JP2002246648A - Wavelength conversion type semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wavelength conversion type semiconductor device for improving the reflection factor of an electrode that functions as a reflection surface and at the same time reduces contact resistance. SOLUTION: The wavelength conversion type semiconductor device 10 contains a lower p-type layer 13 and an upper n-type layer 12 for composing a pn junction, a wavelength conversion material 17 that is provided at the upper portion, a first electrode 14 that is provided on the lower surface of the p-type layer and prevents excitation light from the pn junction that is electrically in contact with the p-type layer from being transmitted to the outside, and a second electrode 16 that surrounds the end face of the p-type layer and the n-type layer and is electrically in contact with only the n-type layer. The wavelength conversion type semiconductor device 10 is composed so that the second electrode can be composed of a high reflection factor metal layer 16a that is made of a material having a high reflection factor near the wavelength of excitation light from the pn junction and is as thick as 10 nm or more, and a conductive transparent oxide layer 16b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wavelength conversion type semiconductor device, and more particularly to an electrode structure having a high reflectance.

[0002]

2. Description of the Related Art Conventionally, for example, typical gallium nitride-based (In (y) Al (1-xy) Ga (x) N: x + y
.Ltoreq.1, 0.ltoreq.x.ltoreq.1, 0.ltoreq.y.ltoreq.1) A wavelength conversion type semiconductor device using a device is configured as shown in FIG. In FIG. 7, the wavelength conversion type semiconductor device 1 is configured as an n-type gallium nitride-based white LED, and has an n-type gallium nitride-based layer 3 and a p-type nitride layer sequentially stacked on the lower surface of the transparent substrate 2. A gallium-based layer 4, a p-type gallium nitride-based electrode 5 formed on the surface of the p-type gallium nitride-based layer 4, and an n-type gallium nitride-based layer 3 and a p-type nitride An insulating film 6 formed to cover the junction of the gallium-based layer 4, an n-type gallium nitride-based electrode 7 formed to cover the entire end surface around the n-type gallium nitride-based layer 3, And a wavelength conversion material 8 provided on the substrate 2.
a.

The transparent substrate 2 is made of a material which is transparent to excitation light, which will be described later, such as a sapphire C-plane substrate. The n-type gallium nitride-based layer 3 and the p-type gallium nitride-based layer 4 are formed by a film forming method such as MOCVD (metal organic chemical vapor deposition). These n-type gallium nitride-based layer 3 and p-type gallium nitride-based layer 4
After film formation, a peripheral end face is formed as shown in the figure by a dry etching method such as an RIE method (reactive ion etching method) using chlorine gas.

The p-type gallium nitride-based electrode 5 is an N-type electrode capable of making good electrical contact with the p-type gallium nitride-based layer 4.
It is made of a metal such as i or Rh. The insulating film 6
Are SiO ₂ and Al _{2 which are} not deteriorated by excitation light described later.
It is made of a transparent material such as O ₃ .

The n-type gallium nitride-based electrode 7 is made of Ti
/ Al laminated electrode. Further, the above n
The gallium nitride-based electrode 7 is formed so as to cover the end face of the chip so as not to emit the excitation light from the end faces (chip end faces) of the n-type gallium nitride based layer 3 and the p-type gallium nitride based layer 4. Thus, the n-type gallium nitride-based electrode 7 reflects the incident excitation light.

[0006] The p-type gallium nitride-based electrode 5 and the n-type gallium nitride-based electrode 7 are connected to the sub-electrode through bonding pads 5a, 7a and eutectic electrodes 5b, 7b of Au bump or Au-Sn alloy, respectively. It is mechanically fixed to the extraction electrodes 9a and 9b of the mount 9, and is electrically connected. The extraction electrodes 9a and 9b are
For example, generally, an Au wire 9c having a diameter of about 25 μm,
9d is drawn out to the outside by wire bonding.

The wavelength conversion material 8 is constituted by combining, for example, a YAG-based phosphor or a ZnS-based phosphor, and when excitation light is incident, generates fluorescence having a wavelength different from the excitation light. The light is emitted toward the outside.

The wavelength conversion type semiconductor device 1 having such a configuration
According to the method, the excitation light is generated at the junction between the n-type gallium nitride-based layer 3 and the p-type gallium nitride-based layer 4 by applying a drive voltage between the extraction electrodes 9a and 9b of the submount 9. Then, the excitation light is reflected by the inner surfaces of the p-type gallium nitride-based electrode 5 and the n-type gallium nitride-based electrode 7 and enters the transparent substrate 2 from the upper surface of the n-type gallium nitride-based layer 3. The excitation light transmitted through the transparent substrate 2 is incident on the wavelength conversion material 8, and the wavelength conversion material 8 generates light having a different wavelength by the incident excitation light and emits the light upward. In this manner, the wavelength conversion type semiconductor element 1 emits, for example, white light.

[0009]

By the way, in the wavelength conversion type semiconductor device 1 having such a configuration, the amount of light emitted from the wavelength conversion material 8 is smaller than the amount of excitation light incident on the wavelength conversion material 8. Dependent. Therefore, in order to increase the luminous efficiency of the wavelength conversion type semiconductor element 1, the light amount of the excitation light may be increased. For this reason, the end faces around the n-type gallium nitride-based layer 3 and the p-type gallium nitride-based layer 4 are inclined at an inclination angle of, for example, about 45 degrees ± 5 degrees as shown in the figure, so that the n-type gallium nitride-based electrode The excitation light reflected at 7 is guided toward the wavelength conversion material 8.

However, since the n-type gallium nitride-based electrode 7 has a relatively low reflectance with respect to the excitation light, the light incident on the n-type gallium nitride-based electrode 7 is Part of the light is absorbed by the n-type gallium nitride-based electrode 7 without being reflected. For this reason, the quantity of the excitation light incident on the wavelength conversion material 8 is reduced, and the luminous efficiency of the wavelength conversion type semiconductor element 1 is reduced, so that there is a problem that the characteristics of the device cannot be sufficiently brought out. . Further, since the contact resistance between the n-type gallium nitride-based electrode 7 and the n-type gallium nitride-based layer 3 is relatively large, the temperature increases due to Joule heat, and the characteristics of the electronic device deteriorate. There was a problem that would.

In view of the above, it is an object of the present invention to provide a wavelength conversion type semiconductor device in which the reflectance of an electrode functioning as a reflection surface is increased and the contact resistance is reduced. In the following, a description will be given of the most used wavelength conversion type semiconductor element.

[0012]

According to a first aspect of the present invention, the above object is provided on a lower p-type layer and an upper n-type layer constituting a pn junction, and on a lower surface of the p-type layer. In addition, the first electrode that does not transmit the excitation light from the pn junction electrically in contact with the p-type layer to the outside, and surrounds the end faces of the p-type layer and the n-type layer and electrically contacts only the n-type layer A second electrode, wherein the second electrode is a high-reflectivity metal layer having a thickness of 10 nm or more made of a material having high reflectivity in the vicinity of the wavelength of the excitation light from the pn junction. And a conductive transparent oxide layer.

According to a second aspect of the present invention, the above object is achieved by providing a lower p-type layer and an upper n-type layer constituting a pn junction, a wavelength conversion material disposed above these layers, A first electrode provided on the lower surface of the mold layer and not transmitting the excitation light from the pn junction electrically in contact with the p-type layer to the outside, and surrounding the end faces of the p-type layer and the n-type layer and n-type layer A second electrode electrically contacting only with the second electrode, wherein the second electrode is made of a material having a high reflectivity near the wavelength of the excitation light from the pn junction. This is achieved by a wavelength conversion type semiconductor device, which is constituted by a high reflectance metal layer having a thickness of 10 nm or more and a conductive transparent oxide layer.

According to a third aspect of the present invention, there is provided a semiconductor device comprising: a lower p-type gallium nitride-based layer (In (y) Al (1-xy) Ga (x) N: x + y
.Ltoreq.1,0.ltoreq.x.ltoreq.1,0.ltoreq.y.ltoreq.1) and an upper n-type gallium nitride-based layer, a wavelength converter disposed above these layers, and a lower surface of the p-type gallium nitride-based layer. A first electrode for p-type gallium nitride that does not transmit the excitation light from the pn junction electrically in contact with the p-type gallium nitride-based layer to the outside, and an end face of the p-type gallium nitride-based layer and a region of the pn junction. An insulating film surrounding the end face and being transparent in the vicinity of the wavelength of the excitation light from the pn junction; and an insulating film surrounding the end faces of the p-type gallium nitride-based layer and the n-type gallium nitride-based layer and having only the n-type gallium nitride-based layer. A second electrode for an n-type gallium nitride system in electrical contact, wherein the second electrode has a reflectivity near the wavelength of the excitation light from the pn junction. A high-reflectivity metal layer having a thickness of 10 nm or more made of a high- Characterized in that it is composed of the oxide layer, by the wavelength conversion-type semiconductor device is achieved.

[0015] In the wavelength conversion type semiconductor device according to the present invention, the end faces around the p-type gallium nitride-based layer and the n-type gallium nitride-based layer are preferably inclined vertically or downward.

In the wavelength conversion type semiconductor device according to the present invention, preferably, the conductive transparent oxide layer has a thickness of 5 μm or less.

In the wavelength conversion type semiconductor device according to the present invention, preferably, the conductive transparent oxide layer is made of zinc oxide, indium oxide, tin oxide or a compound mainly containing these oxides.

In the wavelength conversion type semiconductor device according to the present invention, preferably, when the thickness d of the conductive transparent oxide layer is n, the refractive index of the conductive oxide layer is n, and the wavelength of the excitation light is λ,
d = mλ / n (where m is an integer).

In the wavelength conversion type semiconductor device according to the present invention, the high reflectivity metal layer is preferably made of Ag, Rh or an alloy film or a laminated film containing these metals.

The wavelength conversion type semiconductor device according to the present invention is preferably such that a metal single layer film, a laminated film, an alloy film or a conductive transparent oxide film is provided between the conductive transparent oxide layer and the high-reflectance metal layer. And an intermediate electrode layer made of

In the wavelength conversion type semiconductor device according to the present invention, preferably, the wavelength conversion type semiconductor device is a white LED, and the first electrode is a p-type gallium nitride based ohmic electrode.

According to the second configuration, by applying a drive voltage between the first electrode and the second electrode, excitation light is generated at a pn junction between the n-type layer and the p-type layer. I do. Then, part of the excitation light is reflected by the inner surfaces of the first electrode and the second electrode, and the other part directly enters the wavelength conversion material from the upper surface of the n-type layer. Then, the excitation light is incident on the wavelength conversion material, and the wavelength conversion material generates light having a different wavelength by the incident excitation light and emits the light upward.

In this case, since the second electrode includes the high-reflectance metal layer, the amount of excitation light reflected by the second electrode increases, and the excitation light is incident on the wavelength conversion material. The amount of light will increase. Accordingly, the amount of light emitted from the wavelength conversion material also increases, so that the luminous efficiency of the wavelength conversion type semiconductor device is improved. If the thickness of the high-reflectance metal layer is 10 nm or less, the reflectance will decrease, and the amount of excitation light incident on the wavelength conversion material will also decrease.

Further, since the second electrode includes the conductive transparent oxide layer, the conductive transparent oxide layer has good electrical contact with the n-type gallium nitride-based layer. The contact resistivity of the second electrode will be reduced, the driving voltage applied between the first electrode and the second electrode may be low, and a power-saving semiconductor element will be obtained, Since the calorific value is reduced, it is possible to suppress the deterioration of the characteristics of the semiconductor element due to heat. In addition, since the conductive transparent oxide layer is transparent, the excitation light is transmitted at a high transmittance without absorbing the excitation light,
The reflection efficiency by the second electrode is improved.

According to the third configuration, by applying a drive voltage between the first electrode and the second electrode, a pn junction between the n-type gallium nitride-based layer and the p-type gallium nitride-based layer is formed. As a result, excitation light is generated. Then, a part of the excitation light is reflected by the inner surfaces of the first electrode and the second electrode,
Another part directly enters the wavelength conversion material from the upper surface of the n-type gallium nitride-based layer. Then, the excitation light is incident on the wavelength conversion material, and the wavelength conversion material generates light having a different wavelength by the incident excitation light and emits the light upward.

In this case, since the second electrode includes the high-reflectance metal layer, the amount of excitation light reflected by the second electrode increases, and the excitation light is incident on the wavelength conversion material. The amount of light will increase. Accordingly, the amount of light emitted from the wavelength conversion material also increases, so that the luminous efficiency of the n-type gallium nitride-based wavelength conversion type semiconductor device is improved. If the thickness of the high-reflectance metal layer is 10 nm or less, the reflectance will decrease, and the amount of excitation light incident on the wavelength conversion material will also decrease.

Further, since the second electrode includes the conductive transparent oxide layer, the conductive transparent oxide layer has good electrical contact with the n-type gallium nitride-based layer. The contact resistivity of the second electrode will be reduced, the driving voltage applied between the first electrode and the second electrode may be low, and a power-saving semiconductor element will be obtained, Since the calorific value is reduced, the deterioration of the characteristics of the semiconductor element due to heat can be suppressed, and the separation of the second electrode from the n-type gallium nitride-based layer is suppressed. Will be improved. Also,
Since the conductive transparent oxide layer is transparent, the excitation light is transmitted at a high transmittance without absorbing the excitation light, so that the reflection efficiency by the second electrode is improved.

When the peripheral end faces of the p-type gallium nitride-based layer and the n-type gallium nitride-based layer are vertically or inclined downward, the p-type gallium nitride-based layer and the n-type The contact area with the gallium nitride-based layer will increase, and the adhesion of the second electrode will improve, and the excitation light reflected by the second electrode will be reflected upward. As a result, the efficiency of extracting the excitation light is improved.

When the conductive transparent oxide layer has a thickness of 5 μm or less, the absorption of excitation light by the conductive transparent oxide layer is further suppressed, so that the second electrode, that is, a high reflectance The reflection efficiency of the excitation light by the metal layer is improved.

When the conductive transparent oxide layer is made of zinc oxide, indium oxide, tin oxide or a compound containing these oxides as a main material, the above-mentioned contact resistivity is low. The driving voltage applied between the first electrode and the second electrode may be low.

The thickness d of the conductive transparent oxide layer is d = mλ / n (where m is an integer), where n is the refractive index of the conductive oxide layer and λ is the wavelength of the excitation light. in case of,
Interference between the conductive transparent oxide layer and the high reflectance metal layer is avoided, and the reflectance of the excitation light by the high reflectance metal layer is maximized.

When the high reflectivity metal layer is made of Ag, Rh or an alloy film or a laminated film containing these metals, each of these materials has a reflectivity of 50% or more at a wavelength of 370 nm or more. Therefore, the second electrode having a high reflectance can be obtained.

In the case where an intermediate electrode layer made of a metal single layer film, a laminated film, an alloy film or a conductive transparent oxide film is provided between the conductive transparent oxide layer and the high reflectance metal layer,
Electrode peeling between the conductive transparent oxide layer and the high-reflectance metal layer is suppressed.

In the case where the wavelength conversion type semiconductor element is a white LED and the first electrode is a p-type gallium nitride based ohmic electrode, the first electrode further contacts the p-type gallium nitride based layer. The resistivity is reduced, and brighter white light can be extracted.

[0035]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to FIGS. still,
Since the embodiments described below are preferred specific examples of the present invention, various technically preferred limitations are added.
The scope of the present invention is not limited to these embodiments unless otherwise specified in the following description.

FIG. 1 shows the configuration of an embodiment of the wavelength conversion type semiconductor device according to the present invention. In FIG. 1, a wavelength conversion type semiconductor device 10 is a white LED as an n-type gallium nitride-based wavelength conversion type semiconductor device, and is an n-type gallium nitride-based layer sequentially laminated on the lower surface of a transparent substrate 11. (In (y) Al (1-xy) Ga (x) N:
x + y ≦ 1, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1) 12, a p-type gallium nitride-based layer 13, a p-type gallium nitride-based electrode 14 formed on the surface of the p-type gallium nitride-based layer 13, This p
An insulating film 15 formed so as to cover from the n-type gallium nitride-based electrode 14 to the junction between the n-type gallium nitride-based layer 12 and the p-type gallium nitride-based layer 13, and an end face around the n-type gallium nitride-based layer 12 It includes an n-type gallium nitride-based electrode 16 formed so as to cover the entirety, and a wavelength conversion material 17 provided on the transparent substrate 11, and is configured by being entirely covered by a mold resin 18. ing.

The transparent substrate 11 is made of, for example, sapphire C
It is made of a material that is transparent to excitation light described below, such as a surface substrate. The n-type gallium nitride-based layer 12 and p
The gallium nitride-based layer 13 is formed on the transparent substrate 11 by a film forming method such as MOCVD (metal organic chemical vapor deposition).
Are sequentially formed on the lower surface of the substrate.

The n-type gallium nitride based layer 12 and p
The gallium nitride-based layer 13 is formed such that the peripheral end faces are inclined as shown in the figure by dry etching such as RIE (reactive ion etching) using chlorine gas, for example, after film formation. Accordingly, the contact area of the insulating film 15 with the n-type gallium nitride-based layer 12 and the p-type gallium nitride-based layer 13 is increased, so that the adhesion of the insulating film 15 is improved, and the reliability at the time of forming the insulating film 15 is improved. And the peeling of the insulating film 15 is suppressed. Therefore, the reliability of the electrical insulation between the n-type gallium nitride-based layer 12 and the p-type gallium nitride-based layer 13 is improved, and the yield of a so-called excitation light source element is improved. Further, due to the inclination of the end faces around the n-type gallium nitride-based layer 12 and the p-type gallium nitride-based layer 13, the excitation light is reflected by the second electrode 16 described later toward the upper transparent substrate,
The efficiency of light incidence on the wavelength conversion material 17 is improved.
In addition, the inclination angle of the end face around the n-type gallium nitride-based layer 12 and the p-type gallium nitride-based layer 13 may be 90 degrees or less from the viewpoint of the adhesion of the insulating film 15, and from the viewpoint of the reflection efficiency. Is preferably set to 45 degrees ± 5 degrees.

The p-type gallium nitride-based electrode 14
It is made of a metal such as Ni or Rh that can make good electrical contact with the type gallium nitride-based layer 13. The insulating film 15 is made of SiO ₂ , A which is not deteriorated by excitation light described later.
It is made of a transparent material such as l ₂ O ₃ .

The n-type gallium nitride-based electrode 16 is formed of n
-Type gallium nitride-based layer 12 and p-type gallium nitride-based layer 13
Is formed so as to cover the chip end face so as not to emit the excitation light from the end face (chip end face). Thus, the n-type gallium nitride-based electrode 16 reflects incident excitation light.

The p-type gallium nitride-based electrode 14 and n
The gallium nitride-based electrode 16 is connected to the extraction electrodes 19a, Mechanically fixed to 19b,
Electrically connected. The extraction electrodes 19a, 19
b is pulled out to the outside by wire bonding using, for example, Au wires 19c and 19d generally having a diameter of about 25 μm.

The wavelength conversion material 17 is constituted by combining, for example, a YAG-based phosphor or a ZnS-based phosphor, and when excitation light is incident, generates fluorescence having a wavelength different from the excitation light. The light is emitted toward the outside.

The above configuration is substantially the same as that of the conventional wavelength conversion type semiconductor device 1 shown in FIG. 7, but in the wavelength conversion type semiconductor device 10 according to the embodiment of the present invention, the second electrode 16 However, the configuration is different from that shown in FIG. That is, in FIG. 2, the second electrode 16 is an n-gallium nitride-based electrode, and includes a high-reflectance metal layer 16a, a conductive transparent oxide layer 16b,
It is composed of

The high reflectivity metal layer 16a is made of a material having a high reflectivity of, for example, 50% or more at a wavelength of 370 nm or more, which is the wavelength of the excitation light from the pn junction, for example, Ag, R
h or an alloy film or a laminated film containing these metals. Although Al also has a high reflectance, it has been confirmed that contact resistance greatly increases when an Al electrode is formed on the conductive transparent oxide layer 16b and heated to 400 ° C. or higher. It is not suitable as a material for the reflectance metal layer 16a. The material of the high-reflectance metal layer 16a is an alloy layer or a laminated film composed of the above-mentioned high-reflectivity metals Ag and Rh and other metals having no high-reflectance, such as Pd, Pt, Cu, and Ni. You may. Further, the high-reflectivity metal layer 16a is formed such that the excitation light is
Is not less than 10 nm, preferably 100 nm to obtain sufficient reflected light.
Selected above.

The conductive transparent oxide layer 16b may be a generally known conductive transparent oxide film, for example, zinc oxide, indium oxide, tin oxide or their oxides as a main material. It is composed of a compound, for example, In-Sn-O or the like. The conductive transparent oxide layer 16b is preferably formed by an ion plating method, a sputtering method, an electron beam evaporation method, a laser ablation method, or the like. In particular, according to the ion plating method using arc discharge, a high-quality film can be manufactured at room temperature, so that easy lift-off patterning is possible.

Further, the thickness of the conductive transparent oxide layer 16b is preferably set to increase the reflection efficiency of the highly reflective metal layer 16a, that is, to increase the light transmittance of the conductive transparent oxide layer 16b itself. The thickness is selected to be 5 μm or less, and particularly to obtain a high reflectance of 60% or more, the thickness is selected to be 1 μm or less. By the way, when the thickness of the conductive transparent oxide layer 16b is 1 μm or less, the conductive transparent oxide layer 16b has a thickness of about the wavelength of the excitation light.
The reflectance of the second electrode 16 is reduced due to the interference of the excitation light within 6b. In order to avoid this, the film thickness d may be set so that the reflectance is maximized by the interference. When the refractive index of the conductive transparent oxide layer 16b is n and the wavelength of the excitation light is λ, the film thickness d at which the reflectance becomes maximum is given by d = mλ / n.

On the other hand, the n-type gallium nitride-based layer 12
A structure for suppressing interference of excitation light in the conductive transparent oxide layer 16b may be provided to one or both of the metal thin film layer 16a and the high-reflectance metal thin film layer 16a. Specifically, at least one of the n-type gallium nitride-based layer 12 and the high-reflectance metal thin film layer 16a has a size of 1 nm to 1 nm.
It can be obtained by forming irregularities of about μm.

Further, an intermediate electrode layer (not shown) is preferably formed between the high-reflectance metal layer 16a and the conductive transparent oxide layer 16b in order to suppress electrode peeling. This intermediate electrode layer is made of a material that does not impair the reflection efficiency of the high-reflectance metal layer 16a, for example, a metal single-layer film such as Ni or Ti, a laminated film, an alloy film, or a conductive transparent oxide film.

The high-reflectance metal layer 16a, the conductive transparent oxide layer 16b and the intermediate electrode layer are preferably formed by electron beam evaporation or sputtering, and are used to prevent electrode peeling and improve electrical characteristics. For this purpose, an alloying process may be performed after the formation, or a laminated film may be formed by the alloying process. Further, the high reflectance metal layer 16
The patterning of the conductive transparent oxide layer 16b and the intermediate electrode layer is performed by a general method, for example, an etching method or a lift-off method.

The wavelength conversion type semiconductor device 10 according to the embodiment of the present invention is configured as described above. By applying a drive voltage between the extraction electrodes 19 a and 19 b of the submount 19, the n-type gallium nitride-based layer is formed. Excitation light is generated at the pn junction between the p-type gallium nitride-based layer 13 and the p-type gallium nitride-based layer 13, and the excitation light is applied to the first electrode 14 and the second electrode 16.
And is incident on the transparent substrate 11 from the upper surface of the n-type gallium nitride-based layer 12. The excitation light transmitted through the transparent substrate 11 is incident on the wavelength conversion material 17, and the wavelength conversion material 17 generates light of different wavelengths by the incident excitation light and emits the light upward. Thus, the wavelength conversion type semiconductor element 10 emits, for example, white light.

In this case, since the second electrode 16 includes the high-reflectance metal layer 16a having, for example, a reflectance of 50% or more, the amount of excitation light reflected by the second electrode 16 increases. And the amount of excitation light incident on the wavelength conversion material 17 increases. Therefore, the wavelength conversion material 1
7, the light emitting efficiency of the n-type gallium nitride-based wavelength conversion type semiconductor element 10 is improved.

Further, since the second electrode 16 includes the conductive transparent oxide layer 16b, the conductive transparent oxide layer 16b has good electrical contact with the n-type gallium nitride-based layer 12. Therefore, the contact resistivity of the second electrode 12 to the n-type gallium nitride-based layer 12 is reduced. Therefore, the first electrode 14 and the second electrode 1
The drive voltage applied between the electrodes 6 can be low, and a power-saving semiconductor element can be obtained. In addition, a decrease in the amount of heat generated can suppress a decrease in the characteristics of the semiconductor element due to heat.

Further, since the peripheral end faces of the p-type gallium nitride-based layer 13 and the n-type gallium nitride-based layer 12 are inclined downward, the p-type gallium nitride-based layer 13 of the second electrode 16 is formed. Also, the contact area of the second electrode 16 with the n-type gallium nitride-based layer 12 and the insulating film 15 increases, so that the adhesion of the second electrode 16 is improved and the excitation light reflected by the second electrode is reduced. Since the light is reflected upward, the extraction efficiency of the excitation light is improved.

Here, various characteristics of the second electrode 16 will be verified. For this verification, a sample electrode 20 shown in FIG. 3 was manufactured. This sample electrode 20 has, for example, n to
An electrode 22 having the same configuration as the above-described second electrode 16 is formed by continuously forming a film on the n-type gallium nitride-based layer 21 having a carrier density of 5 × 10 ¹⁸ / cm ³ by using an electron beam evaporation device. That is, the conductive transparent oxide layer 23 and the high-reflectance metal layer 24 were sequentially formed and patterned by the lift-off method, and no heat treatment was performed. The conductive transparent oxide layer 23 has the same configuration as the above-described conductive transparent oxide layer 16b, and is formed of, for example, a 150-nm-thick zinc oxide film. The high-reflectivity metal layer 24 has the same configuration as the high-reflectivity metal layer 16a described above, and is formed by stacking, for example, a 0.3-nm-thick Ni film and a 300-nm-thick Ag film. I have. For comparison, a film thickness of 25 n, which is conventionally generally used, is formed on the same n-type gallium nitride-based layer 21.
A reference electrode formed with a m-thick Ti film and a 1 μm-thick film was also prepared. After patterning of the electrode, a heat treatment was performed at 500 ° C. for 20 seconds in a nitrogen atmosphere. Each of the above film thicknesses is a value of a film thickness monitor during film formation. Here, the electrode patterns of the sample electrode 20 and the reference electrode are formed in an annular shape as shown in FIG.

A drive voltage was applied to the sample electrode 20 and the reference electrode by the drive power supply 25, and the current-voltage characteristics were measured.
A characteristic curve as shown in the graph of FIG. 5 was obtained. As a result, it was confirmed that the current-voltage characteristics of both the sample electrode 20 and the reference electrode were substantially equal.

Next, the reflectances of the sample electrode 20 and the reference electrode were measured. In the measurement of the reflectance, both electrodes were formed on a quartz substrate having a thickness of 1 mm without patterning, and the reflectance was measured by irradiating light from the quartz substrate side (in this case, Both electrodes were not subjected to the alloying treatment described above.) However, reflection spectrum characteristics as shown in the graph of FIG. 6 were obtained. As a result, the reference electrode has a reflectance of 40% at a wavelength of 370 nm or more, whereas the sample electrode 20 has a reflectance of about 70% at a wavelength of 370 nm or more, and has a reflectance of 50% or more. .

Further, white LEDs were manufactured as the wavelength conversion type semiconductor device 10 and the conventional wavelength conversion type semiconductor device 1 shown in FIG. 7, respectively, and their relative total luminous fluxes were compared. As each white LED, a p-type and an n-type gallium nitride-based layer are sequentially formed on a sapphire substrate by MOCVD to produce a gallium nitride-based ultraviolet LED as a so-called excitation light source element, and a chlorine-based gas is used. The n-type gallium nitride-based layer was exposed by etching about 400 nm from the surface of the p-type and n-type gallium nitride-based layers by RIE. A Rh film of about 300 nm is formed as the first electrode 14, and a Rh film of about 400 nm is formed as the insulating film 15.
Then, an electrode having the same structure as the sample electrode 20 or the reference electrode is formed as a second electrode 16 on the end face of the chip, and Ti and A
Mounting bonding pad made of u and Au-S
A eutectic electrode made of an n alloy was formed. Here, all the electrodes and the insulating films were formed by the electron beam evaporation method, and were patterned by the lift-off method. Finally, in a state where all the electrodes are formed, each chip is separated by a so-called scribing method, and each chip is die-bonded to a submount, and an oxide insulating film that reflects ultraviolet light and transmits visible light. A white LED was manufactured by placing a wavelength conversion material composed of a phosphor and a phosphor on a sapphire substrate and sealing it with a mold resin.

With respect to the white LED as the wavelength conversion type semiconductor device according to the embodiment of the present invention and the conventional white LED, the white light obtained by driving with a driving current of 20 mA DC is integrated by an integrating sphere. When the total luminous flux was measured, assuming that the total luminous flux of the conventional white LED was 100, the total luminous flux of the white LED according to the embodiment of the present invention was 172.
It was confirmed that the relative total luminous flux increased significantly.

[0059]

As described above, according to the present invention, since the second electrode includes the high-reflectance metal layer,
The amount of excitation light reflected by the second electrode increases, and the amount of excitation light incident on the wavelength conversion material increases. Accordingly, the amount of light emitted from the wavelength conversion material also increases, so that the luminous efficiency of the wavelength conversion type semiconductor device is improved.

Further, since the second electrode includes the conductive transparent oxide layer, the conductive transparent oxide layer has good electrical contact with the n-type gallium nitride-based layer. The contact resistivity of the second electrode will be reduced, the driving voltage applied between the first electrode and the second electrode may be low, and a power-saving semiconductor element will be obtained, Since the calorific value is reduced, it is possible to suppress the deterioration of the characteristics of the semiconductor element due to heat. As described above, according to the present invention, it is possible to provide an extremely excellent wavelength conversion type semiconductor device in which the reflectance of the electrode functioning as the reflection surface is increased and the contact resistance is reduced.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing one embodiment of a wavelength conversion type semiconductor device according to the present invention.

FIG. 2 is a partially enlarged cross-sectional view showing a configuration of a second electrode in the wavelength conversion type semiconductor device of FIG.

FIG. 3 is a schematic sectional view showing a configuration of a sample electrode for verifying a second electrode in the wavelength conversion type semiconductor device of FIG.

FIG. 4 is a schematic plan view showing an electrode pattern of the sample electrode of FIG.

FIG. 5 is a graph showing current-voltage characteristics of the sample electrode and the reference electrode of FIG.

FIG. 6 is a graph showing reflection spectrum characteristics of the sample electrode and the reference electrode of FIG.

FIG. 7 is a schematic cross-sectional view showing a configuration of an example of a conventional wavelength conversion type semiconductor device.

[Explanation of symbols]

 Reference Signs List 10 wavelength conversion type semiconductor element 11 transparent substrate 12 n-type gallium nitride-based layer 13 p-type gallium nitride-based layer 14 p-type gallium nitride-based electrode 14a bonding pad 14b eutectic electrode 15 insulating film 16 n-type gallium nitride-based electrode 16a High reflectivity metal layer 16b Conductive transparent oxide layer 16c Bonding pad 16d Eutectic electrode 17 Wavelength conversion material 18 Mold resin 19 Submount 20 Sample electrode 21 n-type gallium nitride based layer 21 22 Electrode 23 Conductive transparent oxide layer 24 High reflectivity metal layer 25 Drive power supply

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masahiko Tsuchiya 2-9-13 Stanley, Nakameguro, Meguro-ku, Tokyo Inside Electric Co., Ltd. (72) Hiroshi Hirasawa 2-9-13 Stanley, Nakameguro, Meguro-ku, Tokyo − Within Electric Co., Ltd. (72) Inventor Toshio Tomiyoshi 2-9-13 Stanley, Nakameguro, Meguro-ku, Tokyo − F-term within Electric Co., Ltd. (reference) 4M104 AA04 AA09 BB04 BB05 BB08 BB36 CC01 CC03 DD34 DD35 DD36 DD37 DD68 DD78 DD83 EE05 FF13 GG04 HH09 HH20 5F041 AA14 CA02 CA34 CA65 CA74 CA76 CA82 CA88 CA92 CA93 CA98 CB15 DA07 DA12 DA20 DA43 DB09 EE25

Claims (10)

[Claims] An excitation light from a pn junction provided on a lower surface of a lower p-type layer and an upper n-type layer and electrically contacting the p-type layer and constituting a pn junction is externally provided. A semiconductor element comprising: a first electrode that does not transmit light; and a second electrode that surrounds end faces of the p-type layer and the n-type layer and is in electrical contact with only the n-type layer. Comprises a high-reflectivity metal layer having a thickness of 10 nm or more made of a material having a high reflectivity in the vicinity of the wavelength of the excitation light from the pn junction, and a conductive transparent oxide layer. , Semiconductor elements. 2. A lower p-type layer and an upper n-type layer constituting a pn junction, a wavelength conversion material disposed above the p-type layer and an upper n-type layer. A first electrode that does not transmit the excitation light from the pn junction that has come into contact with the outside, a second electrode that surrounds the end faces of the p-type layer and the n-type layer, and is electrically contacted only with the n-type layer, Wherein the second electrode has a high reflectivity metal layer having a thickness of 10 nm or more made of a material having a high reflectivity in the vicinity of the wavelength of the excitation light from the pn junction; A wavelength conversion type semiconductor device, comprising: a transparent oxide layer. 3. A lower p-type gallium nitride based layer (In (y) Al (1-xy) Ga (x) constituting a pn junction
N: x + y ≦ 1, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1) and the upper n-type gallium nitride-based layer, the wavelength converter disposed above these layers, and the lower surface of the p-type gallium nitride-based layer A first electrode for p-type gallium nitride that does not allow externally transmitting excitation light from a pn junction electrically connected to the p-type gallium nitride-based layer, an end face of the p-type gallium nitride-based layer, and a pn junction An insulating film that surrounds the end face of the region and is transparent in the vicinity of the wavelength of the excitation light from the pn junction, and that surrounds the end faces of the p-type gallium nitride-based layer and the n-type gallium nitride-based layer and that the n-type gallium nitride-based A second electrode for an n-type gallium nitride system electrically contacting only the layer, wherein the second electrode is located near the wavelength of the excitation light from the pn junction. A high-reflectivity metal layer having a thickness of 10 nm or more and made of a material having a high reflectivity; And a conductive transparent oxide layer. 4. The wavelength conversion type semiconductor according to claim 3, wherein the end faces around the p-type gallium nitride-based layer and the n-type gallium nitride-based layer are vertically or downwardly inclined. element. 5. The conductive transparent oxide layer has a thickness of 5 μm.
The wavelength conversion type semiconductor device according to claim 2, wherein: 6. The conductive transparent oxide layer comprises zinc oxide,
Characterized by being composed of indium oxide, tin oxide or a compound in which these oxides are a main material,
The wavelength conversion type semiconductor device according to claim 3. 7. When the thickness d of the conductive transparent oxide layer is n, the refractive index of the conductive oxide layer is n, and the wavelength of the excitation light is λ, d = mλ / n (where m is an integer). The wavelength conversion type semiconductor device according to any one of claims 3 to 6, wherein 8. The wavelength according to claim 3, wherein the high reflectivity metal layer is made of Ag, Rh, or an alloy film or a laminated film containing these metals. Conversion type semiconductor element. 9. An intermediate electrode layer comprising a metal single-layer film, a laminated film, an alloy film or a conductive transparent oxide film is provided between the conductive transparent oxide layer and the high-reflectance metal layer. The wavelength conversion type semiconductor device according to any one of claims 3 to 8, characterized in that: 10. The wavelength conversion type semiconductor device is a white LED, and the first electrode is a p-type gallium nitride based ohmic electrode. Wavelength conversion type semiconductor device.