n-type cladding layer and the substrate, p-type inversion does not occur near the junction. By using such an epitaxial wafer, a light-emitting diode having a light extraction surface of a p-type layer and a high yield can be obtained.

[0014]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

The present inventors have proposed an n-type GaAs substrate and an n-type G
It has been found that the cause of the formation of the p-type inversion layer at the junction with the aAlAs cladding layer is not only Zn diffusion but also the impurity C (carbon) contained in the n-type cladding layer.

FIG. 3 shows an n-type GaAs substrate and an n-type GaAlA.
C concentration SIMS near the junction with the s cladding layer (Second
FIG. 4 is a diagram showing measurement results of ary ion mass spectroscopy (secondary ion mass spectroscopy). In the figure, the horizontal axis indicates the depth,
The vertical axis indicates the concentration.

Since the growth jig used for liquid phase epitaxial growth is made of graphite, C is naturally contained in the solution. Therefore, C is also contained in the epitaxial layer, but its peak concentration is 2 × 10 ¹⁸ cm ^−3.
The above high concentration.

Usually, the Te concentration near the substrate junction of the n-type cladding layer is 0.5 to 1.0 × 10 ¹⁸ cm ⁻³ ,
If C, which is a p-type impurity, is further contained, the n-type cladding layer is inverted to the p-type cladding layer.

Therefore, the impurity C in the n-type cladding layer
The concentration must be lower than the Te concentration of the n-type cladding layer. That is, the Te concentration near the junction between the n-type cladding layer and the substrate must be 0.5 to 1.0 × 10 ¹⁸ cm ⁻³ or less.

When the Te concentration near the junction between the n-type cladding layer and the substrate is set to 1 × 10 ¹⁸ cm ⁻³ or more, the light emission output is extremely reduced.

[0021]

FIG. 1 is a sectional view of an epitaxial wafer to which the method of manufacturing an epitaxial wafer according to the present invention is applied.

Such an epitaxial wafer was manufactured as follows.

The epitaxial growth jig (not shown)
A graphite jig with a PBN coating was used. An n-type GaAs substrate 1 and Ga, GaAs, Al, Zn, and Te, which are raw materials for an epitaxial layer, were set in an epitaxial growth jig and set in a liquid phase epitaxial growth apparatus.

The n-type GaAs substrate 1 was heated together with the epitaxial growth jig to about 900 ° C. and maintained for 3 hours in a hydrogen stream, and then cooled to about 700 ° C. at a rate of 1 ° C./min. During cooling, the n-type GaAs substrate 1 is sequentially brought into contact with the growth solution, and the n-type GaAlAs cladding layer 2 and the p-type GaAlA
The s active layer 3 and the p-type GaAlAs cladding layer 4 were sequentially grown by liquid phase epitaxial growth. The Te concentration near the junction between the n-type GaAlAs cladding layer and the substrate was 1 × 10
^The growth was performed under conditions so as to be ¹⁸ cm ^-3 .

Using the half surface of the obtained epitaxial wafer, a C concentration SIMS measurement near the substrate interface was performed. An anode electrode and a cathode electrode were formed on the remaining half surface of the epitaxial wafer, and divided into chips by dicing. The divided chip was mounted on a stem and coated with an epoxy resin to form a light emitting diode.

As a comparative example, an epitaxial wafer was prepared under the same conditions as described above using a commonly used graphite jig without PBN coating, and a C concentration SIMS measurement was similarly performed using a half surface. And a light emitting diode was fabricated on the other half.

Table 1 is a table showing the current-voltage characteristic defect occurrence rate and the peak C concentration of the n-type cladding layer in this embodiment and the comparative example.

[0028]

[Table 1]

From the table, it can be seen that when a light emitting diode is manufactured using the epitaxial wafer of this embodiment, the defect occurrence rate is as low as 1/30 as compared with a light emitting diode using a conventional epitaxial wafer. This is because the peak C concentration has a T value near the junction between the n-type cladding layer and the substrate.
This is because p-type inversion does not occur near the junction because the concentration is lower than the e concentration.

Although the present embodiment has been described with reference to the epitaxial wafer having the double hetero structure, the present invention can be applied to a back reflection type light emitting diode formed by removing the GaAs substrate from the epitaxial wafer having the double hetero structure.

[0031]

In summary, according to the present invention, the following excellent effects are exhibited.

By setting the C concentration in the n-type GaAlAs cladding layer to 1.0 × 10 ¹⁸ cm ⁻³ or less, there is no p-type inversion near the junction between the substrate and the n-type cladding layer.
An epitaxial wafer having a light extraction surface of a p-type layer and having a high yield, a method for manufacturing the same, and provision of a light emitting diode can be realized.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an epitaxial wafer to which an epitaxial wafer manufacturing method according to the present invention is applied.

FIG. 2 is a sectional view of a conventional epitaxial wafer.

FIG. 3 is a diagram showing a C concentration SIMS measurement result near a junction between an n-type GaAs substrate and an n-type GaAlAs cladding layer.

[Description of Signs] 1 n-type GaAs substrate 2 n-type GaAlAs cladding layer 3 p-type GaAlAs active layer 4 p-type GaAlAs cladding layer

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5F041 AA41 CA04 CA12 CA35 CA36 CA49 CA53 CA57 CA63 CA67 CA76 CB15 DA19 DA44 FF01 FF06

Claims (3)

[Claims] An n-type GaAs substrate is provided on an n-type GaAs substrate.
In the method for manufacturing an epitaxial wafer having a double hetero structure in which an s cladding layer, a p-type GaAlAs active layer having an Al mixed crystal ratio required for a desired emission wavelength, and a p-type GaAlAs cladding layer are sequentially formed by a liquid phase epitaxial method, When the C concentration in the GaAlAs cladding layer is 1.0 × 1
A method for manufacturing an epitaxial wafer in which each of the above layers is sequentially formed at a temperature of 0 ¹⁸ cm ⁻³ or less. 2. An n-type GaAs substrate on which an n-type GaAlA
In an epitaxial wafer having a double hetero structure in which an s cladding layer, a p-type GaAlAs active layer having an Al mixed crystal ratio required for a desired emission wavelength, and a p-type GaAlAs cladding layer are sequentially formed by a liquid phase epitaxial method,
The C concentration in the AlAs cladding layer is set to 1.0 × 10 ¹⁸ cm ⁻³
An epitaxial wafer characterized by the following. 3. An n-type GaAs substrate on which an n-type GaAlA
An anode electrode and a cathode electrode are provided on an epitaxial wafer having a double hetero structure in which an s cladding layer, a p-type GaAlAs active layer having an Al composition ratio required for a desired emission wavelength, and a p-type GaAlAs cladding layer are sequentially formed by a liquid phase epitaxial method. In the light emitting diode, the n-type G
a The concentration of C in the AlAs cladding layer is set to 1.0 × 10 ¹⁸ cm
A light emitting diode characterized by having a value of ^-3 or less.