JPS61281562A - Semiconductor light-emitting element - Google Patents

Abstract

PURPOSE:To improve the efficiency of beam extraction by forming a substrate into a P-type having high impurity concentration and an upper clad layer into an N-type and fitting a ring-shaped ohmic electrode onto the upper clad layer while low reflectivity insulators are mounted inside and outside the ring of the ohmic electrode. CONSTITUTION:An N-type GaAs current block layer 32, a hole 34 for a current path, a P-type AlGaAs layer clad layer 36, a P, N or non-doped type AlGaAs active layer 38 and an N-type AlGaAs upper clad layer 40 are shaped onto a P-type GaAs substrate 30 and a first electrode 42 onto the lower surface of the substrate 30. A second electrode, through the inside thereof a beam extracting region 44 is surrounded, a ring-shaped ohmic electrode 45, is formed onto the surface of the upper clad layer 40, and low reflectivity films 48 consisting of insulators are each shaped onto the surfaces of the upper clad layers 40 on the outside and inside of the ohmic electrode 46. A metallic layer 50 for wire bonding is formed onto the ring-shaped ohmic electrode 46 and the low reflectivity film 48a. Accordingly, surface reflection in a light-emitting section is removed, thus improving the efficiency of beam extraction by approximately 30%.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a semiconductor light emitting device for communication, particularly a surface emitting device.

(Prior Art) Various surface-emitting type semiconductor optical devices of this type have been proposed in the past. ? FIG. 3 is a perspective view showing a main part in cross section, showing the element structure previously proposed by the inventors of this application. This conventionally proposed device structure is an internal current confinement structure using a p-type GaAs substrate, and the ballast structure also aims to achieve the same level of luminous efficiency as the ballast structure (Reference: [31st Applied Physics Related Union Lecture Proceedings J, 31a, -E-
3).

As shown in FIG. 3, this device structure consists of a current confinement n
Type GaAs layer (hereinafter also referred to as current blocking layer) 12
Ingredients and ingredients. In this n-type GaAs layer 12, a hole 14 is formed that reaches the substrate 10 from its surface and serves as a current path. layer 18
, n-type AuzGaI-zAs upper cladding layer 20 and n
A GaAs type ohmic contact layer 22 is grown. Furthermore, a window 24 for light extraction reaching the upper cladding layer 20 is formed in this ohmic contact layer 22 .

In this element structure, the current flows only through the hole 14 formed in one layer 12 in the current I, efficiently concentrates on the curved part near the center of the light emitting layer 18, and passes through the light extraction window 24 through the -I
It emits light on one side.

(Problems to be Solved by the Invention) However, with such a conventional device structure, in order to form the light extraction window 24, the ohmic contact layer 22 must be extended until it reaches the upper cladding layer 20. It is necessary to perform etching. As a result, the AuGaAs of the upper cladding layer 20 is exposed and an An oxide film is formed, resulting in a problem of loss of optical output.

Furthermore, the light is reflected by the surface of this upper cladding layer into three
Approximately 3% of the light was reflected, which also contributed to the decrease in light output.

Therefore, the object is to provide a semiconductor light emitting device having a structure that eliminates the need for an etching process that causes loss of light output and improves light extraction efficiency.

(Means for Solving the Problems) In order to achieve this object, the semiconductor light emitting device of the present invention is provided with an internal current blocking layer, a lower cladding layer, an active layer, and an upper cladding layer on a substrate. A semiconductor light emitting device is provided.

Then, this substrate is made into a p-type substrate with high impurity concentration.
The - side cladding layer is made of n-type, which facilitates the formation of ohmic contact.

A ring-shaped ohmic electrode is provided directly on the upper cladding layer 2, and low reflectance insulators are provided on the inside and outside of the ring of the ohmic electrode. In this case, low reflectance means a reflectance that makes the conventional surface reflectance substantially O or approaches a value close to this.

(Function) According to such a structure, since the ring-shaped ohmic electrode can be directly attached to the upper cladding layer, the conventional growth process and the process of etching a window for light extraction are unnecessary. Therefore, surface roughness caused by opening the window can be prevented and light extraction efficiency can be increased.

Further, according to the structure of the present invention, since a low reflectance film made of an insulator is provided on the side cladding layer portion corresponding to the light extraction window, surface reflection of this upper cladding layer can be eliminated and light can be extracted. Efficiency can be increased by about 30% or more compared to conventional methods.

Furthermore, a ring-shaped ohmic electrode is used, and an insulator is provided on the -L side cloud layer outside the light extraction window area outside the ring-shaped ohmic electrode, so that current does not flow in the element area that is not involved in light emission. Therefore, leakage current can be reduced and luminous efficiency can be increased.

(Example) Hereinafter, an example of the semiconductor light emitting device of the present invention will be described with reference to FIGS. 1 and 2.

It should be noted that these figures are only schematic representations to the extent that the present invention can be understood, and the dimensions, shapes, and arrangement relationships of each component are not limited to the illustrated examples. Also, in the figure,
Hatching etc. indicating the cross section are omitted except for some parts. In this embodiment, an example using a p-type GaAs substrate will be explained.

FIG. 1 is a partial perspective view showing the structure of a light emitting element, and a cross section of a portion of the light emitting element is shown with the light emitting center opened.

In the case of this light emitting element, as in the conventional case, an n-type GaAs current blocking layer 32 is formed on a p-type GaAs substrate 30, and a current path hole (also called an internal window) 3 with a diameter of about 30 #Lm, for example.
4. p-type AJljGaAs lower rad layer 36, p, n
Or non-doped AsGaAs active layer (light emitting layer) 38
, an n-type AJJGaAs upper rad layer 40. A first electrode (p-side electrode in this embodiment) 42 is provided on the lower surface of the substrate 30.

In the device structure of this invention, the second cladding layer 40
A second electrode, that is, a ring-shaped ohmic electrode (in this embodiment, an n-side electrode) 46 is provided on the surface of the light extraction region 44 so as to surround the light extraction region 44 inside. Low reflectance films 48a and 48 made of an insulator are provided on the surface of the -L side rad layer 40 on the outside and inside of this ohmic electrode 46, respectively.
b (representatively indicated by 48). This insulating low reflectance film 48 is made of, for example, CeO, SixNy, Si.
It is composed of xOyNz, 5102/a-S i, Au203, etc.

This ring-shaped ohmic electrode 46 and low reflectance film 48a
''-, a metal layer 50 for wire bonding is provided. This metal layer 50 is formed of a metal such as Au-Cr that has good adhesion to the lower low reflectance film 48a.

In order to clarify the structure of such a light emitting device, a method for manufacturing this device will be briefly explained.

FIG. 2 is a schematic plan view of this element with the metal layer 50 on the light extraction side removed.

First, the substrate 3 is fabricated using normal semiconductor technology as in the past.
A current element layer 32 is grown on 0-1-, an internal current path window 34 is opened, and a lower cladding layer 36, an active layer 38 and an upper cladding layer are sequentially formed on the upper side of the window 34 to form a double heterojunction structure. 3. Grow layer 40. Next, a low reflectance film 48 made of an insulator is applied to the surface of this upper cladding layer 40. As a method for applying this film 48, various commonly used methods including a vapor deposition method can be used.

Next, this low reflectance film 48 is provided with an inner diameter (for example, 50 ILm) that is large enough to surround the light extraction region 44 inside.
Then, a ring-shaped hole 52 having a width of, for example, about 20 pm and a depth reaching the surface of the underlying upper cladding layer 40 is provided (see FIG. 2).

Thereafter, the n-type ohmic electrode 4 is inserted into the ring-shaped hole 52.
B For example, attach AuGeNi. This ohmic electrode 4
As a method for depositing the material No. 8, various conventionally used methods such as vapor deposition can be used. Next, a metal layer 50 made of, for example, Cr--Au, which has good adhesion to an insulator, is provided on the ring-shaped ohmic electrode 4B and the low reflectance film 48a, excluding the portion of the low reflectance film 48b that becomes the light emitting part.

Note that it is also possible to form this metal layer 50 first and then provide the ohmic electrode 46.

Furthermore, the substrate 30, the current blocking IL layer 32, the lower cladding layer 3B, and the -L side rad layer 40 are made of InP layers, and the active layer 38 is made of GaxInl-xAsyPt-7.
It is also possible to set the oscillation wavelength to 1.0 to 1.
．． A light emitting device of 6 ILm is obtained.

Next, the operation of this element will be briefly explained.

When a voltage is applied between the p-side electrode 42 and the ring-shaped ohmic electrode 46 on the n-side, electrons injected from the ohmic electrode 46 and electrons injected from the p-side electrode 42 through the internal window 34 are generated. The holes efficiently concentrate on the curved portion of the active layer 38 and recombine to emit light. This light is extracted from the light extraction area 4.
4 to the outside through a low reflectance film 48b. At this time, because of the low emissivity film 48b, the light does not return inside due to surface reflection and is efficiently output. For this reason,
The light output is increased by about 30% compared to the conventional method.

(Effects of the Invention) As is clear from the above explanation, the semiconductor light emitting device of the present invention does not have an ohmic contact layer, so a growth process for the ohmic contact layer and an etching process for forming light extraction holes are necessary. Therefore, oxidation of the light extraction surface can be prevented and the output can be increased.

Furthermore, since the upper cladding layer is provided with a ring-shaped ohmic electrode directly and a low reflectance film made of an insulator is provided on the outer and inner surfaces of the ring-shaped ohmic electrode, surface reflection of the light emitting part is eliminated, and the light extraction efficiency is approximately Increase by 30%.

Furthermore, a structure in which an insulator is provided outside the ohmic electrode'
Therefore, no electric current flows in areas other than those involved in light emission, resulting in a light-emitting element with high current efficiency. 1

[Brief explanation of drawings]

FIG. 1 is a perspective view schematically showing an embodiment of the semiconductor light emitting device of the present invention, with main parts taken in section, FIG. 2 is a plan view from the light extraction side showing a part of FIG. 1, and FIG. FIG. 2 is a perspective view showing a conventional semiconductor light emitting device. 30... Substrate, 32... Current blocking layer 3
4... Current path hole (or internal window) 36... Lower cladding layer, 38... Active layer (light emitting layer) 40... Upper cladding layer, 42... First electrode 44...・Light image extraction area 46...second electrode (ring-shaped ohmic electrode) 48・
...Low reflectance film, 50...Metal layer 52...Ring-shaped hole. Patent applicant: Oki Electric Industry Co., Ltd. N Daisai
(Q 60 <5) “i”s ~)
! 3rd figure - ri [ri - f) mochi tsude

Claims (1)

[Claims] (1) An internal current blocking layer and a lower cladding layer on the substrate,
In a semiconductor light emitting device comprising an active layer and an upper cladding layer, the substrate is p-type and the upper cladding layer is n-type, further comprising a ring-shaped ohmic electrode on the upper cladding layer, and a ring-shaped ohmic electrode on the upper cladding layer. A semiconductor light emitting device comprising a low reflectance insulator on the inside and outside of an electrode ring.