JPH0786636A - Light emitting diode device - Google Patents

Abstract

PURPOSE:To obtain luminous output with efficiency by forming on a second cladding layer a current constricting layer of a higher refractive index than that of the second cladding layer, and forming electrodes on the underside of the substrate and on the periphery of the luminous screen. CONSTITUTION:A first cladding layer 22, an active layer 23, and a second cladding layer 24, are formed on a substrate 21 in this order. Silicon nitride 27 is formed on the entire surface thereof, and is selectively removed except for its central portion. The second cladding layer 24 is etched halfway using the silicon nitride 27 left in the center as an etching mask. A current constricting layer 28 of a higher refractive index than that of the second cladding layer 24, is formed thereon; however, no current constricting layer 28 is formed on the silicon nitride 27. The silicon nitride 27 is removed by etching, and then a contact layer 29 is formed. Finally, an electrode 26 is formed on the periphery of the contact layer 29 by vapor deposition to make the central portion of the luminous screen a luminous window 30, and further an electrode 25 is also formed on the underside of the substrate 21 by vapor deposition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting diode device, and more particularly to a surface emitting light emitting diode device having a double hetero structure suitable for use in spatial optical communication.

[0002]

2. Description of the Related Art FIG. 4 is a block diagram of a conventional surface emitting light emitting diode device having a double hetero structure. The light emitting diode device shown in FIG.
Type Al _0.3 Ga _0.7 As first cladding layer 2, n-type G
The active layer 3 of aAs and the second cladding layer 4 of p-type Al _0.3 Ga _0.7 As are sequentially laminated. Then, an n-type electrode 5 is provided on the back surface of the substrate 1, and is installed on the stem 8 via a conductive resin 7.

A p-type electrode 6 is provided on the second cladding layer 4 and is connected to the lead 10 by a gold wire 9. In such a light emitting diode device, the electrodes 5, 6 are
When a current is applied between them, the active layer 3 emits light, so that the light is emitted from the upper surface of the second cladding layer 4 to form a surface-emitting light emitting diode device.

[0004]

In the conventional light emitting diode device, the p-type electrode 6 is formed in the plane from which the light is output, and the p-type electrode 6 and the gold wire 9 are shaded by the output light. However, there is a problem in that the light emission output is reduced and the shape of the output light is not uniform because the light is absorbed or the output light is absorbed.

Therefore, the present invention has an object to provide a light emitting diode device which can obtain a highly efficient light emission output by reducing the light emission output surface for actual light emission and forming the electrodes outside the light emission output surface. And

[0006]

As means for achieving the above object, at least a first clad layer, an active layer, and a second clad layer having different conductivity types are provided on a substrate.
In the light emitting diode device having a double hetero structure in which the second cladding layer and the second cladding layer are formed in this order, a current confinement layer having a higher refractive index than that of the second cladding layer is provided in the second cladding layer, and And a light emitting diode device characterized in that an electrode is formed in the peripheral portion of the light emitting surface, or at least a first clad layer, an active layer, and a second clad layer having different conductivity types on the substrate. In a light emitting diode device having a double hetero structure in which a clad layer is formed in this order, a current constriction layer is provided on the second clad layer, an electrode is formed on the back surface of the substrate, and the current is output from the active layer. It is an object of the present invention to provide a light emitting diode device characterized in that an electrode is formed on a light emitting surface outside a region where light has a critical angle on the light emitting surface.

[0007]

As shown in FIG. 3, the light traveling from one medium A toward another medium B has a critical angle expressed by the following equation, where the refractive indices of the respective media A and B are a and b. When it reaches the boundary surface between the media A and B at an angle larger than θ, it is reflected at the boundary surface and does not travel into the medium B. θ = sin ^-1 (b / a)

Therefore, if θ ₁ <θ <θ ₂ ,
_{Since 1} reaches the boundary surface at the angle θ _1, it travels into the medium B, but since light ₂ reaches the boundary surface at the angle θ ₂ , it is reflected into the medium A.

From this, the light emitted from the light emitting surface of the light emitting diode device to the outside is only the light that has reached the light emitting surface at an angle smaller than the critical angle θ of the light emitted in the light emitting region. Will be output to.

If a current confinement layer is formed in the light emitting diode device to limit the current flow path, the light emitting portion of the light emitting region can be made smaller. When the current confinement layer has a high refractive index, the light emitted from the light emitting region toward the current confinement layer is reflected, so that the light output from the light emitting surface to the outside is between the current confinement layers. Only the light that reaches through to the light emitting surface is reached, and among the light emitting surface of the light emitting diode device,
The part that actually emits light becomes smaller. Therefore, if the electrode is provided on a portion of the light emitting surface other than the light emitting portion, the electrode does not become a shadow of the light emission output.

Further, the critical angle θ of the light output between the current confinement layers on the light emitting surface is calculated, and the light emitting surface within this angle θ is used as a window portion, and an electrode is provided at a portion other than this window portion. By providing the electrodes, it is possible to prevent the electrodes from shadowing the light emission output.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the light emitting diode device of the present invention will be described with reference to the drawings. Normally, a light emitting diode device is formed by forming a large number of light emitting diode devices having the same structure on one wafer and then separating them one by one. However, in the following embodiments, only one element will be taken up. The structure and manufacturing method will be described.

FIGS. 1A to 1E are process drawings showing a method of manufacturing an embodiment of a light emitting diode device of the present invention.
First, as shown in FIG.
The first cladding layer 22 of n-type Al _0.3 Ga _0.7 As is 20 μm, the active layer 23 of n-type GaAs is 1 μm, and the second cladding layer 24 of p-type Al _0.3 Ga _0.7 As is 20 μm by MOCVD. Are sequentially laminated with the thickness of. Then, the silicon nitride 27 is deposited over the entire surface by the CVD method to 2000.
It is formed to a thickness of about A (angstrom), and the other part is selectively removed using an HF aqueous solution, leaving a diameter of about 150 μm at the central part.

Next, as shown in FIG. 2B, the second cladding layer 24 is formed by using a phosphoric acid-based etching solution with the silicon nitride 27 remaining in the central portion as an etching mask.
The etching is performed halfway (in this embodiment, the depth is 10 μm). Then, as shown in FIG. (C), n-type Al _0.8
A Ga _0.2 As current confinement layer 28 is formed to a thickness of 10 μm by MO.
Stack using the CVD method. At this time, silicon nitride 2
No n-type Al _0.8 Ga _0.2 As is laminated on the surface of No. 7, and the surface is almost flat. Further, after removing the silicon nitride 27 by etching, as shown in FIG.
_{A 0.3} Ga _0.7 As contact layer 29 is laminated to a thickness of 5 μm by MOCVD.

Finally, a p-type AuBe / Au electrode 26 is vapor-deposited on the outer peripheral portion of the contact layer 29 to form a light-emitting window 30 at the center of the light-emitting surface, and the n-type GaAs substrate 21.
The light emitting diode device of the present invention can be manufactured by depositing the n-type AuGeNi / Au electrode 25 on the back surface of the. In the light-emitting diode device manufactured in this manner, when a current is passed between the electrodes 25 and 26, the current confinement layer 28 has a conductivity type different from that of the second cladding layer 24, so that no current flows, and the current is Since the current flows through between the current confinement layers 28, only the substantially central portion of the active layer 23 becomes the light emitting region a. Since the refractive index of the current confinement layer 28 is higher than that of the second cladding layer 24, of the light emitted from the light emitting region a, the light emitted to the current confinement layer 28 is
The light is reflected by the current confinement layer 28, passes between the current confinement layers 28, and reaches the light emitting surface together with other light. Therefore, the light reaching the light emitting surface is only in the light emitting window 30 in the central portion,
The p-type AuBe / Au electrode 26 becomes a shadow of the output light,
It does not absorb light.

Further, as shown in FIG. 3E, the light output between the current confinement layers 28 passes through the range indicated by b in the figure. If the light passing through the range b and having an incident angle on the light emitting surface becomes the critical angle θ is L ₁ , only light having an incident angle smaller than this L ₁ is output. The critical angle θ is calculated and the p-type AuBe / Au electrode 26 is provided in a portion where light is incident only at an angle larger than the critical angle θ, so that the light emitting window 30 has a necessary and sufficient size. Further, it is possible to reliably prevent light absorption by the p-type AuBe / Au electrode 26.

In the above-described embodiment, the current confinement layer 28 having a high refractive index is provided and the p-type AuBe / Au electrode 26 is formed on the light emitting surface outside the region having the critical angle on the light emitting surface. When the current confinement layer 28 having a high rate is provided,
The electrode 26 may be formed so that the light emitting window 30 can be widened.

Further, when the current confinement layer 28a does not have a high refractive index, the light emitted from the active layer 23 passes through the current confinement layer 28a and reaches the light emitting surface. At this time,
As shown in FIG. 2, since the current flows between the current confinement layers 28a, the light emitting region thereof is a region surrounded by a vertical line at the end of the current confinement layer 28a and indicated by c (current). Spreads somewhat, but can be ignored because the second cladding layer 24 is thin). Therefore, when the light incident angle of the light emitting surface passes through the range c becomes the critical angle θ and L _2, since only a small light having incident angle than the L ₂ will be output, the light emitting surface Calculate the critical angle θ at
By providing the p-type AuBe / Au electrode 26 in a portion where light is incident only at an angle larger than the critical angle θ, the light emission window 30 can be made necessary and sufficient, and further, the p-type AuBe / Au / It is possible to reliably prevent light absorption by the Au electrode 26.

[0019]

In the light emitting diode device of the present invention, since the current confinement layer having a higher refractive index than that of the second cladding layer is provided in the second cladding layer and the electrode is formed in the peripheral portion of the light emitting surface, The light radiated to the constriction layer is reflected by the current confinement layer and reaches the light emitting surface through the current confinement layers together with other light. Therefore, the light reaching the light emitting surface is in the light emitting window in the central portion. Therefore, the light emission output is not absorbed or shaded by the electrode or the wire connected to the electrode, and a highly efficient and uniform light emission output can be obtained.

When a current confinement layer is provided in the second cladding layer and an electrode is formed on the light emitting surface outside the region where the light emitted from the active layer has a critical angle on the light emitting surface, the light emitting window is further provided. Can be required and large enough,
There is an effect that the light absorption by the electrodes can be prevented more reliably.

[Brief description of drawings]

1A to 1E are process diagrams showing a manufacturing method of an embodiment of a light emitting diode device of the present invention.

FIG. 2 is a schematic view showing another embodiment of the light emitting diode device of the present invention.

FIG. 3 is a schematic diagram showing a relationship between a refractive index and a critical angle.

FIG. 4 is a configuration diagram showing a conventional light emitting diode device.

[Explanation of symbols]

1,21 n-type GaAs substrate 2,22 n-type Al _0.3 Ga _0.7 As first cladding layer 3,23 n-type GaAs active layer 4,24 p-type Al _0.3 Ga _0.7 As second cladding layer 5, 25 n-type electrode 6,26 p-type electrode 7 conductive resin 8 stem 9 gold wire 10 lead 11 light emitting diode element 12 lead frame 27 silicon nitride 28,28a n-type Al _0.8 Ga _0.2 As current constriction layer 29 p-type Al _0.3 Ga _0.7 As contact layer 30 Light emitting window

Claims (2)

[Claims] 1. A light emission having a double hetero structure in which at least a first cladding layer, an active layer, and a second cladding layer having a conductivity type different from that of the first cladding layer are formed in this order on a substrate. In the diode device, the second clad layer is provided with a current confinement layer having a higher refractive index than that of the second clad layer, and electrodes are formed around the back surface of the substrate and the light emitting surface. apparatus. 2. A light emission having a double hetero structure in which at least a first cladding layer, an active layer, and a second cladding layer having a conductivity type different from that of the first cladding layer are formed in this order on a substrate. In the diode device, a current confinement layer is provided on the second cladding layer, an electrode is formed on the back surface of the substrate, and an electrode is formed on a light emitting surface outside a region where light emitted from the active layer has a critical angle on the light emitting surface. A light emitting diode device characterized by being formed.