JP2001156007A - AlGaAs EPITIAXIAL WAFER FOR LIGHT-EMITTING DIODE AND METHOD OF MANUFACTURING THE SAME - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new AlGaAs epitaxial wafer for light-emitting diode, in which thyristor phenomenon areas hardly occur, and to provide a method of manufacturing the wafer. SOLUTION: In the AlGaAs epitaxial wafer for light-emitting diode, which is constituted by successively forming a p-type AlGaAs layer 2 and an n-type AlGaAs layer 3 on a GaAs single-crystal substrate 1, carbon (C) concentration in the n-type AlGaAs layer 3 is adjusted to be 1.0×1017/cm3 or lower, so as to suppress the occurrence of thyristor phenomenon areas in the wafer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an AlGaAs for a light emitting diode (LED) used as a material for a light emitting diode (LED).
The present invention relates to an epitaxial wafer and a method for manufacturing the same.

[0002]

2. Description of the Related Art In general, an epitaxial wafer for an infrared or visible light emitting diode (LED) is formed on a GaAs substrate surface by n
It is manufactured by forming a GaAs layer or an AlGaAs layer adjusted to the p-type and the p-type on a single hetero (SH) or double hetero (DH) structure by a liquid phase epitaxial growth method (LPE method).

However, in such a conventional epitaxial wafer for a light emitting diode, an n-type AlG
In some cases, a p-type inverted layer may be formed in a part of the aAs layer near the pn junction, and a region showing a thyristor phenomenon may be generated. In some cases, it may cause defective products not having the above.

For this reason, it is preferable to detect only the region exhibiting the thyristor phenomenon in advance and manufacture the product using the remaining sound portion. However, the thyristor phenomenon is caused in a few percent of the area within the epitaxial wafer surface. Since it occurs at random, it has been difficult to detect in a wafer state.

The present invention has been devised to solve such a problem, and an object of the present invention is to provide a novel AlGaAs epitaxial wafer for a light emitting diode in which generation of a thyristor phenomenon region is suppressed and a method of manufacturing the same. Is provided.

[0006]

The p-type inversion layer causing the thyristor phenomenon as described above is formed by diffusing a part of zinc (Zn) conventionally used as a p-type dopant into an n-type layer. Was thought to only occur.

However, as a result of examining the composition of the location where the thyristor phenomenon occurred using the latest analytical instruments and techniques, the location where the thyristor phenomenon occurred (the p-type inversion layer) was found to be smaller than that of the normal region. (C)
It was confirmed that the concentration was high.

More specifically, as shown in FIG. 2, a partial carbon concentration peak exists in the thickness direction of the n-type AlGaAs layer in the place where the thyristor phenomenon occurs, whereas in the normal part, this peak is present. There is no peak, and the carbon concentration distribution is relatively flat.

Therefore, as a means of suppressing the thyristor phenomenon, it is conceivable to eliminate the occurrence of the carbon peak. However, the carbon concentration peak is completely eliminated because it is caused by a subtle change in the environmental growth environment in the LEP method. It is difficult.

On the other hand, as shown in the drawing, the carbon concentration is about 3 × 10
^Since it can be seen that p-type inversion occurs when it exceeds ¹⁷ / cm ³ , it is considered that the thyristor phenomenon can be prevented by controlling the overall carbon concentration to be low so that the peak concentration does not exceed this value. Can be Further, the peak concentration is about twice as high as that of the other parts (flat distribution part), and in order to make the peak concentration not more than about 3 × 10 ¹⁷ / cm ³ , the concentration of the flat distribution part is at least. 1.5 × 10
It can be said that it is necessary to be less than ¹⁷ / cm ³ , but in order to surely prevent the occurrence of the thyristor phenomenon, it is considered to be more preferably less than 1.0 × 10 ¹⁷ / cm ³ with a margin.

Therefore, the present invention provides an AlGaAs epitaxial wafer for a light-emitting diode in which a p-type AlGaAs layer and an n-type AlGaAs layer are formed on a GaAs single crystal substrate by a liquid phase epitaxial method, as described in the claims. The concentration of carbon (C) in the n-type AlGaAs layer is less than 1.0 × 10 ¹⁷ / cm ³ .

Then, such an Al for a light emitting diode is used.
As a method for manufacturing a GaAs epitaxial wafer, as described in claim 2, when forming the n-type AlGaAs layer, a carbon epitaxial growth jig is coated in advance, and then the n-type AlGaAs epitaxial layer is grown. It was done.

That is, as a material of the jig for epitaxial growth by the LPE method, a jig for epitaxial growth made of carbon such as a graphite slide board is used, and this mixes carbon into the epitaxial layer, particularly the n-type AlGaAs layer. It is considered to be the source.

[0014] Therefore, by coating the jig for epitaxial growth in advance with a P-BN thin film or the like, the incorporation of carbon from the jig for epitaxial growth into the n-type AlGaAs layer is suppressed.
The carbon (C) concentration in the s layer is 1.0 × 10 ¹⁷ / cm ³
An AlGaAs epitaxial wafer for a light emitting diode of less than 3 can be reliably obtained.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a preferred embodiment of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows an embodiment of an epitaxial wafer having a single hetero structure among the epitaxial wafers for light emitting devices (hereinafter, referred to as an epitaxial wafer) according to the present invention.

As shown in the figure, an AlGaAs layer 2 adjusted to p-type is formed on a GaAs single crystal substrate surface 1 by LPE.
Formed by the epitaxial growth method.
On the p-type AlGaAs layer 2, A
The lGaAs layer 3 also has a laminated structure formed by the epitaxial growth by the LPE method.

The carbon (C) concentration in the n-type AlGaAs layer 3 is 1.0 in the flat concentration distribution portion.
Less than × 10 ¹⁷ / cm ³ , 2.0
It is designed to be suppressed to less than × 10 ¹⁷ / cm ³ .

Therefore, as described above, n-type AlGaAs
In the s layer 3, there is almost no generation region of the p-type inversion layer due to the carbon mixing, so that there is almost no region where the thyristor phenomenon occurs. As a result, a high-quality light emitting diode without the thyristor phenomenon ( LED chip)
Can be reliably provided.

In order to obtain such an epitaxial wafer, when the n-type AlGaAs layer 3 is epitaxially grown, a surface of a carbon epitaxial growth jig serving as a carbon contamination source is coated in advance. Can be achieved. Specifically, when the most common slide board method is used as the LPE method, a graphite carbon slide board is used as a jig for carbon epitaxial growth. By coating the vicinity of the mounting portion of the AlGaAs layer growth solution with a heat-resistant P-BN thin film to a thickness of about 100 μm in advance, it is possible to surely reduce the incorporation of carbon from the slide board.

As a result, in the light emitting diode (LED chip) obtained from this epitaxial wafer,
There is almost no thyristor phenomenon, and the incidence of defective products can be greatly reduced.

The present invention is not limited to the single heterostructure as described above, and the same effects can be obtained even with an epitaxial wafer having a double heterostructure.

[0023]

Next, specific examples of the present invention will be described.

(Embodiment) First, as a p-type AlGaAs layer growth solution, arsenic gallium (GaAs) polycrystal: 66 m
g / gGa, aluminum (Al): 2 mg / gGa,
A gallium solution to which zinc (Zn) as a p-type dopant: 1 mg / g Ga was added was prepared, and an n-type AlGa
As layer growth solution, arsenic gallium polycrystal: 28 mg
/ GGa, aluminum: 5 mg / gGa, and a gallium solution to which 0.001 mg / gGa of tellurium (Te) as an n-type dopant was added, and these solutions were set in a graphite carbon slide board and the substrate was set. It was set on the substrate holder.

Here, in order to prevent carbon from being mixed into the growth solution mounting portion of this slide board, P-BN
A thin (about 100 μm) coating was applied.
The substrate used was a Zn-doped p-type GaAs single crystal substrate.

Next, the slide board was set in a quartz reaction tube, the air in the reaction tube was evacuated, hydrogen gas was introduced, and the temperature of the electric furnace was raised to 960 ° C. in that state. A raw material solution was prepared by dissolving GaAs polycrystal, Al, and dopant Si in a gallium solution, and then cooling was started at a predetermined cooling rate.

In the meantime, the substrate holder is moved and the p-type Ga
An As substrate is brought into contact with a p-type AlGaAs layer growth solution to grow a p-type AlGaAs layer serving as a first layer having a thickness of about 20 μm.
An n-type AlGaAs layer serving as a second layer having a thickness of about 40 μm was grown as an As layer growth solution, thereby obtaining a single heterostructure AlGaAs epitaxial wafer for a red light emitting diode having an emission wavelength of 655 nm.

After 100 epitaxial wafers are continuously manufactured in this way, 10
The wafers were sampled to analyze the carbon concentration in the n-type AlGaAs layer, and LED chips were fabricated from the remaining 90 wafers, and their characteristics were examined.

As a result, the carbon concentration of each of the wafers according to the present embodiment is not more than the specified value of the present invention.
９9.2) × 10 ¹⁶ / cm ³ , and none of the produced LED chips showed a thyristor phenomenon.

(Comparative Example) 100 epitaxial wafers manufactured under the same manufacturing conditions as in the embodiment except that the above-mentioned P-BN thin film was not coated on the growth solution mounting portion of the slide board. The carbon concentration was measured and the characteristics of the LED chip were examined in the same manner as in the above example.

As a result, the carbon concentration is in the range of (1.3 to 2.8) × 10 ¹⁷ / cm ³ , which exceeds the specified value of the present invention. It was confirmed that chips exhibiting a thyristor phenomenon with an incidence of 0.5 to 5%.

[0032]

In summary, according to the present invention, n-type Al
The carbon concentration in the GaAs layer is set to 1.0 × 10 ¹⁷ / cm ³
Therefore, it is possible to obtain an AlGaAs epitaxial wafer for a light emitting diode having almost no p-type inversion layer region that causes a thyristor phenomenon. As a result, high quality light emitting diodes (LED chips) without thyristor phenomenon
, Etc. can be reliably provided.

[Brief description of the drawings]

FIG. 1 is an enlarged cross-sectional view showing an embodiment of an AlGaAs epitaxial wafer for light emitting diodes (single heterostructure) according to the present invention.

FIG. 2 is a graph showing carbon concentration distribution and p in an n-type AlGaAs layer.
FIG. 5 is a graph showing a relationship with a position where a pattern inversion layer occurs.

[Explanation of symbols]

 1 on a GaAs single crystal substrate 2 p-type AlGaAs layer 3 n-type AlGaAs layer

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Koya Shibata 5-1-1, Hidaka-cho, Hitachi City, Ibaraki Prefecture F-term in the Hidaka Factory, Hitachi Cable, Ltd. 5F041 AA41 CA35 CA36 CA63 5F053 AA01 BB03 BB12 BB42 DD05 FF02 GG01 HH01 HH04 JJ01 JJ03 KK01 KK04 KK07 LL02 RR01 RR03 RR11

Claims (2)

[Claims] 1. A p-type AlGaAs on a GaAs single crystal substrate.
In an AlGaAs epitaxial wafer for a light emitting diode in which an s layer and an n-type AlGaAs layer are formed by a liquid phase epitaxial method, the carbon (C) concentration in the n-type AlGaAs layer is less than 1.0 × 10 ¹⁷ / cm ³ . An AlGaAs epitaxial wafer for a light emitting diode, comprising: 2. An AlG for a light emitting diode according to claim 1.
In the method for manufacturing an aAs epitaxial wafer, the method for growing an n-type AlGaAs layer is characterized in that a carbon-made epitaxial growth jig is pre-coated before the n-type AlGaAs epitaxial layer is grown. AlGaAs
Manufacturing method of epitaxial wafer.