JP2003086835A - Semiconductor light emitting element and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the light emitting efficiency of a semiconductor light emitting element higher by improving the transmittance of the element to the light generated in a multilayered laminated stature composed of a plurality of semiconductor layers constituting the element. SOLUTION: On the light emitting surface 16 of the multilayered laminated structure 18 constituted of a substrate 11, a first semiconductor layer 12, and a second semiconductor layer 13, an antireflection filter 17 composed of a plurality of projecting sections arranged in a cycle shorter than the wavelength of the light outputted from the light emitting surface 16 is formed on the surface 16.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light emitting device and a method for manufacturing the semiconductor light emitting device.

[0002]

2. Description of the Related Art In recent years, there have been increasing social demands for semiconductor light emitting devices such as light emitting diodes (LEDs), which have advantages such as small size, light weight, and long life. The demand for efficiency is also increasing.

FIG. 1 shows a conventional LED having a double hetero structure.
It is a block diagram which shows an example. In the LED 10 shown in FIG. 1, a first semiconductor layer 2 also made of p-GaAlAs and a second semiconductor layer 3 made of n-GaAlAs are sequentially formed on a substrate 1 made of p-GaAlAs. ing. Then, on the back surface of the substrate 1, AuZ
A first electrode 4 made of n or the like is formed, and a second electrode 5 made of AuSn or the like is formed on the second semiconductor layer 3. The substrate 1, the first semiconductor layer 2, and the second semiconductor layer 3 form a multilayer laminated structure 8.

The first semiconductor layer 2 functions as a light emitting layer,
The substrate 1 and the second semiconductor layer 3 function as a conductive layer for the light emitting layer. The upper surface of the second semiconductor layer 3 constitutes the light emitting surface 6. When a predetermined voltage is applied between the first electrode 4 and the second electrode 5, a current flows through the substrate 1 and the second semiconductor layer 3 to the first semiconductor layer 2, and the current is excited to emit light. Give rise to.

At this time, for example, the light generated in the central portion of the first semiconductor layer 2 reaches the critical angle θc after being repeatedly reflected and absorbed by the electrodes as shown by an arrow in FIG. , Is taken out from the light emitting surface 6.

[0006]

In FIG. 1, an LED is used.
The refractive index n1 of the atmosphere located outside of 10 is about 1.0, and the refractive index n2 of the second semiconductor layer 3 forming the light emitting surface 6 is n2.
Is about 3.5 when composed of, for example, GaAlAs. Further, the critical angle θc is θc = sin ⁻¹ (n1 / n
2), the refractive indices n1 and n are as described above.
If the difference between 2 becomes large, the critical angle θc will decrease. As a result, the transmittance of light from the light emitting surface 6 deteriorates,
There is a problem that the light extraction efficiency is extremely reduced.

In view of such problems, it has been attempted to provide an antireflection film between the multilayer laminated structure 8 and the second electrode 5, but the material used for such an antireflection film is extremely limited. In addition, it can be used only for an extremely narrow emission wavelength. As a result, sufficient transmittance could not be realized, and improvement in light extraction efficiency was limited.

It is an object of the present invention to improve the transmittance of light generated by a multi-layered laminated structure composed of a plurality of semiconductor layers constituting a semiconductor light emitting device and to obtain a high light extraction efficiency.

[0009]

[Means for Solving the Problems] In order to achieve the above object,
The present invention is a semiconductor light emitting device including a multilayer laminated structure composed of a plurality of semiconductor layers, wherein a lattice shape is formed on a light emitting surface of the multilayer laminated structure at a cycle shorter than a wavelength of light emitted from the multilayer laminated structure. A semiconductor light emitting device, characterized in that it comprises an antireflection filter arranged.

The present inventors have conducted extensive studies to achieve the above object. As a result, they have found that the above object can be achieved by providing an antireflection filter having the above-described characteristics on the light emitting surface of a conventional semiconductor light emitting device. That is, by providing the above-described antireflection filter, the difference between the refractive index of the semiconductor material forming the light emitting surface of the multilayer laminated structure and the refractive index of the atmosphere outside the semiconductor light emitting element is complemented, and the refractive index difference is obtained. An arbitrary refractive index space that smoothly matches is formed.

Therefore, the substantial critical angle at the light emitting surface of the semiconductor light emitting device increases. Then, the transmittance of the light generated in the semiconductor light emitting element from the light emitting surface is also increased, and as a result, the light extraction efficiency is improved, and the object of the present invention can be realized.

Such an antireflection filter has higher material selectivity than conventional antireflection films,
It can be applied to a wide range of emission wavelengths.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in detail based on the embodiments of the invention. FIG. 2 is a configuration diagram showing an example of the semiconductor light emitting device of the present invention. In addition, in order to clarify the features of the present invention, FIG. 2 is drawn differently from the actual configuration.

The semiconductor light emitting device 20 shown in FIG.
On the substrate 11 made of aAlAs or the like, p
A first semiconductor layer 12 made of GaAlAs or the like and n
-The second semiconductor layer 13 made of GaAlAs or the like is sequentially provided. Then, a first electrode 14 made of AuZn or the like is formed on the back surface of the substrate 11, and a second electrode 15 made of AuSn or the like is formed on the second semiconductor layer 13 to form an LED having a double hetero structure. I am configuring.

The substrate 11, the first semiconductor layer 12, and the second
The semiconductor layer 13 constitutes a multilayer laminated structure 18. The first semiconductor layer 12 functions as a light emitting layer, and the substrate 11 and the second semiconductor layer 12
The semiconductor layer 13 functions as a conductive layer for the light emitting layer.

The second semiconductor layer 13 is formed so that its central portion is recessed, and the bottom surface in the recess functions as the light emitting surface 16. An antireflection filter 17 is formed on the light emitting surface 16. The antireflection filter 17 is composed of a plurality of convex portions arranged in a lattice with a cycle T1 in the horizontal direction and a cycle T2 in the vertical direction. Due to the method for manufacturing a semiconductor light emitting device of the present invention described below, the plurality of convex portions, that is, the antireflection filter 17 is made of the same semiconductor material as the second semiconductor layer 13, for example, p-GaAlAs. Has been done.

In the present invention, the antireflection filter 17 is used.
It is necessary that the periods T1 and T2 of the plurality of convex portions arranged in a lattice pattern that configure the above are shorter than the wavelength of the light emitted from the light emitting surface 16 of the multilayer laminated structure 18. As a result, the light is extracted from the semiconductor light emitting element 20 to the outside (atmosphere).
The difference between the refractive index n1 and the refractive index n2 of the second semiconductor layer 13 forming the light emitting surface 16 can be complemented, and an arbitrary refractive index space that smoothly matches these refractive index differences can be formed.

FIG. 3 is a conceptual diagram showing a change in the refractive index in the stacking direction of the semiconductor light emitting device 20 of the present invention shown in FIG. 2, and FIG. 4 is a conventional semiconductor light emitting device 10 shown in FIG.
FIG. 6 is a diagram showing a change in the refractive index in the stacking direction. Figure 3
2 shows the semiconductor light emitting device 2 of FIG. 2 according to the present invention.
At 0, the antireflection filter 17 continuously changes the refractive index in the stacking direction so as to fill the difference between the refractive index n2 of the second semiconductor layer 13 and the refractive index n1 of the outside (atmosphere). A space is formed.

On the other hand, as shown in FIG. 4, in the conventional semiconductor light emitting device 10 having no antireflection filter, the refractive index becomes stepwise from the second semiconductor layer 13 toward the outside (atmosphere). It will change rapidly.

Therefore, as described above, in the conventional semiconductor light emitting device 10, the critical angle θ with respect to the light emitting surface 6 is set.
On the other hand, in the semiconductor light emitting element 20 according to the present invention, the change in refractive index with respect to the outside (atmosphere) is small, whereas the substantial critical angle with respect to the light emitting surface 16 increases. As a result, the transmittance of the light emitting surface 16 increases and the light extraction efficiency to the outside (atmosphere) also increases.

The periods T1 and T2 of the plurality of convex portions constituting the antireflection filter 17 may be different, but usually they are substantially the same in order to simplify the manufacturing process.

The height h of the antireflection filter 17 is
The thickness is preferably 100 nm to 400 nm, more preferably 200 nm to 400 nm. This makes it possible to function as an antireflection filter for almost all the light in the visible light region, and the above-described effects can be more remarkably exhibited. The lower limit of the height h is limited mainly by the current fine processing technology.

Further, the periods T1 and T2 of the plurality of convex portions constituting the antireflection filter 17 are not particularly limited as long as they are shorter than the wavelength of the light emitted from the light emitting surface 16.
100 nm to 400 to deal with all visible light
Set to the range of nm. As a result, the antireflection filter 17 can be easily manufactured, and at the same time, the above-described effects can be obtained for a wide range of emission wavelengths.

The thicknesses of the first semiconductor layer 12 and the second semiconductor layer 13 may be arbitrarily formed depending on the composition of each layer, the film forming technique, the desired physical characteristics, and the like. it can.

Next, a method of manufacturing the semiconductor light emitting device 20 shown in FIG. 2 will be described. 5 to 10 are cross-sectional views for explaining the manufacturing process of the semiconductor light emitting device 20. In these drawings, A of the semiconductor light emitting device 20
It shows that the semiconductor light emitting elements are sequentially formed in the cross section including the -A line.

First, as shown in FIG. 5, the first semiconductor layer 12 and the second semiconductor layer 13 are formed on the substrate 11.
It is formed using a known film forming technique such as a CVD method or an epitaxial growth method. Then, as shown in FIG.
Forming a first electrode 14 on the back surface of the second semiconductor layer 13
The second electrode 15 is formed on top. Then, as shown in FIG. 7, an electron beam resist film 21 is formed on the second semiconductor layer 13 so as to cover the second electrode 15 by a spin coating method or the like, for example, with a thickness of 0.1 μm to 0.4 μm. To form.

Next, as shown in FIG. 8, the resist film 2
The resist pattern 22 is formed by performing an electron beam drawing process on 1 and then performing a developing process. Next, as shown in FIG. 9, the second semiconductor layer 13 is directly etched by using a predetermined etching gas and through the resist pattern 22 to form the antireflection filter 17. . Then
As shown in FIG. 10, the remaining resist pattern 22 is removed by using an organic solvent or the like to obtain the semiconductor light emitting device 20 having the antireflection filter 17.

The above-mentioned etching treatment is preferably carried out by using the atomic etching species obtained by decomposing the predetermined etching gas into an atomic shape by electric discharge. As a result, the etching treatment of the second semiconductor layer 13 can be performed more effectively, and the antireflection filter 17 having the height h described above can be obtained in a short time.

It is preferable that the etching gas is composed of a plurality of halogen gases having different etching characteristics, and the halogen gases are alternately used. For example, SF ₆ gas and Cl ₂ gas are used alternately. SF ₆ gas has excellent lateral etching characteristics,
Cl ₂ gas has excellent etching characteristics in the depth direction. Therefore, by using both of them in combination and performing the etching treatment by alternately using them, it is possible to easily form a plurality of convex portions having an excellent aspect ratio and sufficiently functioning as an antireflection filter.

When the aspect ratios of the plurality of convex portions are small, these convex portions are not arranged substantially in a grid and may not function as an antireflection filter.

Further, even when a plurality of halogen-based gases such as SF ₆ gas and Cl ₂ gas are used, it is preferable to use them as an etching species formed by atomically decomposing them by discharge, but they are decomposed atomically. The discharge conditions to be applied differ for each gas.

[0032]

EXAMPLE In this example, a semiconductor light emitting device 20 as shown in FIG. 2 was produced according to the steps shown in FIGS. The substrate 11 was made of p-GaAlAs, and the first semiconductor layer 12 was made of p-GaAlAs with a thickness of 0.35 μm. The second semiconductor layer 13 is composed of 160 μm thick n-GaAlAs. The thickness of the resist film 21 is 0.4 μm.

Further, the etching of the second semiconductor layer 13 through the etching pattern is performed by using SF ₆ gas and Cl.
₂ gas was used in order of SF ₆ gas, Cl ₂ gas, and SF ₆ gas, and it carried out in 3 steps. These etching gases were used after being decomposed into atoms by discharge.

FIG. 11 is an SEM photograph showing a part of the antireflection filter 17 thus formed. Figure 11
As is apparent from the above, it is understood that the antireflection filter 17 is formed of a plurality of convex portions arranged in a grid pattern. Further, it can be seen that the arrangement period of the plurality of convex portions is about 200 nm in both the horizontal and vertical directions and the height is about 275 nm.

FIG. 12 is a graph showing the relative light emission intensity of the semiconductor light emitting device 20 manufactured as described above. In FIG. 12, an angle of 0 degree indicates a direction (normal direction) perpendicular to the light emitting surface 16, and the light emitting surface 16 increases as the angle increases.
It is shown that it is inclined toward the light emitting surface 16 from the normal direction to. The relative intensity is the intensity of the light output through the antireflection filter divided by the intensity of the light output without the antireflection filter.

As is apparent from FIG. 12, the measurement angle of 4
It can be seen that light is uniformly output up to about 0 degree, and the substantial critical angle with respect to the light emitting surface 16 exhibits a value of at least about 40 degrees. Furthermore, as shown in FIG.
The critical angle θc of the semiconductor light emitting device made of AlAs is about 16
It can be seen that the semiconductor light emitting device 20 obtained in this example has a substantial critical angle of about 2 times or more in consideration of the fact that the degree is about the degree.

FIG. 13 is a graph showing the emission spectrum (solid line) of the semiconductor light emitting device. In addition, the emission spectrum (dotted line) of the semiconductor light emitting element which does not have the antireflection filter manufactured under the same conditions is also shown.

As is clear from FIG. 13, the semiconductor light emitting device of this embodiment having the antireflection filter has an emission intensity increased by about 30% as compared with the semiconductor light emitting device having no antireflection filter. That is, it can be seen that the transmittance at the light emitting surface 16 is increased and the light extraction efficiency is increased.
Furthermore, in the semiconductor light emitting device of this example, the half-value width of the peak wavelength is also increased, and it can be seen that it can be suitably used in a wide wavelength band.

Although the present invention has been described in detail based on the embodiments of the invention with reference to specific examples, the present invention is not limited to the above contents and does not depart from the scope of the present invention. , All modifications and changes are possible.

For example, in the above description, the antireflection filter 17 is manufactured by directly etching the second semiconductor layer 13. However, an additional layer is formed on the second semiconductor layer 13, and this layer is formed. Alternatively, the second semiconductor layer 13 can be manufactured separately from the second semiconductor layer 13 by performing an etching process.

Further, when the resist pattern 21 is formed, laser interferometry or a stepper can be used instead of the electron beam drawing process. Further, although the convex portion forming the antireflection filter 17 has a tapered shape, it can have any other shape.

[0042]

As described above, according to the present invention,
It is possible to provide a semiconductor light emitting device having an excellent light extraction efficiency by increasing the substantial critical angle of the light emitting surface to improve the transmittance of the emission wavelength.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an example of a conventional semiconductor light emitting device.

FIG. 2 is a perspective view showing an example of a semiconductor light emitting device of the present invention.

FIG. 3 is a conceptual diagram showing changes in the refractive index in the stacking direction in the semiconductor light emitting device of the present invention.

FIG. 4 is a conceptual diagram showing a change in refractive index in a stacking direction in a conventional semiconductor light emitting device.

FIG. 5 is a cross-sectional view showing one step in a method for manufacturing a semiconductor light emitting device of the present invention.

6 is a cross-sectional view showing a step subsequent to the step shown in FIG.

7 is a cross-sectional view showing a step subsequent to the step shown in FIG.

8 is a sectional view showing a step subsequent to the step shown in FIG. 7. FIG.

9 is a cross-sectional view showing a step subsequent to the step shown in FIG.

FIG. 10 is a cross-sectional view showing a step next to the step shown in FIG. 9.

FIG. 11 is an SEM photograph showing a part of the antireflection filter of the semiconductor light emitting device of the present invention.

FIG. 12 is a graph showing the relative light emission intensity of the semiconductor light emitting device of the present invention.

FIG. 13 is a graph showing an emission spectrum of the semiconductor light emitting device of the present invention.

[Explanation of symbols]

1, 11 substrate 2, 12 First semiconductor layer 3, 13 Second semiconductor layer 4, 14 First electrode 5, 15 Second electrode 6, 16 light emitting surface 8, 18 Multi-layer laminated structure 10, 20 Semiconductor light emitting device 17 Anti-reflection filter

Claims (8)

[Claims] 1. A semiconductor light-emitting device including a multi-layer laminated structure composed of a plurality of semiconductor layers, wherein a grating is formed on a light-emitting surface of the multi-layer laminated structure at a period shorter than a wavelength of light emitted from the multi-layer laminated structure. A semiconductor light-emitting device, comprising an antireflection filter composed of a plurality of convex portions arranged in a line. 2. The semiconductor light emitting device according to claim 1, wherein the antireflection filter is made of the same semiconductor material as a semiconductor layer forming the light emitting surface of the multilayer laminated structure. . 3. The semiconductor light emitting device according to claim 1, wherein the height of the plurality of convex portions forming the antireflection filter is 100 nm to 400 nm. 4. The semiconductor light emitting device according to claim 1, wherein the plurality of convex portions forming the antireflection filter have a lattice period of 100 nm to 400 nm. 5. A step of forming a multilayer laminated structure composed of a plurality of semiconductor layers, a step of forming an electron beam resist film on a light emitting surface of the multilayer laminated structure, and an electron beam drawing and developing of the resist film. A step of forming a predetermined resist pattern by etching the semiconductor layer forming the light emitting surface of the multilayer laminated structure through the resist pattern, and the wavelength of light emitted from the multilayer laminated structure is shorter than the wavelength of light emitted from the multilayer laminated structure. And a step of forming antireflection filters arranged in a grid pattern at regular intervals, the method for manufacturing a semiconductor light emitting device. 6. The etching of the semiconductor layer constituting the light emitting surface of the multilayer laminated structure is performed using an atomic etching species formed by atomically decomposing an etching gas by discharging. The method for manufacturing a semiconductor light emitting device according to claim 5. 7. The semiconductor light emitting device according to claim 6, wherein the etching gas comprises a plurality of halogen-based gases having different etching characteristics, and the etching is performed by alternately using the plurality of halogen-based gases. Device manufacturing method. 8. The method for manufacturing a semiconductor light emitting device according to claim 7, wherein the plurality of halogen-based gases are composed of SF ₆ gas and Cl ₂ gas.