JPS63257281A - Edge emission type light emitting diode - Google Patents

Abstract

PURPOSE:To prevent the laser oscillation by changing the current density inside a device by a method wherein an LED of the edge light emitting type is constituted to have a current constriction structure where the width of a groove is changed continuously inside the device. CONSTITUTION:An n-type InP current block layer 2 is grown on a p-type InP substrate 1. Then, a groove 8 is made on the n-type InP block layer 2 by a selective etching method by making use of a photoresist film as a mask in such a way that the groove is 9 mum in width on the light emitting side and 0 in width on the reflection side. A p-type InP clad layer 3, a p-type InGaAsP active layer 4, an n-type InP clad layer 5 and an n-type InGaAsP cap layer 6 are grown in succession on the layer. The current density to be injected into the active layer is smaller than the current density inside the groove 8 because an electric current is spread in the transverse direction in the p-type InP clad layer 3; in addition, because the width of the groove 8 becomes gradually narrow from the light emitting side toward the reflection side, the current density to be injected into the active layer in a region near the reflection side becomes considerably small as compared with another region near the light emitting side.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to the structure of an edge-emitting type light emitting diode.

[Conventional technology]

Edge-emitting light emitting diodes (LEDs) are considered promising as light sources for communication because they have a characteristic of high coupling efficiency with optical fibers. Conventionally, this type of LED has a current blocking layer provided inside the crystal.
D is known, but this is a p-type I as shown in Figure 2.
n-type In having a conductivity type opposite to that of the substrate is formed on the nP substrate 1.
After forming the P current blocking layer 2, at least the substrate 1 is
A groove 7 of a constant width and a depth of 5 and an n-type InGaAsP cap layer 6 were formed. Therefore, the current injected from the substrate passes through the groove and is injected into the active layer, but since the groove width is the same over the entire device length, the current density of the current injected into the active layer is proportional to the device length. There was no difference in direction.

[Problem that the invention seeks to solve]

In the conventional edge-emitting LED described above, the groove structure for current confinement is applied over the entire surface from the light-emitting surface to the reflective surface, so when the injected current becomes high, the cleavage plane on the element end-face becomes a resonator, causing laser oscillation. Due to the generation of the triggering threshold, the linearity of the current-light output characteristics is lost. Furthermore, the change in the current light output characteristic curve due to temperature becomes significant, so the LED
The conventional drive circuit had the disadvantage that it was difficult to control the output.

[Means for solving problems]

The present invention changes the current injection density within the device by continuously narrowing the groove width of the vortex part for current confinement from the light emitting surface toward the reflective surface, so that the gain is large on the light emitting surface side and the gain is large on the reflective surface side. An edge-emitting LED that exhibits good LED characteristics even at high current densities due to its structure that increases loss.
It provides:

〔Example〕

Next, an embodiment of the present invention in which InP-InGaAsP is used as a semiconductor layer will be described with reference to the drawings. FIGS. 1A', 1B, and 1C are perspective views showing the manufacturing process of each main part of a device according to a first embodiment of the present invention. First, as shown in FIG. 1(A), an n-type InP current blocking layer 2 is grown on a p-type InP substrate 1. Next, as shown in FIG. 1(B), using a photoresist film as a mask, selective etching is performed on the n-type InP block layer 2 to form grooves with a groove width of 9 μm on the light emitting side and a groove width O on the reflective side. form 8. On top of that, as shown in FIG. 1(C), p
InP type cladding layer 3, P type InGaAsP active layer 4,
An n-type InP cladding layer 5 and an n-type InGaAsP cap layer 6 are successively grown. Then, electrodes are provided on both sides to complete the LED. The element length is approximately 300 μm.

When a voltage is applied to the electrodes of the LED manufactured in this way to cause a current to flow, the current passes through the groove 8 from the p-type InP substrate 1 to the p-type InP cladding layer 3, the p-type InGaAsP active layer 4, and the nGaAsP active layer 4. type InP cladding layer 5, n-type InGaAsP
It flows into the cap layer 6. Here, the current density injected into the active layer 4 is smaller than the current density in the groove because of the current structure in the p-type InP cladding N3, and the groove width is from the light emitting surface side to the reflective surface side. , gradually narrows, so the current density injected into the active layer in the region near the reflective surface side is considerably smaller than in the region near the light emitting surface side. As a result, in the region near the reflective surface side, the gain that causes laser oscillation is not reached<<, but on the contrary, it has the effect of hindering laser oscillation.

Next, specific effects will be explained based on data. Third
The figure shows the experimental results of the current-light output characteristics of the edge-emitting type LED of the present invention. In the conventional example shown by the broken line, laser oscillation occurred with an injection current of about 20 mA, and LED characteristics could not be obtained for an injection current of 20 mA or more. On the other hand, the edge-emitting type LED according to the present invention shown by the solid line does not cause laser oscillation and has a good L of up to 80 mA.
It showed ED characteristics.

Next, as a second example of the present invention, an LED was manufactured in which a groove with a groove width of 9 μm on the light emitting surface and a groove width of 3 μm on the reflective surface was formed on the n-type InP current block N2.

FIG. 4 is a graph showing the results of investigating the failure rate due to laser oscillation with respect to an injection current of 30 mA. The vertical axis shows the defect rate due to laser oscillation, and the horizontal axis shows the ratio of the groove width on the reflective surface to the groove width on the light emitting surface.
This is the case of 1 on the horizontal axis, where the defective rate was 50%. The LED of the second embodiment according to the present invention has a defective rate of 12% when the horizontal axis is 3/9, and the LED of the first embodiment has a horizontal axis of 0.
In this case, the defect rate was 5%. In the second example, when the current-light output characteristics were examined, the same effects as in the first example were obtained.

〔Effect of the invention〕

As explained above, the present invention prevents laser oscillation by changing the current density within the element by having a current confinement structure in which the groove width changes continuously within the element in an edge-emitting LED. This has the effect of making it possible to obtain high-output, high-quality LEDs at a high yield.

[Brief explanation of drawings]

FIGS. 1(A) to (C) are perspective views showing the manufacturing process of an edge-emitting type LED in the first embodiment of the present invention, and FIG.
) to (C) are perspective views showing the manufacturing process of the conventional edge-emitting type LED, FIG. 3 is a diagram showing the current-light output characteristics of the edge-emitting type LED of the present invention, and FIG. 4 is a diagram showing the edge-emitting type LED of the present invention. Luminous LED
FIG. 3 is a comparison diagram between the defective rate due to laser oscillation and the conventional case. 1...p-type InP substrate, 2...n-type InP block layer, 'l...pffiInP cladding layer, 4 ・p-type I
nGaAsP active layer, 5... n-type InP cladding layer,
6... n-type InGaAsP cap layer, 7, 8...
groove. 3V off

Claims (1)

[Claims] In an edge-emitting light emitting diode in which a striped groove reaching the substrate is formed in a current blocking layer formed on a semiconductor substrate to narrow the injection current, the width of the groove is continuous from the light emitting surface side to the reflective surface side. An edge-emitting type light-emitting diode characterized in that a current injection area is restricted by narrowing the area to .