JPH0685316A - Semiconductor light emitting device - Google Patents

Abstract

PURPOSE:To provide a semiconductor light emitting device having a reflection layer wherein the maximum reflectance is maintained and further the half-width of the reflection spectrum is widened. CONSTITUTION:A semiconductor light emitting device 1 has, between a clad layer 6 and buffer layer 3, a superposed multilayer reflection layer 4 composed of superposed multilayer reflection layers 4a and 4b with their thickness intentionally varied. For example, the multilayer reflection layer 4a is formed by superposing 25 sets of an Al0.1Ga0.9As semiconductor layer of 76nm in thickness and an Al0.7Ga0.3As semiconductor layer of 80nm in thickness. The multilayer reflection layer 4b is formed by superposing 25 sets of an Al0.1Ga0.9As semiconductor layer of 70nm in thickness and an Al0.7Ga0.3As semiconductor layer of 75nm in thickness. The reflection center wavelength of these multilayer reflection layers 4a and 4b is 850nm and 910nm, respectively. The half-width of both is 70-80nm or so; however, it is widened to 120nm by superposition.

Description

Detailed Description of the Invention

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

[0001]

2. Description of the Related Art In recent years, surface-emitting type semiconductor light-emitting devices have been widely used as optical communication and display devices. These light emitting diodes are used as semiconductor light emitting devices by forming a PN junction on a GaAs substrate crystal or the like by using a crystal growth method such as LPE (liquid phase epitaxy) method or MOCVD (metal organic chemical vapor deposition) method. Being manufactured. However, since the GaAs substrate crystal has a smaller bandgap than the semiconductor crystal forming the PN junction, most of the light that reaches the substrate crystal is absorbed. Therefore, conventionally, the substrate crystal is removed by etching to prevent the loss of light emission output. As described above, in order to remove the substrate crystal by etching, it is necessary to form a semiconductor crystal layer having a film thickness of about 100 μm or more, but conventionally, a thick film is formed using a thick film growth technique such as the LPE method. Was there.

However, in recent years, the MOCVD method and the MBE method, which have better controllability and uniformity of composition and film thickness than the LPE method,
Attempts have been made to manufacture semiconductor light emitting devices using the (molecular beam epitaxy) method. However,
These MOCVD method and MBE method are excellent in thin film controllability and reproducibility, but conversely cannot grow a thick film until the substrate crystal can be removed. Therefore, MOCVD method and M
In manufacturing a semiconductor light emitting device by the BE method,
In recent years, a multilayer reflective layer has attracted attention for improving the output of a semiconductor light emitting device. Hereinafter, a conventional example of a semiconductor light emitting device provided with a multilayer reflective film, particularly a light emitting diode, will be described with reference to the drawings.

FIG. 5 is a perspective view showing an example of the structure of a conventional light emitting diode provided with a multilayer reflective film. In FIG. 5, the light emitting diode 11 has a structure in which a buffer layer 3, a multilayer reflective layer 10, a clad layer 6, an active layer 7, and a clad layer 8 are sequentially laminated on a substrate crystal 2. The multilayer reflective layer 10 is formed by stacking 25 GaAs layers and AlGaAs layers, for example. This multilayer reflective layer 10
Is a stacked semiconductor layer, that is, a GaAs layer and an AlGaAs
The greater the difference in refractive index from the layers and the greater the number of layers, the more improved the reflection characteristics. The reflection center wavelength λ _p of the multilayer reflective layer 10 thus laminated is given by λ _p = 4 nd, where d is the thickness of one semiconductor crystal layer to be laminated and n is the refractive index. The reflection spectrum of this multilayer reflective layer 10 is shown in FIG. According to FIG. 6, the reflectance near the reflection center wavelength of 880 nm is 99% or more, which is a good value.

In the light emitting diode 11 provided with such a multilayer reflection layer 10, the light emitted to the clad layer 8 side in the active layer 7 is directly output from the light emitting surface 9, but the light output to the clad layer 6 side is The light is reflected by the multilayer reflective layer 10 and output from the light emitting surface 9. FIG. 7 shows this light emitting diode 1.
FIG. 3 is a diagram showing light emission outputs of 1 (solid line) and a light emitting diode having no multilayer reflection layer (dashed line). According to FIG. 7, the light emission output of the light emitting diode 11 is significantly improved in the vicinity of the reflection center wavelength of 880 nm of the multilayer reflection layer 10 as compared with the light emitting diode without the multilayer reflection layer 11.

By thus providing the multilayer reflective layer 10 between the substrate crystal 2 and the active layer 7, the light emitted from the active layer 7 is reflected by the multilayer reflective layer 10 before reaching the substrate crystal 2. Therefore, it is possible to eliminate the loss of light emission output caused by the substrate crystal absorbing light. As a result, a high-power light emitting diode could be manufactured without removing the substrate crystal 2.

[0006]

However, according to the light emitting diode 11 as described above, as shown in FIG.
In the vicinity of the reflection center wavelength (880 nm) of the multilayer reflective layer 10, the maximum reflectance is 99% or more. However, the half-value width of the reflection spectrum of the multilayer reflective layer 10 is 70 to 8
It is about 0 nm. As described above, the reflective characteristics of the multilayer reflective layer have a large difference in refractive index from the semiconductor layers to be laminated, and the greater the number of laminated layers, the better the reflective characteristics. There is a proper value from the problem of
In the multilayer reflective layer having such a structure, the above values are the limits. Therefore, as shown by the alternate long and short dash line in FIG. 7, the actual emission spectrum width of the active layer 7 is generally larger. Therefore, even if such a multilayer reflective layer 10 is actually incorporated in a light emitting diode, the emission pattern is On the short-wavelength side and the long-wavelength side, the light is absorbed by the substrate crystal and the gain sharply decreases. Further, the reflection center wavelength λ _p of the reflection spectrum of the multilayer reflection layer 10 is λ _p = 4 as described above.
Although represented by nd, if the film thickness deviates by about 1 to 2% at the stage of growth of the semiconductor layer of the multilayer reflective layer 10, the multilayer reflective layer 10
Since the center wavelength of the reflection of the reflection spectrum of is shifted, the efficient reflection of light emission is impaired.

Therefore, the present invention has been made by paying attention to the above-mentioned point, and by performing the reflection covering a wide emission wavelength of the active layer by widening the half value width of the reflection spectrum while maintaining the maximum reflectance. Another object of the present invention is to provide a semiconductor light emitting device provided with a multilayer reflective layer that realizes efficient reflection characteristics even when the film thickness deviates by 1 to 2%.

[0008]

As a means for achieving the above object, the present invention provides semiconductor light emission in which light generated in an active layer is output from a light extraction surface formed on a surface parallel to the active layer. In the device, the semiconductor light emitting device has a reflection layer for reflecting, to the light extraction surface side, the light emitted from the active layer on the side opposite to the light extraction surface, and the reflection layer. Is a multi-layered multi-layered reflection layer in which at least two or more multi-layered reflection layers in which a plurality of semiconductor crystal layers having different refractive indices are alternately laminated are made to have different reflection center wavelengths. It is intended to provide a characteristic semiconductor light emitting device.

As a means for achieving the above-mentioned object, the present invention provides the semiconductor light emitting device, wherein the multiplex multilayer reflective layer is formed by changing the thickness of each multilayer reflective layer. An object of the present invention is to provide a semiconductor light emitting device characterized in that a multilayer reflective layer formed by layers is formed by being multiplexed.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings, taking a light emitting diode as an example as in the conventional example. The light emitting diode 1 described in the above-mentioned conventional example
The description of the same parts as 1 will be omitted. Further, the emission center wavelength of the active layer 7 is set to 880 nm as in the conventional example.

FIG. 1 is a schematic perspective view showing the structure of a semiconductor light emitting device according to an embodiment of the present invention. In FIG. 1, the light emitting diode 1 includes a multilayer reflective layer 4 a and a multilayer reflective layer 4 b in which the film thickness is intentionally changed between the cladding layer 6 and the buffer layer 3.
There is provided a multi-layered multilayer reflective layer 4 in which and are multiplexed. Here, the multilayer reflective layer 4a includes, for example, an Al _0.1 Ga _0.9 As semiconductor layer 76 nm and an Al _0.7 Ga _0.3 As semiconductor layer 80n.
It is a multilayer reflective layer 4a in which 25 sets of m and m are stacked. The multilayer reflective layer 4b is made of Al _0.1 Ga _0.9 As semiconductor layer 70 nm and Al _0.7 Ga _0.3 As semiconductor layer 75 nm.
It is a multilayer reflective layer 4b in which 25 sets are laminated with 1 set as a set.
The reflection center wavelengths of the multilayer reflection layers 4a and 4b thus formed are 850 nm and 910 nm, respectively, and the reflection spectra thereof are shown in FIGS. 2 (A) and 2 (B).

As shown in FIGS. 2A and 2B, the half-value widths of the multilayer reflective layers 4a and 4b are 70 to 80 nm, and these multilayer reflective layers 4a and 4b are as shown in FIG. 3 has a reflection center wavelength of 880 nm as shown in FIG.
The reflection spectrum has a half width of 120 nm. That is, the reflection spectrum of the multiplexed multilayer reflective layer 4 is
It is a combination of the reflection spectra of a and 4b. Therefore, the film thickness d of the multilayer reflective layers 4a and 4b is represented by λ _p = 4nd as described above.
The film thickness d of a and 4b is the same as the multilayer reflective layer 4a and the multilayer reflective layer 4b.
When the multi-layered multilayer reflection layer 4 is formed by multiplexing and, the highest reflectance portion of the reflection spectrum is selected to be linear as shown in FIG. By thus widening the half-value width of the reflection spectrum of the reflective layer, it is possible to improve the emission output of almost the entire emission of the active layer 7, as shown in FIG. Since the full width at half maximum is wide, there is no reduction in light emission output due to the film thickness deviation.

In the present embodiment, the light emitting diode has been described as an example, but the present invention is not limited to this, and can be used in other semiconductor light emitting devices.
It can also be used in the case of forming an array of semiconductor light-emitting devices incorporating the reflection layer of the present invention on the substrate crystal. Further, although the present embodiment is a multiplex multilayer reflective layer in which the multiple multilayer reflective layers are doubled, it is possible to obtain a multiple multilayer reflective layer having a wider half width by further multiplexing. The specific numbers (film thickness, number of layers, etc.) used in this example are
It is an example used for explanation, and it goes without saying that the present invention is not limited to the numerical values.

[0014]

As described above, according to the semiconductor light emitting device of the present invention, the full width at half maximum of the reflection spectrum can be widened while maintaining the maximum reflectance, so that the light emission of the light emitting layer is covered over almost the entire area. Therefore, a high-output semiconductor light-emitting device with high luminous efficiency can be obtained. In addition, since the full width at half maximum can be widened, there is an effect that the light emission output of the semiconductor light emitting device does not suddenly decrease even if the film thickness deviates by 1 to 2% at the stage of crystal growth of the reflective layer.

[Brief description of drawings]

FIG. 1 is a schematic perspective view showing the structure of a semiconductor light emitting device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a reflection spectrum of each multilayer reflective layer of the multiplexed multilayer reflective layer of the semiconductor light emitting device in FIG.

FIG. 3 is a diagram showing a reflection spectrum of a multiple reflection layer of the semiconductor light emitting device in FIG.

FIG. 4 is a diagram showing light emission outputs of the semiconductor light emitting device in FIG. 1 and a light emitting diode having no reflective layer.

FIG. 5 is a schematic perspective view showing an example of a structure of a conventional semiconductor light emitting device.

6 is a diagram showing a reflection spectrum of a multilayer reflective layer of the semiconductor light emitting device in FIG.

7 is a diagram showing the light emission output of the semiconductor light emitting device in FIG. 5 and a light emitting diode not provided with a reflective layer.

[Explanation of symbols]

 1 Semiconductor Light Emitting Device 2 Substrate Crystal 3 Buffer Layers 4a, 4b Multilayer Reflective Layer 4 Multiplexed Multilayer Reflective Layer 6,8 Cladding Layer 7 Active Layer 9 Light Emitting Surface

Claims (2)

[Claims] 1. A semiconductor light emitting device in which light emitted in an active layer is output from a light extraction surface formed on a surface parallel to the active layer, wherein the semiconductor light emitting device is one of the light emitted from the active layer. And a reflection layer for reflecting the light emitted on the side opposite to the light extraction surface to the light extraction surface side, and the reflection layer comprises at least two or more semiconductor crystal layers having different refractive indexes alternately. 1. A semiconductor light emitting device, comprising: a multi-layered multi-layered reflective layer in which at least two multi-layered multi-layered reflective layers having different reflection center wavelengths are multiplexed. 2. The semiconductor light emitting device according to claim 1, wherein the multiplex multilayer reflective layer is a multiplex multilayer reflective layer formed of the semiconductor crystal layers that are laminated by changing only the thickness of each multilayer reflective layer. A semiconductor light-emitting device characterized by being formed as follows. [0001]