JPS6386579A - Light emitting diode - Google Patents

Abstract

PURPOSE:To make optical output itself large, and increase the incident power into an optical fiber, by constituting the active layer and the inverter conductivity type semiconductor layer of a p-type or an n-type semiconductor substrate in a burying structure, making the length of the active layer in the direction of stripe long, and taking out, from end surfaces, the light whose wavelength produces optical gain. CONSTITUTION:After an n-InP buffer layer 2, an InGaAsP active layer 3, a p-InP current confined layer 4 and a p-InGaAsP cap layer 5 are grown on the surface of an n-InP substrate 1, a p-InP layer 6, an n-InP layer 7 and a p-InP layer 8 are grown in order on both sides of a stripe type mesa part. An electrode 10 is arranged on an SiO2 insulative layer 9, and a contact is formed only in the mesa stripe part. When a current is made to flow between the electrodes 10 and 11, the current is injected from the mesa stripe, and light is emitted from the active layer 3, which is effectively taken out from end surfaces 21 and 22 whose reflectivity are made small. When the active layer is excited, a bandwidth having gain in the long wavelength side of spontaneous emission light is produced. By making the length of the active layer 3 long, the light in this band is amplified, so that large output light whose half-width of emission spectrum is narrow is emitted from the end surfaces 21 and 22.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a light emitting diode suitable for optical fiber communication.

[Conventional technology]

In order to use a light emitting diode as a light source in optical fiber communication, it is necessary to have a structure that allows output light to enter the optical fiber efficiently. Conventionally, optical fibers for optical fiber communications can be broadly classified into:
Surface emitting type light emitting diodes and edge emitting type light emitting diodes are known.

[Problems to be solved by the invention]

However, surface-emitting light emitting diodes have a light output of about 1~
Although it is as large as 2 mW, both the radiation angle and the light emitting area are relatively large, so there is a problem that the output that enters the optical fiber is small. For example, the input power to a graded index optical fiber with an outer diameter of 125 μm and a core diameter of 50 μm is 80 μW.On the other hand, an edge-emitting type light emitting diode has a higher light emitting output than a surface-emitting type light emitting diode. It is small at about 0.3mW. This is because in an edge-emitting type light emitting diode, the short wavelength component of light that passes through the active layer that goes almost perpendicular to the edge is absorbed, so the light emitted deeper than the edge from which the light is taken out has a negative effect on the optical output. This is because the curvature does not contribute, and only the light emission near the end surface mainly contributes. in spite of,
Since the radiation angle is small and the light emitting area is small, for example, the incident power to the same graded index optical fiber as above is about 80 μW, and the incident power to the optical fiber is about the same. This invention takes advantage of the edge-emitting type light-emitting diode's small radiation angle and small light-emitting area, and improves the light-emitting output itself to increase the incident power to the optical fiber. The purpose is to provide

[Means to solve the problem]

The light emitting diode of the present invention has an active layer and an opposite conductivity type semiconductor layer sequentially formed on one surface of a p-type or n-type semiconductor substrate in a mesa stripe-like buried structure, and the length of the active layer in the stripe direction is It is characterized in that it is made long so that light of a wavelength at which an optical gain occurs is extracted from the end face.

[For production]

When the active layer is excited, a band where gain occurs appears on the long wavelength side of spontaneously emitted light. Therefore, by lengthening the active layer, the amplification effect of light in that band can be strengthened. As a result, light with a narrow spectrum in this band is amplified, becomes a large output, and is emitted from the end face.

【Example】

1 to 3, on one surface of an n-1nP substrate 1, an n-1nP buffer layer 2, an InGaAsP active layer 3, a p-InP current confinement layer 4, a p-1nGa
After the AsP cap layer 5 is epitaxially grown in sequence, it is etched so that a striped mesa portion with a width of several μm remains. Next, p-1nP layers 6 are placed on both sides of this mesa part.
, an n-InP layer 7 and a ρ-1nP layer 8 are sequentially grown to fill this mesa portion. 5i further north of these
A 02 insulating layer 9 is provided, and striped windows are formed in this 5i02 insulating layer 9. Then, an electrode 10 is provided on this so that a contact is formed only in this window portion, that is, in the mezas I/live portion. Further, an electrode 11 is provided on the back surface of the n-InP substrate 1. The thickness of the active layer 3 is about 0.1 μm, and the length of the substrate 1 is set to several mtn, so that the length of the active layer 3 is made sufficiently long. A non-reflective coating with a reflectance of about 5% is applied to the end faces 21 and 22 on the light emitting side. When a current is passed between the electrodes 10 and 11, the current is injected from the mesus l~live having a width of several/-Z m, and light is emitted from the active layer 3 having the same width. This light is efficiently extracted to the outside through the end surfaces 21 and 22 whose reflectance is lowered. In this case, the light output to the outside has a long activity increase in the light emission direction, so components in a specific wavelength band are amplified, resulting in a large output. That is, generally, as shown in FIGS. 4A and 4B, when the active layer is in an excited state, a band with gain is generated on the long wavelength side of spontaneously emitted light. Therefore, by making the active layer 3 longer as described above, the light in this band is amplified, and output light with a small half-value width of the emission spectrum and a large output is emitted from the end faces 21 and 22. Therefore, while taking advantage of the edge-emitting type light-emitting diode's small radiation angle and small light-emitting area, it is possible to increase the output as much as that of a surface-emitting type light-emitting diode, thereby increasing the power incident on the optical fiber. can do. In addition, when it is sufficient to output light from one side without outputting light from both of the end faces 21 and 22, a reflective film may be provided on the other side. It is also possible to adopt a superlattice structure for the active layer.

【Effect of the invention】

According to the light emitting diode of the present invention, it is possible to emit light with a narrow spectrum and high output at a radiation angle smaller than that of a small area on the end face, so that the light incident power to the optical fiber coupled to the end face can be increased. can do.

[Brief explanation of the drawing]

FIG. 1 is a plan view of an embodiment of the present invention, FIG. 2 is a sectional view taken along line A-A in FIG.
FIGS. 4A and 4B are graphs showing characteristics of spontaneous emission light intensity and gain coefficient. 1... n-InP substrate, 2... buffer layer, 3...
・Active layer, 4... Current confinement layer, 5... Cap layer, 6... p-1nP layer, 7...-n-1nP layer, 8-
p-1nP layer, 9... Insulating layer, 10.11... Electrode, 21.22... End surface.

Claims (1)

[Claims] (1) An active layer and an opposite conductivity type semiconductor layer sequentially formed on one surface of a p-type or n-type semiconductor substrate are formed into a buried structure in the form of a mesa stripe, and the length of the active layer in the stripe direction is lengthened, A light emitting diode that extracts light at a wavelength that produces optical gain from its end face.