JPH0217683A - Current constriction type light-emitting diode - Google Patents

Abstract

PURPOSE:To improve the efficiency of light extraction, and to prevent the leakage of operating currents by forming current constriction layers inhibiting operating currents with the exception of specified conduction regions between a second clad layer and an active layer and/or between the second clad layer and an upper electrode. CONSTITUTION:An electrode 26 is shaped onto an insulating film 24, and brought into contact with a contact layer 20 in a peripheral section in an opening 22. Consequently, operating currents flow from the electrode 26 to the contact layer 20 within the specified range of the opening 22, and the passage region of operating currents reaches to an electrode 30 through a second clad layer 18, an active layer 16, a first clad layer 14 and a substrate 12 while being slightly spread. Since the contact layer 20, the second clad layer 18 and the active layer 16 are made extremely thinner than the substrate 12 at that time, the conduction region of the active layer 16 is approximately equalized to the opening 22. Accordingly, the insulating film 24 functions as a current constriction layer, a light-emitting section in the active layer 16 is scaled down, and the efficiency of light extraction is improved while the leakage of operating currents can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a surface-emitting type light emitting diode having a double heterostructure, and more particularly to a current confinement type light emitting diode in which a light emitting part is made smaller by narrowing the operating current carrying area. It is something.

A first cladding layer, an active layer, and a second cladding layer are sequentially stacked on a conventional technology substrate, and an operating current is passed between an upper electrode provided on the second cladding layer and the substrate. Accordingly, surface-emitting double heterostructure light-emitting diodes that extract light generated within an active layer from a light extraction surface parallel to the active layer are widely known. A type of light emitting diode is a ballast, which has a smaller light emitting part by narrowing the operating current carrying area.
There is a type of light emitting diode.

The light emitting diode 50 shown in FIG.
A first cladding layer 54 consisting of lo, xsG ao, and bsA S. an active layer 56 made of p-GaAs; a second cladding layer 58 made of p-GaAs; and a contact layer 60 made of p-GaAs of 5 μm, 0.5 μm, and 2 μm, respectively.
m, with a film thickness of 0.1 μm. In addition, the board 5
By removing the central portion of the substrate 52 by etching or the like, a light extraction member 62 for extracting the light generated within the active layer 56 is provided, and the substrate 52 is provided with a light extraction member 62.
While a u-Ge n-type ohmic electrode 64 is attached, a 5iOz insulating film 66 is formed on the contact layer 60, and an opening 68 is formed in the center of the insulating film 66 to connect the Au-Zn p-type ohmic electrode 64. An ohmic electrode (upper electrode) 70 is attached.

In such a light emitting diode 50, the forward direction, that is, the electrode 70 is connected between the pair of electrodes 64 and 70.
When an operating current is passed from the side toward the electrode 64, light is generated within the active layer 56, and the light is extracted from the light extraction surface 62. However, due to the presence of the insulating film 66, the area where the operating current is applied is Since the light is confined within the opening 68, the light emitting portion within the active layer 56 becomes smaller, and the amount of light that deviates from the light extraction surface 62 is reduced, resulting in high light extraction efficiency. For this reason, for example, the optical fiber input when connecting with an optical fiber is greatly improved.
It is suitably used as a light source for optical fibers. Note that the size of the opening 68 is determined based on the core diameter of the optical fiber to be connected.

Problems to be Solved by the Invention However, since such rose-type light emitting diodes have an upside-down structure that extracts light from the substrate side, the conductive paste that protrudes from the periphery when bonding to the stem may damage the insulating film. There was a fear that the operating current would leak from the outside and the current confinement effect by the insulating film 9 would no longer be obtained. In addition, since it is necessary to remove a large part of the center of the board, processing is troublesome, and since the thickness of the board at the center is extremely thin, stress is applied to the light emitting part, resulting in a reduction in light output. Ta.

The present invention has been made against the background of the above circumstances, and aims to eliminate the risk of leakage due to conductive paste during bonding, reduce the decrease in optical output due to stress, and facilitate processing. An object of the present invention is to provide a current confinement type light emitting diode.

Means for Solving the Problems In order to achieve the above object, the present invention provides a first method on a substrate.
A cladding layer, an active layer, and a second cladding layer are sequentially laminated, and an operating current is passed between the upper electrode provided on the second cladding layer and the substrate, so that an electric current is generated in the active layer. In a surface-emitting type double-hetero structure light emitting diode that extracts generated light from a light extraction surface provided on the second cladding layer side, the second cladding layer is provided between the second cladding layer and the active layer and/or the second cladding layer. The present invention is characterized in that a current confinement layer is provided between the upper electrode and the upper electrode for inhibiting the flow of the operating current except for a predetermined current-carrying region.

The current confinement layer is preferably formed by forming an insulator with high electrical resistance or a semiconductor having a conductivity type opposite to that of the second cladding layer, and providing an opening in a portion corresponding to the current-carrying region. be done. However, if the active layer and the second cladding layer have different conductivity types and a current confinement layer is provided between them, the current confinement effect will not occur even if a semiconductor with the conductivity type opposite to that of the second cladding layer is formed. Since this is not possible, an insulator or the like with high electrical resistance must be provided.

Operation and Effects of the Invention In such a current confinement type light emitting diode, a current confinement provided between the second cladding layer and the active layer, between the second cladding layer and the upper electrode, or both thereof. Since the operating current is caused to flow only through a predetermined current-carrying region by the layer, the light-emitting portion of the active layer is made smaller corresponding to the current-carrying region, and the light extraction efficiency is improved. Moreover, because it has an upside-up structure with a light extraction surface on the opposite side of the board, even if the conductive paste protrudes to the periphery when bonding to the stem, the thick board prevents the conductive paste from leaking out. There is no danger that the paste will reach the current confinement layer, and leakage of operating current due to the conductive paste is prevented, so that a good current confinement effect can always be obtained. Further, since it is sufficient to simply provide a current confinement layer, there is no need for troublesome processing to remove the substrate, high mechanical strength is obtained, and a decrease in optical output due to stress is reduced.

EXAMPLE Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 1 is a structural diagram of a current confinement type light emitting diode 10 which is an embodiment of the present invention.
A first cladding layer 14 made of Alo, a Gao, and b As. Active layer 16 made of p-GaAs. p-Al
The second cladding N18.o, , Gao, , As.
Contact layers 20 made of p-GaAs and p-GaAs are sequentially laminated with film thicknesses of 2 μm, 0.5 μm, 5 μm, and 0.1 μm, respectively. Further, on the contact layer 20, a 5in2 insulating film 24 with a thickness of 0°1 μm is provided, and an opening 22 with a diameter of 50 μm is formed in the center. The Au-Zn p-type ohmic electrode 2 is brought into contact with the contact layer 20.
6 is attached, and a light extraction layer 28 parallel to the active layer 16 is formed inside this electrode 26. Also,
The substrate 12 has an n-type ohmic electrode 3 of Au-Ge.
0 is attached.

Note that the first cladding layer 14. Active layer 16. Second cladding layer 18. and the carrier concentration of the contact layer 20 are lXl0■c+n-32X10"cm-3, respectively.
, I X I O"cm-3,5X 10111cm-
". Furthermore, the first cladding layer 14, the active layer 16, and the second cladding layer 18 constitute a double heterostructure.

Such a light emitting diode 10 is manufactured, for example, as follows.

That is, first, metal organic chemical vapor deposition (MOCVD;
Metal Organic Chemical Va
The first cladding layer 14 is doped with Se, and the active layer 16. The second cladding layer 18 and the contact layer 20 are sequentially grown by doping Zn at a growth temperature of 800°C. Next, chemical vapor deposition (CVD)
After coating the entire surface of the contact layer 20 with the insulating film 24 using the etchant deposition method, the openings 22 are etched using an etching solution (HF aqueous solution) using the photolithography technique.
form. Finally, after depositing the electrodes 26 and 30, annealing (heat treatment) at 400° C. for 5 minutes is performed to manufacture the intended light emitting diode 10.

In such a light emitting diode 10, an operating current is passed between the pair of electrodes 26 and 30 in the forward direction, that is, from the electrode 26 to the electrode 30, so that the active layer 1
6, the light is generated in the light extraction surface 2.
It is taken out from 8.

At this time, the electrode 26 is provided on the insulating film 24 in which the opening 22 is provided, and is brought into contact with the contact layer 20 at the periphery within the opening 22, so that the operating current flows through the opening 22.
It flows from the electrode 26 to the contact layer 20 within a range of 50 μm in diameter.

Thereafter, the area where the operating current flows is slightly expanded and the second cladding layer 18. Active layer 16. First cladding layer 14. and through the substrate 12 to the electrode 30, but contacts N20. Since the second cladding layer 18 and the active layer 16 are extremely thin compared to the substrate 12, the active layer 16
The current-carrying area, that is, the area of the light emitting part within the opening 22 is limited to a diameter of approximately 50 μm, which is approximately the same as the opening 22.

In this embodiment, the insulating film 24 corresponds to a current confinement layer,
The inner part of the opening 22 corresponds to the current-carrying area.

Further, the electrode 26 provided on the insulating film 24 is an upper electrode.

2, in the light emitting diode 10 of this embodiment, since the light emitting part in the active layer 16 is small, the amount of light that deviates from the light extraction surface 28 is reduced, resulting in high light extraction efficiency. The optical fiber input at the time of connection is greatly improved, and it can be suitably used as a light source for optical fibers.

Incidentally, by using such a light emitting diode 10 (product of the present invention) and a conventional product of full-emission type in which the insulating film 24 is not provided, they are each mounted on a Tθ18 stem, and the core diameter is 50 μm and the NA is (Numerical aperture = acceptance angle θ
,,,)0.2. When the fiber was coupled to a G1-50 type multimode fiber with a flat end face using the direct coupling method and the human power (μW) applied to the fiber was measured, the results shown in Table 1 were obtained. From these results, it can be seen that the product of the present invention has a significantly improved fiber insertion angle compared to the conventional product. Note that the operating current 1. (mA), optical output (external light output) Po (m
W) is as shown in the table.

Table 1 On the other hand, the light emitting diode 10 of this embodiment has an upside-up structure in which the light extraction surface 28 is provided on the side opposite to the substrate 12 and is mounted on the stem on the substrate 12 side, so that it is difficult to bond to the stem. Even if the conductive paste protrudes to the periphery, the conductive paste is insulated because the board 12 is thick (usually several hundred μm). i! 2
4, leakage of the operating current due to the conductive paste is prevented, and the current confinement effect by the insulating film 24 can always be obtained satisfactorily.

In addition, since it is sufficient to form the insulating film 24 on the contact layer 20 and provide the opening 22, there is no need for troublesome processing to remove the substrate 12 as in the case of a ballad type light emitting diode, and the device has high mechanical strength. As a result, the decrease in optical output due to stress is reduced. In particular, in this embodiment, since the insulating film 24 is provided on the contact layer 20, the first cladding layer 14. Active layer 16. Second cladding M18. In addition, the contact layer 20 can be grown continuously by the metalorganic chemical vapor deposition method, etc., and its manufacture becomes easier.

Next, another embodiment of the present invention will be described. In the following embodiments, parts common to those in the first embodiment are given the same reference numerals and detailed explanations will be omitted.

In the current confinement type light emitting diode 40 shown in FIG. 2, instead of providing the insulating film 24 on the contact layer 20, an opening 42 with a diameter of 50 μm is formed between the active layer 16 and the second cladding layer 18. r, -GaA with a thickness of about 2 μm
s semiconductor 44 is provided. In this case, since the direction of the operating current is reverse biased between the semiconductor 44 and the active layer 16, the operating current does not flow through the semiconductor 44 to the active layer 16, but inside the opening 42 of the semiconductor 44. The light flows directly from the first cladding layer 18 to the active layer 16, thereby limiting the area of the light emitting part within the active layer 116 to a diameter of 50 μm. In this embodiment, the semiconductor 44 corresponds to a current confinement layer, and the inner portion of the opening 42 corresponds to a current-carrying region. The light emitting diode 40 is manufactured by forming the first cladding layer 14 and the active layer 16 on the substrate 12 by, for example, the organometallic chemical vapor deposition method.
After growing on the active layer 16, Se is subsequently grown on the active layer 16.
The semiconductor 44 is grown by doping, and an etching solution (NHaOH+
After that, the second cladding layer 18 and the contact layer 20 may be grown again by a metal organic chemical growth method or the like. Further, on the contact layer 20, an electrode (upper electrode) 48 having an opening 46 of approximately the same size is provided directly above the opening 42, and the inside of the opening 46 serves as the light extraction surface 28.

Although the embodiments of the present invention have been described above in detail based on the drawings, the present invention can also be implemented in other embodiments.

For example, in the first embodiment, the SiO□ insulating film 24 is provided as a current confinement layer on the contact layer 20;
Provide other high electrical resistance insulators such as 5izN4,
Various current confinement layers can be employed, such as an n-type semiconductor as in the second embodiment, or a single crystal semiconductor grown and doped with an impurity such as Fe that increases the electrical resistance. Also in the embodiment shown in FIG.
Similarly, in place of the semiconductor 44, a current confinement layer having another structure can be provided.

Further, instead of providing a current confinement layer on the contact layer 20, a current confinement layer may be provided between the second cladding layer 18 and the contact layer 20.

Further, in the second embodiment, the opening 42 is formed in the n-type semiconductor 44, but by locally doping with an acceptor such as Zn, it is possible to provide a conductive region without forming the opening 42. is also possible. On the contrary, p
It is also possible to form a current confinement layer by forming a type semiconductor and doping a donor such as Se or an impurity that increases electrical resistance in a portion other than the current conducting region.

Furthermore, in the above embodiments, a manufacturing method using metal-organic chemical vapor deposition was explained, but molecular beam epitaxy,
Various other manufacturing methods can be employed, such as those using vapor phase epitaxy and liquid phase epitaxy.

Furthermore, in the above embodiment, G a A s / A Q G
a As double heterostructure light emitting diode 10.
40, but GaP, InP, InGaA
The present invention can be similarly applied to a double heterostructure light emitting diode made of sP or the like.

Further, the film thickness and composition ratio of each layer of the light emitting diode 10.40, the size of the openings 22, 42.46, etc. can be changed as appropriate.

Furthermore, in the above embodiment, the second cladding layer 18 is a p-type semiconductor! However, the present invention can be similarly applied to a light emitting diode in which the second cladding layer 18 is an n-type semiconductor.

Although other examples are not provided, the present invention can be implemented with various modifications and improvements based on the knowledge of those skilled in the art.

[Brief explanation of the drawing]

FIG. 1 is a structural diagram of a current confinement type light emitting diode which is an embodiment of the present invention. FIG. 2 is a structural diagram of another embodiment of the present invention. FIG. 3 is a structural diagram of a conventional ballast type light emitting diode. Figure 1 10.40: Current confinement type light emitting diode 12: Substrate
14: First cladding layer 16: Active layer
18: Second cladding layer 22.427 opening 24: Insulating film (current confinement layer) 26.48: Electrode (upper electrode) 28: Pre-extraction surface 44: Semiconductor (current confinement layer)

Claims (3)

[Claims] (1) A first cladding layer, an active layer, and a second cladding layer are sequentially laminated on a substrate, and an operating current is passed between an upper electrode provided on the second cladding layer and the substrate. In a surface-emitting type double-hetero structure light emitting diode in which light generated in the active layer is extracted from a light extraction surface provided on the second cladding layer side, between the second cladding layer and the active layer. and/or a current confinement type light emitting diode, characterized in that a current confinement layer is provided between the second cladding layer and the upper electrode to inhibit the flow of the operating current except for a predetermined current-carrying region. . (2) The current confinement type light emitting diode according to claim 1, wherein the current confinement layer is an insulator with high electrical resistance and has an opening provided in a portion corresponding to the current-carrying region. (3) The current confinement type light emitting device according to claim 1, wherein the current confinement layer is a semiconductor having a conductivity type opposite to that of the second cladding layer, and has an opening provided in a portion corresponding to the current-carrying region. diode.