JP2000312029A - Semiconductor light emitting element and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the light emitting efficiency of a semiconductor light emitting element by epitaxially thickly growing GaP buffer layers on both surfaces of a GaP substrate and a light emitting layer forming section on one of the buffer layers. SOLUTION: On both surface of a thin GaP substrate 1, epitaxially grown thick surface and rear GaP buffer layers 2 and 3 are respectively formed. On the surface buffer layer 2, a semiconductor-laminated section constituting a light emitting layer forming section 9 is provided. The section 9 is formed by successively laminating an n-type layer having a carrier concentration of about 1×10 to 2×10 cm and a thickness of about 25-40 μm, another n-type layer 5 having a carrier concentration of 1×10 to 3×10 cm and a thickness of about 10-15 μm, and a p-type layer 6 having a carrier concentration of about 1×10 to 2×10 cm and a thickness of about 20-25 μm upon another.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a green to yellowish green semiconductor light emitting device using a GaP compound semiconductor and a method for producing the same. More specifically, the present invention relates to a semiconductor light emitting device made of a GaP compound and having improved light extraction efficiency to the outside, and a method of manufacturing the same.

[0002]

2. Description of the Related Art As shown in FIG. 4, a conventional semiconductor light emitting device using a GaP compound semiconductor is formed on an n-type GaP n-type layer 22 and a GaP n-type layer 22 on a semiconductor substrate 21 made of, for example, n-type GaP. Each of the p-type layers 23 is epitaxially grown, and the light emitting layer forming portion 24 is formed by the pn junction. The p-side electrode 26 mainly made of Au and the semiconductor substrate 2
Each of the n-side electrodes 27 mainly made of Au is provided on the back surface of the substrate 1 and is chipped from the wafer.

Conventionally, a green semiconductor light emitting device using GaP is formed on a GaP substrate by liquid phase growth or the like.
Since aP does not absorb the light emitted, light emitted at the pn junction and traveling to the substrate side is not absorbed and light emitted from the side surface or light reflected on the substrate side can be used. Although the internal luminous efficiency was low, the external differential quantum efficiency, which is the extraction efficiency to the outside, was considered to be relatively good. However, since the crystallinity of the GaP substrate is not good, the light extraction is not always sufficient. To improve the light extraction efficiency, as shown in FIG.
The GaP buffer layer 25 is formed thick on the P substrate 21 by liquid phase epitaxy, and the GaP substrate is
By reducing the ratio of the thickness of the P substrate 21 to the thickness of the entire chip, a measure may be taken to extract more light from the side surface of a light emitting element chip (hereinafter, referred to as an LED chip). This is because the refractive index of the semiconductor layer is considerably larger than that of the surrounding air, etc., and it is difficult to extract light from the upper surface of the laminated semiconductor layer to the front side by total reflection at the surface side of the semiconductor layer and also to obtain a lamp-type light emitting element. In this method, the LED chip is die-bonded to the bowl-shaped recess, and the light emitted from the side is reflected by the inner wall of the recess toward the front side and can be used.

[0004]

As described above, in a conventional semiconductor light emitting device having a GaP layer grown thereon, a GaP buffer layer is provided by a liquid phase growth method in order to minimize the influence of light loss due to a GaP substrate. Is considered. However, the growth of the semiconductor layer by the liquid phase epitaxy is based on Ga
Crystal growth is carried out by gradually lowering the temperature while making contact with the melt. When the temperature is lowered to about 800 ° C., growth stops. Therefore, the thickness of the semiconductor layer grown by one liquid phase growth method is about 100 to 150 μm. The thicker the buffer layer, the thinner the GaP substrate with poor crystallinity and the higher the external differential quantum efficiency. However, as described above, it is necessary to grow the substrate by a single liquid phase growth method. However, since there is a limit to the thickness of the buffer layer, if the thickness of the buffer layer is to be increased, the liquid phase growth for growing the buffer layer must be repeated twice or more, which increases the number of steps and increases the cost. There is.

[0005] The present invention has been made in view of such a situation, and the thickness of the buffer layer relative to the thickness of the entire semiconductor chip is increased while performing the step of growing the buffer layer by the liquid phase growth method in one step. Provided are a semiconductor light emitting device and a method for manufacturing the same, which can improve the light extraction efficiency to the outside by increasing the ratio and improve the external differential quantum efficiency of a yellow to green semiconductor light emitting device using a GaP semiconductor. The purpose is to:

[0006]

According to the present invention, there is provided a semiconductor light emitting device comprising: a GaP substrate; a buffer layer made of GaP which is epitaxially grown on both sides of the GaP substrate; and a GaP substrate which is epitaxially grown on one side of the buffer layer.
And a semiconductor laminated portion having an n-type layer and a p-type layer, and constituting a light emitting layer forming portion.

[0007] With this structure, the GaP substrate has a good crystallinity and a thick GaP layer epitaxially grown by the liquid phase epitaxy on both surfaces of the GaP substrate. Light extraction efficiency can be improved.

The manufacturing method of the semiconductor light emitting device of the present invention is GaP.
At least the back side of the substrate is melted back to make it thinner, and a buffer layer made of GaP is epitaxially grown on both sides of the thinned GaP substrate, and a light emitting layer forming part is formed on the surface of the buffer layer on the front side of the GaP substrate. Constituent n
The semiconductor laminated portion including the p-type layer and the p-type layer is epitaxially grown by a liquid phase growth method.

According to this manufacturing method, when growing a buffer layer, a GaP substrate having poor crystallinity is thinned by meltback, so that the GaP material is not wasted and the buffer is formed not only on the front surface but also on the back surface. Since the layer is epitaxially grown, a thick GaP layer with good crystallinity can be grown on both surfaces in the same time by one liquid phase growth. Therefore, even if the overall thickness does not change,
The conventional GaP substrate is very thin and has good crystallinity.
Since the buffer layer made of P is formed thick, light attenuation can be greatly reduced, and external differential quantum efficiency can be improved.

[0010]

Next, a semiconductor light emitting device of the present invention and a method of manufacturing the same will be described with reference to the drawings.

FIG. 1 is a cross-sectional view of a semiconductor light emitting device chip (hereinafter referred to as an LED chip) according to an embodiment of the present invention.
The surface buffer layer 2 and the back surface buffer layer 3 made of GaP, which are made thick and epitaxially grown on both sides thereof, are provided. Then, on the surface buffer layer 2, a semiconductor laminated portion having an n-type layer 5 and a p-type layer 6 made of GaP and constituting a light emitting layer forming portion 9 is provided.

As the GaP substrate 1, a substrate having a thickness of about 300 μm is used at first.
The thickness is reduced to about μm. Following the meltback, the buffer layers 2 and 3 made of GaP are grown by liquid phase growth, so that the surface buffer layer 2 has a carrier concentration of 1 ×.
In 10 ¹⁷ ~3 × 10 ¹⁷ m about ^-3 to about 50μm thick, the back surface buffer layer 3, a carrier concentration of 1 × 10 ¹⁷ ~
Each is grown to a thickness of about 150 μm at about 3 × 10 ¹⁷ cm ⁻³ . Although the front buffer layer 2 is formed thin and the back buffer layer 3 is formed thick even when the growth is performed for the same period of time, as shown in FIG. This is because, in the Ga melt in the interposed region, the GaP concentration becomes higher toward the upper side.

In the example shown in FIG. 1, the light emitting layer forming section 9 has an n ^{+ -type} layer 4 having a carrier concentration of about 1 × 10 ¹⁷ to 2 × 10 ¹⁷ cm ^{-3 and} a thickness of about 25 to 40 μm. The carrier concentration is about 1 × 10 ^{16 to} 3 × 10 ¹⁶ cm ⁻³ ,
An n ⁻ -type layer 5 having a thickness of about 15 μm and a carrier concentration of 1
In × 10 ¹⁸ ~2 × 10 ¹⁸ cm about ^-3, it is made of p-type layer 6 which a thickness of about 20 to 25 m.

To manufacture this LED chip, as shown in FIG. 2, a carbon boat 11 made of a material that can withstand a high temperature of about 1100 ° C.
A step 12 for mounting the substrate 1 is provided, and when the GaP substrate 1 is mounted on the step 12, the GaP substrate 1
Using a boat provided with an opening 13 so that the Ga melt 15 is also in contact with the back surface of the substrate, GaP and Ga melt are brought into contact with each other at 900 ° C. to form a saturated melt and poured into the GaP substrate 1. . Then, the substrate temperature is set to 1000 to 105
When the temperature is raised to about 0 ° C., the Ga melt 15 becomes unsaturated, so that the GaP substrate 1 is melted back and dissolved in the Ga melt to become thin. At this time, the higher the concentration of P, the lighter the Ga melt 15 is, the lighter it becomes, and the easier it is to gather in the upper layer.
The melt 15 is likely to be in an unsaturated state. Therefore, when the above-described temperature is maintained, the back side of the GaP substrate 1 (the lower side in the figure)
Stops at a certain meltback, and the surface side of the GaP substrate 1 is melted back relatively much, so that the GaP substrate 1 becomes thin.

Due to the melt back, the GaP substrate 1 has 30
After the thickness is reduced from about 0 μm to about 50 to 60 μm, the substrate temperature is decreased at a rate of about 1 to 3 ° C./min. Then, the Ga melt 15 becomes supersaturated, and GaP crystals grow on the GaP substrate 1. By continuing this until the substrate temperature becomes about 800 ° C., as shown in FIG. 1, the front buffer layer 2 grows about 50 μm, and the back buffer layer 3 grows about 150 μm on the back surface of the GaP substrate 1. Then, the substrate temperature is lowered to room temperature and then taken out (the substrate is not grown at a temperature lower than 800 ° C.). The reason why the front surface buffer layer 2 is thin and the back surface buffer layer 3 is thick is as follows.
As described above, the upper layer of the Ga melt 15 (Ga
The backside of the P substrate 1) has a high GaP concentration, and the lower layer (GaP
This is because the GaP concentration of the surface side of the substrate 1) is low.

Thereafter, the GaP substrate 1 is placed in a liquid phase growth apparatus so that only the surface buffer layer 2 side of the GaP substrate 1 comes into contact with the Ga melt. By doing so, the n ^{+ -type} GaP layer 4, the n ⁻ -type GaP layer 5, and the p-type GaP layer 6 are grown to the above-described carrier concentration and thickness, and the light-emitting layer forming section 9 is laminated.

By utilizing the aforementioned properties of the Ga melt, FIG.
As shown in FIG. 2, for example, the carbon boats 11 are stacked in multiple stages, and the GaP layer
By bringing the GaP layer substrate 1 into contact with the melt, the temperature is first raised and the GaP layer substrate 1 is melted back, and then the temperature is gradually lowered. 3 can be grown thick by a liquid phase growth method.

According to the present invention, the GaP layer is provided not only on the front side but also on the back side of the GaP layer substrate by the liquid phase growth method as a buffer layer, so that the semiconductor has good crystallinity and low light loss. Layers can be grown thick. In addition, since they are provided on both surfaces of the substrate, they can be grown simultaneously, and a thick epitaxial growth layer can be obtained in a short time in one growth step. As a result, the ratio of the thickness of the GaP layer having good crystallinity to the thickness of the entire chip is increased, light can be efficiently extracted from the side of the LED chip, and the external differential quantum efficiency can be greatly improved. it can. In this case, by making the GaP substrate 1 thin before growth, the ratio of the GaP substrate having poorer crystallinity can be further reduced.

Further, according to the manufacturing method of the present invention, the GaP substrate 1 having poor crystallinity can be melt-backed and thinned just by increasing the temperature in the growth apparatus before growing the buffer layer. The thickness of the GaP substrate can be easily reduced without mechanically and chemically polishing the GaP substrate, and the melted-back GaP can be used as a new material for epitaxial growth. as a result,
GaP with excellent crystallinity without wasting GaP material
The layer can be formed thick. Therefore, the number of growth steps and the growth material can be significantly reduced, and a semiconductor light emitting device having high external differential quantum efficiency and high characteristics can be obtained at a low cost while significantly reducing the cost.

In the above-described example, the light emitting layer forming portion 9 is n
^Although the lamination process of the ^{+ -type} layer, the n ⁻ -type layer, and the p-type layer has been described, other structures such as a structure having only a simple n-type layer and a p-type layer may be used.

[0021]

According to the present invention, the number of steps in the growth process of the buffer layer and the material to be grown can be greatly reduced, which greatly contributes to the cost reduction and the light extraction efficiency to the outside (external differential quantum efficiency). Is improved by 20% or more, and an inexpensive and high-performance yellow to green semiconductor light emitting device can be obtained.

[Brief description of the drawings]

FIG. 1 shows an LED according to an embodiment of the semiconductor light emitting device of the present invention.
FIG. 3 is an explanatory sectional view of a chip.

FIG. 2 is an explanatory diagram of an example of an apparatus for growing the buffer layer of FIG.

3 is an explanatory diagram of an example in which the boats of FIG. 2 are stacked in multiple stages and buffer layers are grown on both surfaces of a large number of wafers at a time.

FIG. 4 is an explanatory diagram of a structural example of an LED chip using a conventional GaP layer.

FIG. 5 is a diagram showing an example of the structure of an LED chip that improves external differential quantum efficiency with a conventional LED chip.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 GaP substrate 2 front buffer layer 3 back buffer layer 4 n ^{+ -type} GaP layer 5 n ^--type GaP layer 6 p-type GaP layer 9 light-emitting layer forming part

Claims (2)

[Claims] 1. A semiconductor device comprising: a GaP substrate; a buffer epitaxial growth layer of GaP thickly grown on both sides of the GaP substrate; and an n-type layer and a p-type layer of GaP epitaxially grown on one side of the buffer epitaxial growth layer. A semiconductor light emitting element comprising: a light emitting layer forming portion; At least the back surface of the GaP substrate is etched back to make it thinner, and a buffer layer made of GaP is epitaxially grown on both surfaces of the thinned GaP substrate. A method of manufacturing a semiconductor light emitting device, comprising: epitaxially growing a semiconductor laminated portion including an n-type layer and a p-type layer constituting a light emitting layer forming portion by a liquid phase epitaxy method.