JPH02294081A - Light emitting element - Google Patents

Abstract

PURPOSE:To radiate a light containing two or more kinds of wavelengths vertically to a laminated surface by providing two or more active layers having different band gaps between clad layers. CONSTITUTION:Between clad layers 2, 5, two or more active layers having different band gaps are arranged. That is, on an N-type GaAs substrate 1, the following are epitaxially grown; an N-type GaAlAs clad layer 2, a first p-type GaAlAs active layer 3, a second P-type GaAlAs active layer 4, a P-type GaAlAs clad layer 5, and a P-type GaAs contact layer 6. When a current is made to flow between electrodes 7, 9, the respective lights of surface light emitting parts 3a, 4a of the first active layer 3 and the second active layer 4 enter an optical fiber 11; the light from the surface light emitting part 4a of the second active layer 4 passes the first active layer 3 whose band gap energy is large, and can be led out by the optical fiber 11. Thereby a light emitting element which can radiate vertially from the laminated surface, a light containing a plurality of wavelengths can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to light emitting elements such as light emitting diodes and semiconductor lasers, and particularly to light emitting elements having two or more types of emission wavelengths. [Prior Art] Conventionally, light emitting diodes and semiconductor lasers have been used for display purposes. communication,
Light-emitting elements are used in a wide range of fields such as measurement.
It has a single wavelength. On the other hand, if light with multiple wavelengths can be emitted, the applications of light-emitting diodes and semiconductor lasers can be expanded. For example, most materials that can transmit light have different light absorption coefficients and propagation speeds depending on the wavelength of the light. Therefore, by passing light through this substance, it is possible to measure the concentration and length of the substance. At that time, using light sources with different wavelengths,
By examining changes in two wavelengths, measurement accuracy can be greatly improved. Light-emitting diodes and semiconductor lasers are used as light sources for these measurements because they have high light output and are small and lightweight. However, these are single wavelength light sources. In order to obtain multiple wavelengths, it is possible to fabricate a light source by collecting two or more types of light emitting elements with different emission wavelengths. However, this method requires a large light source. Also, when using the light in a focused manner, this is inconvenient. For example, when light from a light emitting diode or semiconductor laser is inserted into an optical fiber and used for communication or measurement, coupling efficiency is important. To let light into the thin core,
If there is only one chip, this can be achieved using conventional technology. Therefore, if a single chip can generate light of multiple wavelengths, various uses can be considered.

As shown in JP-A-56-15094 and JP-A-5,618,483, two or more types of light-emitting elements having different emission wavelengths are formed by forming two or more types of active layers on a substrate and forming each active layer respectively. The cladding layer/first active layer/cladding layer/
It has been shown that the laminated ellipse of the second active layer/cladding layer can emit light of two or more wavelengths. [Problems to be Solved by the Invention] However, this light emitting device requires electrodes to be provided in the direction of lamination, and is of a so-called horizontal type in which light is emitted in the direction of the laminated surface, making it difficult to obtain high output and making it difficult to manufacture. There is a problem that performance and mass productivity are reduced.

An object of the present invention is to eliminate the drawbacks of the prior art described above and to provide a light emitting element that can emit light of a plurality of wavelengths perpendicularly from a laminated surface. [A Thousand Steps to Solve the Problems] In order to achieve the above object, the present invention provides a light emitting device in which an active layer is sandwiched between rat layers having a band gap energy larger than that of the active layer. It has two or more active layers with different band gaps. [Function] According to the above configuration, since two or more active layers with different band gaps are provided between the cladding layers, light with two or more wavelengths can be emitted perpendicularly to the laminated surface, which is different from the conventional Similar to the vertical type single wavelength light emitting device, it has good manufacturability and mass productivity, and can provide high output.

[Examples] Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. Figure 1 shows an example of a light-emitting diode as a light-emitting element. This light emitting diode is a surface emitting Burrus type #A structure. In the figure, 1 is an n-type GaAs substrate, and an n-type GaAJl'As cladding layer 2 is formed on the GaAs substrate 1.
, p-type GaAJAs first active layer 3, p-type GaAJ2As
A second active layer 4, a P-type GaAJ)As cladding layer 5, and a P-type GaAs contact layer 6 are sequentially grown epitaxially. An nll1ll electrode 7 is placed on the GaAs substrate 1 side, and a p-type A Sif2 insulating film 8 is provided on the GaAs contact layer 6, and a
Drill a hole of 0 μmφ and form a pfflt pole. In the center of the substrate 1, facing the p III electrode 9, a hole 10 is made by selective etching to reach the n-type GaAJAs cladding layer 2, and an optical fiber 11 is inserted into the hole 10 and fixed with, for example, epoxy resin. do. Now, here, the AJAs mixed crystal ratio of the first active layer 3 is 0.14, the film thickness is 1.0 μm, and the AJAs mixed crystal ratio of the second active layer 4 is 0.00.
5, and the film thickness was 0.2.tzm. The cladding layer 2 is A
JAs mixed crystal ratio 0.30, film thickness 50 μm, cladding layer 5
has an AJAs mixed crystal ratio of 0.3 and a film thickness of 5 μm. The contact layer 6 is made of GaAs and has a thickness of 5 μm. In order to manufacture this epitaxial wafer, a liquid phase epitaxial method is used, and Te is used as an n-type dopant and Zn is used as a p-type dopant.

Next, the operation of the above embodiment will be explained. When a current is passed between the electrodes 7.9, p-type Ga A AAs
First active layer 3 and p-type GaAf! The positions of the As second active layer 4 facing the p-side electrode 9 become surface emitting parts 3a, 4a, and each light enters the optical fiber 11. In this case, the light emitted from the surface emitting portion 4a''C' of the second active layer 4 can pass through the first active layer 3 having a large bandgap energy and be extracted to the optical fiber 11. In order to make the light emitting output of the second active layer 4 the same, the active layer carrier concentration should be made equal and the film thickness of the first active layer 3 should be made thinner than that of the second active layer by 0.5 μm. The emission wavelength of this light emitting diode is 88
0 nm, and 780 nm for the second active layer 4. The relative intensity of both light wavelengths depends on the forward current, but if the current is constant, the relative intensity can be kept constant.

In the above embodiment, two types of emission wavelengths were used, but the emission wavelength can be increased by increasing the number of active layers. Although the Buruss type is shown, the same effect can be applied to other types of light emitting diodes, such as edge-emitting types, if the number of active layers is increased. This method can also be applied to semiconductor lasers by increasing the number of active layers. In this case, laser light with two wavelengths, or laser light and light emitting diode light, can be used depending on the difference in threshold current. [Effects of the Invention] As is clear from the above explanation, the present invention exhibits the following excellent effects.

(1) When condensing and transmitting light into a fiber or a smile measurement sample, the optical system is simple because it is a single chip, and conventional vertical type technology can be used as is. (2) Since the two types of light emitting waves are emitted from one chip, the temperature is the same, and there is little change in relative intensity. (3) For pulse response experiments, the characteristics are consistent and there is no time delay since they are all on the same chip.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing one embodiment of the present invention. In the figure, 1 is an n-type GaAs substrate, 2 is an n-type GaAIAs cladding layer, and 3 is a p-type GaAj! As first active layer, 4 is ρ
type GaAjlAs second active layer, 5 is p-type GaAj! As
This is the cladding layer. Patent applicant Hitachi Cable Co., Ltd. Agent Patent attorney Nobuo Kinutani

Claims (1)

[Claims] 1. A light-emitting element in which an active layer is sandwiched between rat layers having a band gap energy larger than that of the active layer, characterized in that two or more active layers having different band gaps are provided between the cladding layers.