JPH01137679A - Semiconductor light emitting element - Google Patents

Abstract

PURPOSE:To enhance the luminous output of the title element by a method wherein light of strong intensity light emitted from the light emitting layer located directly under a surface electrode is reflected by a light reflection surface of a recessed and spherical shape, and the light is led out from a surface other than the part of the surface electrode. CONSTITUTION:Of the rear surface of a light emitting diode, a region symmetrical with respect to a light emitting layer located directly under the electrode part 6 formed on the surface is formed in a recessed and spherical surface 8. As a result, the light of strong intensity emitted from the light emitting layer 3 located directly under a surface electrode 6 is reflected by the above- mentioned surface 8, and is taken out from a part other than the surface electrode 6. Accordingly, luminous output can be enhanced.

Description

[Detailed description of the invention] Industrial applications The present invention relates to the structure of a light emitting diode.

Conventional technology Conventionally, this type of light emitting diode is shown in Fig. 2(a), (
b) It had a configuration of two cross-sections, a front electrode pattern and a back electrode pattern, as shown in (C). In FIG. 2(a), 1 is n-type Gal-xAQ xA s (x =
0.4), 2 is n-type Gal-xAe xA 5(x
-0,2>, 3 is p-type GaAs light emitting layer, 4 is p-type Ga
I-x A e x A s (x -0, 35),
5 is p-type Ga1-xAe, As (x=0.17), 6
is the A u/Be electrode, and 7 is the A u/G e electrode. In this conventional light emitting diode, p-type GaA
n-type Ga H-x installed below the s-emitting layer 3
A i! xAs 2 and xAs 1 are transparent to the emission wavelength (880 nm) of the present light emitting diode. If the semiconductor crystal placed below the light-emitting layer is transparent to the emission wavelength, the electrode 7 on the back surface is formed partially as shown in FIG. Light is extracted from the surface by reflection.

Problem to be Solved by the Invention When the electrode shape on the surface is as shown in FIG. 2(b), the current is
The flow generally spreads as shown in Figure 3(a), but the p-type G
al-xAl! Due to the spreading resistance of xA s 4 and 5, the current density in the light emitting layer is highest in the portion immediately below the surface electrode as shown in FIG. 3(b). p-type Ga (-, A
The thickness of exAs 4 and 5 is usually several μm, and the thinner these layers are, the stronger the tendency for current to concentrate on the light emitting layer directly under the surface electrode. Generally, the luminescence intensity is proportional to the current density, so the luminescence intensity in the luminescent layer is strongest immediately below the front electrode. However, if the back electrodes are uniformly distributed as shown in Figure 2 (C), The light emitted by the light-emitting layer directly below the front electrode and directed downward is absorbed by the back electrode, and much of the light reflected by the flat light-reflecting surface is blocked by the upper surface electrode and cannot be extracted. However, there was a problem in that the conventional light reflecting surface on the back side could not effectively extract the light from the portion where the luminous intensity was strong, which was disadvantageous in increasing the luminous output.

The present invention is intended to solve these problems, and aims to effectively extract the high-intensity light emitted from the light-emitting layer immediately below the surface electrode, thereby increasing the light-emitting output.

Means for Solving the Problem In order to solve this problem, the present invention provides a concave and spherical surface for the region directly below the electrode portion formed on the front surface of the back surface of the light emitting diode. The crystal plane is exposed.

Effect By making the part of the back surface directly below the front electrode into a concave and spherical surface, this part becomes a convex light-reflecting surface when viewed from inside the crystal, and the part directly under the front electrode with high emission intensity is reflected. Light can be extracted effectively.

Embodiment FIG. 1(a) is a cross-sectional view of a light emitting diode according to an embodiment of the present invention, FIG. 1(b) is a surface electrode shape, and FIG. 1(C) is a sectional view of a light emitting diode according to an embodiment of the present invention.
is the shape of the back electrode. In Figure 1(a), 1 is n
Type Ga+-xAex As (x=0.4), 2 is n-type Ga+-xAexAs (x=0.2), 3 is p-type GaA
s light-emitting layer, 4 is p-type Ga1-, AexAs (x=0.3
5), 5 is p-type Ga1-, A+2. As (x=0.1
7), 6 is the front side A u / Be electrode, 7 is the back side A
It is a u/Ge electrode. The basic configuration is the same as the conventional example shown in FIG. 2, but the shape of the back electrode and the shape of the back surface are different from the conventional example.

Such a light emitting diode will be explained with reference to each figure in FIG. 1, and will be manufactured as follows.

First, an n-type GaAs substrate (not shown) was grown by liquid phase epitaxial growth on an n-type GaAs substrate (not shown).
x=0.4) 1 as gQμm, n-type Ga1-, AexAs
(x-0,2)2 is 15 μm, p-type GaAs light emitting layer 3 is 1 u m r p-type Gap-xAexAs (x=0
．． 35) 4 is 2am, p-type Ga1-xAexAs (x
=0.17) 5 to 4 μm. Next, p-type Ga
1-, A e, As (x=0.17) A u on 5
/Be alloy is deposited, and an electrode 6 having a diameter of 120 μm is formed by photolithography. Then the n-type G
aAs substrate (not shown) with hydrogen peroxide: ammonia = 20
: Etched with a mixed solution of 1 to remove n-type Ga 1-xA
A u/G e alloy was deposited on one surface of exAs(x-0,4), and the photolithography method was used to deposit the A u/G e alloy as shown in Fig. 1 (C
) The electrode 7 has a shape with a diameter of 150 μm in the center.
form.

And an n-type with a diameter of 150 um (:, 211-xA
A spherical hole 8 having a depth of about 8 μm is formed in the center of the back surface of exA 5 (x-0, 4), 1 with a mixture of peroxide, arsenic, and phosphoric acid. This portion becomes a convex light-reflecting surface when viewed from inside the crystal.

If the back surface of the light-emitting layer, which is plane-symmetrical to the front electrode, is made concave and spherical, the light emitted from the light-emitting layer directly under the front electrode and directed downward will be reflected as shown by the arrow in Figure 1(a). As shown, when viewed from inside the crystal on the back side, the light is reflected diagonally upward by the convex, spherical reflecting surface, and is not blocked by the front electrode (
, can be removed from the surface. Comparing this with the conventional example and looking at its characteristics, the light emitting diode has a conventional structure in which electrodes with a diameter of 70 μm on the back side are formed at intervals of 106 μm as shown in Figure 2 (C). Output is 6 at 50mA
．． 4 mW, and the driving voltage at that time was 1.36 V, whereas the light emitting output of the light emitting diode according to the embodiment shown in the first figure was 7.2 mW at 50 mA, which is about 12% compared to the conventional light emitting diode. Improved light output. In addition, the area ratio of the back electrode in one embodiment of the present invention is 34%, and the driving voltage of the light emitting diode is 1.36 at 50 mA.
V and the conventional example. From this, the proportion of the light reflecting surface should be the same between the embodiment of the present invention and the conventional example, but the light emitting output of the light emitting diode according to the embodiment of the present invention is about 12% higher (the light emitting diode according to the embodiment of the present invention has a It can be seen that the reflected light is effectively extracted.

Effects of the Invention As described above, according to the present invention, the high-intensity light emitted from the light-emitting layer directly under the front electrode is reflected by the light-reflecting surface, which is convex and spherical when viewed from inside the crystal formed on the back surface. The light can be taken out from the surface other than the surface electrode portion, and the light emission output can be increased.

[Brief explanation of the drawing]

FIGS. 1(a), (b), and (C) are cross-sectional views of a light emitting diode according to an embodiment of the present invention; FIGS.
(C) is a cross-sectional view of a conventional light emitting diode and a surface electrode pattern. The back electrode pattern diagrams, FIGS. 3(a) and 3(b), are typical characteristic diagrams showing the current path distribution seen in cross section and the current density in the light emitting layer. 1--...-n type Ga1-, AexAs (x=0.4
), 2--- ・-n-type Ga+-xAexAs (x
=0.2), 3-p-type GaAs light emitting layer, 4--p-type GaI-xAexAs (x=0.35), 5-...-p
Type Ga■-xAexAs (x=0.17), 6-Surface A u / B e electrode, 7... Back surface A u
/ G e electrode. Name of agent: Patent attorney Toshio Nakao and one other person Figure 1 Figure 3 (b)

Claims (1)

[Claims] A concave, spherical surface is provided on the back surface of the crystal of a surface-emitting type light-emitting diode, in a region that is symmetrical to the light-emitting layer with respect to the electrode portion formed on the surface, or in a region that includes the same portion. Characteristic semiconductor light emitting device.