JP2004304050A - Light emitting diode - Google Patents

Abstract

Provided is a light-emitting diode that emits light at a low operating voltage and does not cause peeling of a transparent conductive film due to dicing or the like and that can achieve high luminance.
A p-type AlGaAs layer containing at least aluminum and having a zinc concentration of 1 × 10 ¹⁹ cm ⁻³ is provided as a transparent conductive film peeling prevention layer as a semiconductor layer in contact with the transparent conductive film. Thus, the peeling phenomenon of the transparent conductive film 7 can be suppressed, and the yield of manufacturing the light emitting diode can be significantly improved.
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a light-emitting diode composed of an AlGaInP-based compound semiconductor, and more particularly to a light-emitting diode that prevents peeling of a metal oxide transparent conductive film, has high luminance, and can be manufactured at low cost.
[0002]
[Prior art]
Conventionally, most of light emitting diodes have a green color of GaP (gallium phosphide) and a red color of AlGaAs (aluminum gallium arsenide). However, in recent years, a technology for growing a GaN (gallium nitride) -based or AlGaInP (aluminum-gallium-indium phosphide) -based crystal layer by a MOVPE (Meta1 Organic Vapor Phase Epitaxy) method has been developed, and a red color has been developed. In addition, light emitting diodes having desired emission wavelengths such as orange, yellow, green, and blue can be manufactured.
[0003]
In a light emitting diode, in order to obtain high luminance, it is important to emit light uniformly in the chip, and for that purpose, it is necessary to improve current distribution. As a method for solving this problem, a method of increasing the thickness of the current distribution layer is known. However, the cost of the current distribution layer in manufacturing an epitaxial wafer for a light emitting diode is increased, and as a result, the light emission is increased. There is a disadvantage that the cost for manufacturing the epitaxial wafer for the diode is increased.
[0004]
In order to reduce the manufacturing cost of the light emitting diode, it is preferable to reduce the thickness of the current dispersion layer. This requires an epitaxial layer having a low film resistance and an epitaxial layer having a high carrier concentration. However, it is difficult to grow a p-type epitaxial layer having a high carrier concentration with a material such as AlGaInP or GaN. Further, any other semiconductor having the above-mentioned characteristics can be used instead, but a semiconductor satisfying such characteristics has not been found.
[0005]
As another method, it is known that a metal film is used as a transparent electrode (transparent conductive film) in a GaN-based light emitting diode. In this case, the metal film is made extremely thin in order to increase the light transmittance. And the current dispersion effect is reduced. On the other hand, if an attempt is made to obtain a current dispersion effect, the thickness of the metal film becomes large, which impairs the light transmission.
[0006]
An ITO (Indium Tin Oxide) film, which is a metal oxide film, is a film having sufficient light transmission characteristics and having electric characteristics to obtain a current dispersion effect. There is a light emitting diode using this ITO film as a current dispersion layer (for example, see Patent Document 1). According to this light emitting diode, an epitaxial layer as a current distribution layer can be dispensed with, so that a high-brightness light emitting diode can be produced at low cost.
[0007]
FIG. 2 is a cross-sectional structure of a light emitting diode described in Patent Document 1.
The light emitting diode 20 is a red light emitting diode having a light emission wavelength of about 630 nm, and has an n-type GaAs substrate 1 and an n-type (selenium-doped) (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P cladding layer 2. And an undoped (Al _0.15 Ga _0.85 ) _0.5 In _0.5 P active layer 3, and a p-type (zinc-doped) (Al _0.7 Ga _{0 .5} ) having a zinc concentration of 5 × 10 ¹⁷ cm ⁻³ _{. 3} ) a _0.5 In _0.5 P cladding layer 4, a p-type GaP layer 5, a p-type InP compound semiconductor layer 6A, a transparent conductive film 7, and an n-type electrode 8 formed on the entire chip bottom surface; It is configured by laminating a circular p-type electrode 9 with a diameter of 150 μm on the upper surface.
Each layer from the n-type GaAs substrate 1 to the p-type AlGaInP cladding layer 4 is formed by MOVPE. MOVPE growth is performed at a growth temperature of 700 ° C., a growth pressure of 50 Torr, and a growth rate of each layer of 0.3 to 1.0 nm. / S, V / III ratio is 300-600.
[0009]
The p-type GaP layer 5 is formed by growing 2 μm at a zinc concentration of 1 × 10 ¹⁸ cm ⁻³ , a V / III ratio of 100, and a growth rate of 1 nm / s.
[0010]
The p-type InP compound semiconductor layer 6A is formed with a zinc concentration of 1 × 10 ¹⁸ cm ⁻³ , and is provided as a base layer of the transparent conductive film 7 so that the transparent conductive film 7 is separated from the epitaxial wafer by dicing or the like. To prevent
[0011]
The transparent conductive film 7 is made of an ITO film, and is formed by a vacuum deposition method. The deposition conditions of the ITO film are about 200 nm at a substrate temperature of 250 ° C. and an oxygen partial pressure of 4 × 10 ⁻⁴ Torr.
[0012]
The n-type electrode 8 is formed by depositing gold, germanium, nickel, and gold in order of 60 nm, 10 nm, and 500 nm, respectively.
[0013]
The p-type electrode 9 is formed by depositing gold, zinc, nickel, and gold in the order of 60 nm, 10 nm, and 1000 nm, respectively.
[0014]
The light emitting diode 20 is formed by cutting an LED-equipped LED-equipped wafer laminated in the above-described configuration to a chip size of 300 μm square by dicing. In the process such as dicing, the transparent conductive film 7 is cut while maintaining the adhesion to the p-type InP compound semiconductor layer 6A. The light emitting diode 20 is die-bonded on the TO-18 stem, and is electrically connected to the TO-18 stem by wire bonding.
[0015]
[Patent Document 1]
JP 2002-344017 A (FIG. 2)
[0016]
[Problems to be solved by the invention]
However, according to the conventional light emitting diode, the junction between the light emitting diode having a pn junction and the transparent conductive film 7 becomes substantially npn, and the interface between the transparent conductive film 7 and the p-type InP compound semiconductor layer 6A is formed by a barrier. Although a series resistance is generated, the amount of reduction in the series resistance is not sufficient according to the zinc concentration (1 × 10 ¹⁸ cm ⁻³ ) of the transparent conductive film 7, so that a high operating voltage is required to emit light. Further, since a thickness (30 nm) for obtaining a sufficient current dispersion characteristic is required, there is a problem that it becomes an obstacle in achieving high luminance.
[0017]
Accordingly, an object of the present invention is to provide a light emitting diode which does not cause peeling of a transparent conductive film due to dicing or the like, emits light at a low operating voltage, and can realize high luminance.
[0018]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a semiconductor substrate, a light emitting unit provided on the semiconductor substrate and at least an active layer sandwiched between cladding layers of different conductivity types, and provided on the light emitting unit. A transparent conductive film peel-prevention layer comprising a compound semiconductor containing at least aluminum and having a conductivity-type-determining impurity at a concentration of 1 × 10 ¹⁹ cm ⁻³ or more; and a transparent film made of a metal oxide provided on the transparent conductive film-peeling prevention layer A light-emitting diode comprising: a conductive film; a surface electrode provided on the transparent conductive film; and an electrode provided on the entire surface or a part of the back surface of the semiconductor substrate.
[0019]
According to this structure, the transparent conductive film is prevented from being separated by the transparent conductive film separation preventing layer, and the current dispersion characteristics are improved, so that light emission can be performed at a low voltage.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0021]
(First Embodiment)
FIG. 1 is a cross-sectional structure of a light emitting diode according to a first embodiment of the present invention.
This light-emitting diode 10 is a red light-emitting diode having an emission wavelength of about 630 nm, and has an n-type GaAs substrate 1 and an n-type (selenium-doped) (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P cladding layer 2. And an undoped (Al _0.15 Ga _0.85 ) _0.5 In _0.5 P active layer 3, and a p-type (zinc-doped) (Al _0.7 Ga _{0 .5} ) having a zinc concentration of 5 × 10 ¹⁷ cm ⁻³ _{. 3} ) _0.5 In _0.5 P clad layer 4, p-type GaP layer 5, p-type (zinc-doped) AlGaAs layer 6 as a transparent conductive film separation preventing layer, and transparent conductive film 7 made of an ITO film And an n-type electrode 8 formed on the entire bottom surface of the chip and a p-type electrode 9 formed on the upper surface in a circular shape having a diameter of 150 μm. The epitaxial growth method, the epitaxial structure, the method of forming the ITO film, and the like are the same as those of the light emitting diode 20 described with reference to FIG.
[0022]
The AlGaAs layer 6 is formed on the p-type GaP layer 5 with a thickness of 10 nm, and is provided so that the zinc concentration is 1 × 10 ¹⁹ cm ⁻³ or more, and the Al composition is 0.1 and 0.4. , 0.8.
[0023]
The light emitting diode 10 is formed by cutting the LED-equipped LED-equipped wafer stacked in the above-described configuration to a chip size of 300 μm square by dicing. In the process such as dicing, the transparent conductive film 7 is cut while maintaining the adhesion to the p-type AlGaAs layer 6. The cut light-emitting diode 10 is die-bonded on the TO-18 stem, and is electrically connected to the TO-18 stem by wire bonding.
[0024]
According to the light emitting diode 10 described above, it has been confirmed that the peeling phenomenon of the transparent conductive film 7 is about 1% or less in all the light emitting diode chips in which the Al composition is changed, and the semiconductor layer to which the transparent conductive film 7 is in contact. By using the AlGaAs layer 6 as a layer containing at least Al, the peeling phenomenon can be suppressed, and the yield of manufacturing a light emitting diode can be greatly improved.
[0025]
In addition, since the AlGaAs layer 6 can be formed as thin as 10 nm, the light extraction property is improved, high luminance can be realized, and the amount of raw materials used can be reduced, thereby reducing the manufacturing cost.
[0026]
The peeling phenomenon of the transparent conductive film 7 from the semiconductor layer largely depends on the Al (aluminum) composition in the compound semiconductor. In the present invention, it has been found that the peeling of the transparent conductive film 7 is suppressed by containing at least Al. That, Al composition contained in the transparent conductive film peeling prevention layer, must be at least 0.01 or more, does not contain _{Al Ga X In 1-X P} (0 ≦ X ≦ 1), Ga X In 1 Compound semiconductors such as _-X As (0 ≦ X ≦ 1) are not suitable.
[0027]
The transparent conductive film 7 described in the first embodiment is an n-type metal oxide, and the junction with the light emitting diode having a pn junction is substantially npn. At the interface with the type AlGaAs layer 6, a series resistance is generated due to a barrier. To reduce or eliminate this problem, the p-type AIGaAs layer 6 requires a high carrier concentration, specifically, a high impurity concentration. Therefore, it is desirable that the conductivity type determining impurity concentration contained in the p-type AlGaAs layer 6, that is, the zinc concentration is 1 × 10 ¹⁹ cm ⁻³ or more.
[0028]
In the first embodiment described _above, has been described _{(Al X Ga 1-X)} Y In 1-Y P (0 ≦ X ≦ 1,0 ≦ Y ≦ 1) 4 -element light emitting diodes, such as For example, even for a ternary light emitting diode such as AlGaAs, by providing the above-mentioned transparent conductive film peeling prevention layer, the peeling phenomenon of the transparent conductive film can be prevented.
[0029]
In order to increase the luminance of the light emitting diode, for example, a light reflection layer such as a distributed Bragg reflection layer (DBR) may be provided between the GaAs semiconductor substrate and the n-type cladding layer.
[0030]
(Second embodiment)
As a second embodiment of the present invention, a p-type (zinc-doped) AlInAs layer having a thickness of 10 nm is formed as a transparent conductive film separation preventing layer on a p-type GaP layer, and the Al composition contained in the AlInAs is respectively adjusted. A red light emitting diode having an emission wavelength of about 630 nm with 0.1, 0.4, and 0.8 was produced. The other configurations, the epitaxial growth method, the epitaxial structure, the method of forming the ITO film, and the like are the same as those of the first embodiment, and thus redundant description will be omitted.
[0031]
Further, the light emitting diode is formed by cutting the above-described epitaxial wafer including the p-type AlInAs layer into a chip having a chip size of 300 μm by dicing in the same manner as in the first embodiment. In this step such as dicing, the transparent conductive film is cut while maintaining the adhesion to the p-type AlGaAs layer. The cut light emitting diode is die-bonded on the TO-18 stem, and is electrically connected to the TO-18 stem by wire bonding.
[0032]
According to the light emitting diode of the second embodiment described above, even when the AlInAs layer is used, the peeling phenomenon of the transparent conductive film is about 1% or less in all the light emitting diode chips as in the first embodiment. It has been confirmed that the yield of manufacturing light emitting diodes can be significantly improved.
[0033]
(Third embodiment)
As a third embodiment of the present invention, a p-type (zinc-doped) AlGaInAs layer having a thickness of 10 nm is formed as a transparent conductive film separation preventing layer on a p-type GaP layer, and the Al composition contained in the AlGaInAs is respectively adjusted. A red light emitting diode having an emission wavelength of about 630 nm with 0.1, 0.4, and 0.8 was produced. The other configurations, the epitaxial growth method, the epitaxial structure, the method of forming the ITO film, and the like are the same as those of the first embodiment, and thus redundant description will be omitted.
[0034]
Further, the light emitting diode is formed by cutting the above-described epitaxial wafer including the p-type AlGaInAs layer into a chip having a chip size of 300 μm by dicing as in the first and second embodiments. In this step such as dicing, the transparent conductive film is cut while maintaining the adhesion to the p-type AlGaInAs layer. The cut light emitting diode is die-bonded on the TO-18 stem, and is electrically connected to the TO-18 stem by wire bonding.
[0035]
According to the light emitting diode of the third embodiment, even in the case where the AlGaInAs layer is used, the peeling phenomenon of the transparent conductive film is about 1% or less in all the light emitting diode chips as in the first embodiment. It has been confirmed that the yield of manufacturing light emitting diodes can be significantly improved.
[0036]
【The invention's effect】
As described above, according to the light emitting diode of the present invention, the semiconductor layer in contact with the transparent conductive film 7 is made of a compound semiconductor containing at least aluminum and has a concentration of 1 × 10 ¹⁹ cm ⁻³ or more. Since the film peeling prevention layer is provided, peeling of the transparent conductive film due to dicing or the like does not occur, light can be emitted at a low operating voltage, and high luminance can be realized.
[Brief description of the drawings]
FIG. 1 is a sectional view of a light emitting diode according to a first embodiment of the present invention.
FIG. 2 is a sectional view of a light emitting diode described in Patent Document 1.
[Explanation of symbols]
1. n-type GaAs substrate 2, (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P clad layer 3, (Al _0.15 Ga _0.85 ) _0.5 In _0.5 P active layer 4, p-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P clad layer 5, p-type GaP layer 6, p-type AIGaAs layer 6A, p-type InP compound semiconductor layer 7, transparent conductive film 8 , N-type electrode 9, p-type electrode 10, light emitting diode 20, light emitting diode

Claims (5)

A semiconductor substrate;
A light-emitting portion provided on the semiconductor substrate and having at least an active layer sandwiched between cladding layers of different conductivity types;
A transparent conductive film peeling prevention layer provided on the light emitting portion and made of a compound semiconductor containing at least aluminum and containing a conductivity type determining impurity having a concentration of 1 × 10 ¹⁹ cm ⁻³ or more;
A transparent conductive film made of a metal oxide provided on the transparent conductive film separation preventing layer,
A surface electrode provided on the transparent conductive film,
A light emitting diode having an electrode provided on the entire surface or a part of the back surface of the semiconductor substrate. The light emitting diode according to claim 1, wherein the transparent conductive film peeling prevention layer is formed with a thickness of 300 nm or less. The light emitting diode according to claim 1, wherein the transparent conductive film contains indium tin oxide. The light emitting diode according to claim 1, wherein the transparent conductive film peeling prevention layer is an arsenic compound containing at least aluminum. The light emitting _{portion, (Al X Ga 1-X} ) Y In 1-Y P (0 ≦ X ≦ 1,0 ≦ Y ≦ 1) according to claim 1, wherein the light-emitting diodes, characterized in that it consists of material.

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