JPH077848B2 - Edge emitting type light emitting diode - Google Patents

Description

The present invention relates to a structure of an edge emitting light emitting diode.

[Conventional technology]

The edge emitting type light emitting diode (LED) is regarded as a promising light source for communication because it has a feature of high coupling efficiency with an optical fiber. Traditionally, this kind of
As an LED, an LED in which a current block layer is provided inside a crystal is known. This is a p-type InP substrate 1 as shown in FIG.
After forming an n-type InP current blocking layer 2 having a conductivity type opposite to that of the substrate, a groove 7 having a constant width with a depth reaching at least the substrate 1 is provided, and thereafter, the substrate is provided inside and outside the groove. P-type InP clad layer 3 of the same conductivity type as 1 and p-type InGaA
The sP active layer 4, the n-type InP clad layer 5, and the n-type InGaAsP cap layer 6 were formed. Therefore, the current injected from the substrate is injected into the active layer through the groove. However, since the groove width is the same across the entire element length, the current density of the current injected into the active layer is in the element length direction. So there was no difference.

[Problems to be solved by the invention]

In the above-mentioned conventional edge emitting LED, the groove structure for current confinement is provided on the entire surface from the light emitting surface to the reflecting surface, so when the injected current becomes high, the cleaved surface of the element end surface becomes a resonator to cause laser oscillation. Due to the raising threshold, the line formation of the current-light output characteristic is lost. Furthermore, since the current-light output characteristic curve changes significantly with temperature, the LED driving circuit has a drawback that it is difficult to control the output.

[Means for solving problems]

The present invention changes the current injection density in the element by continuously narrowing the groove width of the groove portion for current constriction from the light emitting surface to the reflecting surface, resulting in a large gain on the light emitting surface side and a loss on the reflecting surface side. By providing a structure having a large LED, an edge emitting LED that exhibits excellent LED characteristics even at high current densities is provided.

〔Example〕

Next, the present invention will be described with reference to the drawings with respect to an embodiment in which InP-InGaAsP is used as a semiconductor layer. FIGS. 1 (A), (B), and (C) are perspective views showing the manufacturing process of each main part of the device of the first embodiment of the present invention. First, the first
An n-type InP current blocking layer 2 is grown on a p-type InP substrate 1 as shown in FIG. Then, as shown in FIG. 1B, a groove 8 of the same depth having a groove width of 9 μm on the light emitting side surface and a groove width of 0 on the reflective side surface is selectively etched by using the photoresist film as a mask on the n-type InP block layer 2. To form. On top of that, as shown in FIG. 1 (C), the p-type In cladding layer 3, p
-Type InGaAsP active layer 4, n-type InP clad layer 5, and n-type
The InGaAsP cap layer 6 is continuously grown. The LED is completed by providing electrodes on both sides. The element length is about 300 μm.

When a voltage is applied to the electrode of the LED thus manufactured and a current is caused to flow, the current passes through the groove 8 from the p-type InP substrate 1, the p-type InP clad layer 3, the p-type InGaAsP active layer 4, and the n-type. InP
It flows to the clad layer 5 and the n-type InGaAsP cap layer 6.
The current density injected into the active layer 4 is smaller than the current density in the groove due to the lateral spread of the current in the p-type InP clad layer 3, and the groove width is directed from the light emitting surface side to the reflective surface side. Since it is gradually narrowed, the current density injected into the active layer in the region near the reflecting surface side is considerably smaller than that in the region near the light emitting surface side. As a result, in the region near the reflecting surface side, it is difficult to reach the gain that causes laser oscillation, and on the contrary, the effect of hindering laser oscillation is brought about.

Next, specific effects will be described based on data. Third
The figure shows the experimental results of the current-light output characteristics of the edge emitting 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 the LED characteristics could not be obtained for an injection current of 20 mA or more. On the other hand, the edge emitting LED according to the present invention shown by the solid line did not cause laser oscillation and showed good LED characteristics up to 80 mA.

Next, as a second embodiment of the present invention, a groove width of 9 μm on the light emitting surface and a groove width of 3 on the reflecting surface are formed on the n-type InP current blocking layer 2.
An LED with a groove of μm was manufactured.

FIG. 4 is a graph showing the results of investigating the defect rate due to laser oscillation with respect to an injection current of 30 mA. The vertical axis represents the defect rate due to laser oscillation, and the horizontal axis represents the ratio of the groove width of the reflecting surface to the groove width of the light emitting surface. Conventional LED has 1 horizontal axis
And the defective rate was 50%. Second according to the present invention
The LED of Example 1 had a defect rate of 12% when the horizontal axis was 3/9, and the LED of the first example had a defect rate of 5% when the horizontal axis was 0. When the current-light output characteristics were examined in the second example, the same effect as in the first example was obtained.

〔The invention's effect〕

As described above, the present invention prevents the laser oscillation by changing the current density in the element by having the current confinement structure in which the groove width is continuously changed in the element in the edge emitting LED. There is an effect that a good LED with high output can be obtained with high yield.

[Brief description of drawings]

1 (A) to 1 (C) are perspective views showing a manufacturing process of an edge emitting LED according to the first embodiment of the present invention, and FIG. 2 (A).
(C) is a perspective view showing a manufacturing process of a conventional edge emitting LED, FIG. 3 is a diagram showing current-light output characteristics of the edge emitting LED of the present invention, and FIG. 4 is an edge emitting type of the present invention. FIG. 8 is a comparison diagram of a defect rate due to laser oscillation of an LED and a conventional case. 1 ... p-type InP substrate, 2 ... n-type InP block layer, 3 ...
p-type InP clad layer, 4 ... p-type InGaAsP active layer, 5 ...
n-type InP clad layer, 6 ... n-type InGaAsP cap layer, 7,
8 …… Groove.

Claims (1)

[Claims] 1. An edge emitting light emitting diode in which a stripe-shaped groove reaching the substrate is formed in a current blocking layer formed on a semiconductor substrate to confine the injected current, and the groove width of the groove is reflected from the light emitting surface side. An edge emitting light emitting diode characterized in that a current injection region is limited by continuously narrowing it to the surface side.