JPH0482278A - Light emitting diode - Google Patents

Abstract

PURPOSE:To form an edge light-emitting LED element whose light-emitting output change by a temperature is small by a method wherein an active layer is formed at an acute angle to an electrode and light is taken out directly in a direction which is nearly parallel to the electrode. CONSTITUTION:An n-type GaAs buffer layer 2 is grown heteroepitaxially on a low-resistance n-type Si substrate 1 by a molecular beam epitaxy method or an organometallic vapor growth method. In addition, an n-type GaAlAs layer 3, a GaAs active layer 4 and a p-type GaAlAs layer 5 are epitaxially grown sequentially; after that, one part is etched and removed. After that, an ITO 6 as a transparent conductive substrate is formed by a sputtering operation. The substrate 1 and the ITO 6 are polished and tilted with reference to the active layer 4. Au electrodes 7 high in reflectivity are formed on the substrate 1 and the ITO 6 by a sputtering operation. Thereby, it is possible to form an edge light-emitting LED element whose light-emitting change by a temperature is small.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a substrate structure and configuration of a light emitting diode.

[Conventional technology]

Conventionally, an edge-emitting type LED that takes out light in a direction horizontal to a p-n junction is disclosed, for example, in Kogaku (Toshio Uji; Kogaku, Vol. 15, No. 2, 1986. p. 53-54). Figure 2 shows the edge-emitting type L disclosed in this document.
This is the element structure of the ED.

In FIG. 2, n-type InP is placed on an n-type InP substrate 21.
Layer 22. GaInAsP active layer 23. p-type InP layer 24
．． n-type GaInAsP layer 25. N-type InP layers 26 are successively formed. A region 27 indicated by a broken line is a diffusion region. 28 is a p-type contact, and 29 is an n-type contact.

The depression in the center of 28 is for concentrating the current injected into the junction of 22, 23, and 24. n-type In
P layer 22. The p-type InP layer 24 has a lower refractive index than the GaInAsP active layer 23, and has a lower refractive index than the GaInAsP active layer 23.
The light emitted by the sP active layer 23 is confined in the GaInAsP active layer 23, propagates, and is emitted in a direction parallel to the pn junction.

[Problem to be solved by the invention]

As shown in Figure 2, in the conventional edge-emitting LED,
Compared to surface-emitting LEDs that emit light in a direction perpendicular to the pn junction, the temperature change in output is about 1 to 10 times larger. In particular, when the current injection region is narrowed or a buried structure is used,
There are problems with stability when used in optical transmission technology, as it may oscillate at low temperatures or its output may fluctuate by a factor of ten or more over the operating temperature range. As mentioned above, the light emitted in the active layer 23 in FIG.
type InP layer 22. Confined by the p-type InP layer 24, the active layer 23 also serves as a waveguide layer. The output of this waveguide layer is wavelength dependent. When the temperature changes and the forbidden band width of the active layer 2 changes, the wavelength of maximum gain changes. Therefore, the temperature change in the output becomes large. Therefore, in order to solve the problems of the prior art and provide edge-emitting LED elements that operate stably in various temperature environments, it is necessary to take measures to suppress output changes due to temperature changes.

When forming a light-emitting region by stacking semiconductors with different thermal expansion coefficients and lattice constants on a semiconductor substrate, there is a problem that the crystallinity of the stacked semiconductors decreases, and heat is required to obtain high-quality light-emitting elements. It is necessary to alleviate differences in expansion coefficients and lattice constants.

When producing an edge-emitting LED element, the light emitted by the active layer is absorbed along its traveling path, resulting in a decrease in light utilization efficiency as a light-emitting element. Therefore, it is necessary to take measures to suppress absorption along the path of light. Furthermore, in order to further improve the light utilization efficiency, it is necessary to limit the direction in which the light is output.

[Means to solve the problem]

In order to provide an edge-emitting LED element with a small change in luminous output due to temperature, the active layer is not used as a waveguide layer that confines the emitted light inside, but the light emitted by the active layer is taken out and propagated outside.

In the present invention, in a light emitting diode having a laminated structure including an active layer and an electrode for applying an electric field to this laminated structure,
The layered structure including the active layer forms an acute angle to the electrodes, and the objective is achieved by directly extracting light in a direction that is not blocked by the electrodes.

When semiconductors having different thermal expansion coefficients and lattice constants are stacked on a semiconductor substrate, the stacked semiconductor layers are made to have good crystallinity by sandwiching an appropriate buffer layer therebetween.

As a measure to suppress the absorption of light emitted from the active layer in the traveling path, a conductive material that is transparent to the light emitted from the active layer is interposed between the laminated structure including the active layer and the electrode. Improve the light utilization efficiency as an element. Furthermore, by making the electrodes have high reflectance, the light utilization efficiency is further improved.

[Effect]

an active layer, a first conductivity type semiconductor layer adjacent to the active layer on the substrate side and having a larger forbidden band width than the active layer; and a first conductivity type semiconductor layer adjacent to the active layer and on the opposite side to the substrate and having a larger forbidden band width than the active layer. In a light emitting diode, the active layer forms an acute angle to the electrode and directly extends in a direction substantially parallel to the electrode in a light emitting diode having a laminated structure including a biconducting semiconductor layer and an electrode for applying an electric field to the laminated structure. By extracting light, it is possible to form an edge-emitting LED element whose light emission output changes little due to temperature. In addition, in this edge-emitting LED, the electrode is A u
+ A Q t By using a metal such as Cu, an edge-emitting LED element with high light utilization efficiency can be formed. Furthermore, in this edge-emitting LED, by interposing a buffer layer between the first conductivity type semiconductor substrate and the laminated structure including the active layer, an edge-emitting LED element having a laminated structure with good crystallinity can be formed. . This edge-emitting LE
In D, by interposing a conductive material transparent to light emitted by the active layer between the laminated structure including the active layer and the electrode, an edge-emitting LED element with high light utilization efficiency can be formed.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. An n-type GaAs buffer layer 2 is heteroepitaxially grown on a low-resistance n-type Si substrate 1 by molecular beam epitaxy (MBE) or metal organic chemical vapor deposition (MOCVD), and an n-type GaAlAs layer 3, G a A
After a predetermined crystal growth is performed to epitaxially grow the s active layer 4tP type GaAQAs layer 5 one after another, parts of layers 2 to 5 are removed by etching. Thereafter, IrO6 is formed as a transparent conductive material by sputtering.

As shown in the figure, the Si substrate 1 and IrO 6 are polished to be oblique to the active layer 4. Si substrate 1 and IrO
2, an Au electrode 7 with high reflectance is formed by sputtering.

〔Effect of the invention〕

Since the present invention is configured as described above, it produces the effects described below.

In the present invention, an active layer, a first conductivity type semiconductor layer adjacent to the active layer having a larger forbidden band width than the active layer, and a second conductive type semiconductor layer adjacent to the active layer having a larger forbidden band width than the active layer are provided. In a light-emitting diode having a laminated structure including a laminated structure and an electrode for applying an electric field to this laminated structure, the active layer forms an acute angle to the electrode and directs light in a direction substantially parallel to the electrode, It is possible to form an edge-emitting LED element whose light emission output changes little due to temperature.

Further, in the present invention, in this edge-emitting LED, a buffer layer is interposed between the first conductivity type semiconductor substrate and the laminated structure including the active layer, thereby forming an edge-emitting LED element having a laminated structure with good crystallinity. be able to.

Further, in the present invention, in this edge-emitting LED, an edge-emitting LED element with high light utilization efficiency can be formed by interposing a transparent conductive material between the laminated structure including the active layer and the electrode.

In the present invention, the electrodes in this edge-emitting LED are made of Au,
By using a metal such as AQ or Cu, an edge-emitting LED element with high light utilization efficiency can be formed.

[Brief explanation of drawings]

FIG. 1 is a perspective view of an embodiment of an edge-emitting LED according to the present invention, and FIG. 2 is a perspective view of a conventional edge-emitting LED.

Claims (1)

[Claims] 1. A first conductive layer formed on a first conductive type semiconductor substrate, adjacent to at least one active layer, on the first conductive type semiconductor substrate side, and having a larger forbidden band width than the active layer. a second conductivity type semiconductor layer adjacent to the active layer and on the opposite side of the first conductivity type semiconductor substrate and having the forbidden band width larger than the active layer; In the light emitting diode, the active layer is arranged at an acute angle to the electrode and is substantially parallel to the electrode, and the electrode is substantially parallel to the upper surface of the conductive semiconductor substrate and applies an electric field to the laminated structure. A light emitting diode characterized by being configured so that light can be extracted in a specific direction. 2. an n-type semiconductor layer formed on an n-type semiconductor substrate, adjacent to at least one active layer and having a larger forbidden band width than the active layer; a stacked structure including a p-type semiconductor layer on the opposite side to the active layer and having the forbidden band width larger than the active layer; and an electrode that is substantially parallel to the upper surface of the n-type semiconductor substrate and applies an electric field to the stacked structure. A light emitting diode comprising: the active layer forming an acute angle with respect to the electrode and extracting light in a direction substantially parallel to the electrode. 3. A p-type semiconductor layer formed on a p-type semiconductor substrate, adjacent to at least one active layer and on the side of the p-type semiconductor substrate, and having a larger forbidden band width than the active layer; a laminated structure including an n-type semiconductor layer on the opposite side of the type semiconductor substrate and having a larger forbidden band width than the active layer;
and an electrode that is substantially parallel to the upper surface of the p-type semiconductor substrate and applies an electric field to the layered structure, wherein the active layer forms an acute angle with the electrode and emits light in a direction substantially parallel to the electrode. A light emitting diode characterized by taking out. 4. In claim 2, the n-type semiconductor substrate is an n-type Si substrate, the active layer is a GaAs layer, the n-type semiconductor layer is an n-GaAlAs layer, and the p-type semiconductor layer is a p-type semiconductor layer.
- Light emitting diodes each using a GaAlAs layer. 5. In claim 3, the p-type semiconductor substrate is a p-type Si substrate, the active layer is a GaAs layer, the p-type semiconductor layer is a p-GaAlAs layer, and the n-type semiconductor layer is an n-type semiconductor layer.
- Light emitting diodes each using a GaAlAs layer. 6. In claim 1, the first conductivity type semiconductor substrate;
a first conductivity type semiconductor layer adjacent to at least one active layer and on the first conductivity type semiconductor substrate side and having a larger forbidden band width than the active layer; adjacent to the active layer and opposite to the first conductivity type semiconductor substrate; A light emitting diode in which a buffer layer is provided between a laminated structure including a second conductivity type semiconductor layer located on the side and having a larger forbidden band width than the active layer. 7. In claim 1, a first conductivity type semiconductor layer adjacent to at least one active layer and on the side of the first conductivity type semiconductor substrate and having a larger forbidden band width than the active layer; A laminated structure including a second conductivity type semiconductor layer opposite to the first conductivity type semiconductor substrate and having the forbidden band width larger than the active layer, and a layer transparent to the light emitted by the active layer between the electrode and the second conductivity type semiconductor layer. A light emitting diode with a conductive substance interposed in it. 8. The light emitting diode according to claim 7, wherein ITO is used as the conductive material that is transparent to the light emitted by the active layer. 9. The light emitting diode according to claim 1, wherein the electrode is formed using a metal such as Au, Al, or Cu.