JP7328558B2 - Light-emitting element and method for manufacturing light-emitting element - Google Patents

Description

The present invention relates to a light-emitting device and a method for manufacturing a light-emitting device.

2. Description of the Related Art In recent years, the development of light-emitting elements that emit ultraviolet light has been vigorously pursued. For example, Patent Document 1 discloses a light emitting device having a multiple quantum well structure suitable for emitting ultraviolet light.

JP-A-9-153645

Such a light-emitting device having a multiple quantum well structure and emitting ultraviolet light is being improved so as to have a higher emission output, but there is still room for improvement.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a light-emitting device that has a multiple quantum well structure and emits ultraviolet light with a high light output, and a method for manufacturing the light-emitting device.

The light emitting device according to the present invention is
an n-side nitride semiconductor layer;
an active layer emitting ultraviolet light, comprising a plurality of well layers made of a nitride semiconductor provided on the n-side nitride semiconductor layer, and a plurality of barrier layers made of a nitride semiconductor;
a p-side nitride semiconductor layer provided on the active layer;
At least one of the plurality of barrier layers includes, in order from the n-side nitride semiconductor layer side, a first barrier layer containing Al and Ga, and provided in contact with the first barrier layer, Al, a second barrier layer containing Ga and In and having a lower bandgap energy than the first barrier layer;
At least one of the plurality of well layers is provided in contact with the second barrier layer and has a lower bandgap energy than the second barrier layer.

Further, the method for manufacturing a light-emitting device according to the present invention includes:
an n-side nitride semiconductor layer growing step for growing an n-side nitride semiconductor layer; a plurality of well layers made of a nitride semiconductor on the n-side nitride semiconductor layer; and a plurality of barrier layers made of a nitride semiconductor. and a p-side nitride semiconductor layer growing step of growing a p-side nitride semiconductor layer on the active layer. a method,
The active layer growing step includes:
a first barrier layer growing step of growing a first barrier layer using a source gas containing an Al source gas, a Ga source gas, and an N source gas;
a second barrier layer growing step of growing a second barrier layer on the first barrier layer by using a source gas containing an Al source gas, a Ga source gas, an In source gas, and an N source gas;
a well layer growing step of growing a well layer having a bandgap energy smaller than that of the second barrier layer on the second barrier layer using a raw material gas containing a Ga raw material gas and an N raw material gas;
including.

A light-emitting device and a method for manufacturing a light-emitting device according to an embodiment of the present invention provide a light-emitting device that has a multiple quantum well structure and emits ultraviolet light with a high emission output, and a method for manufacturing the light-emitting device. can be done.

1 is a cross-sectional view showing the configuration of a light-emitting device according to one embodiment of the present invention; FIG. 2 is a diagram showing the structure of a semiconductor laminate of the light emitting device shown in FIG. 1; FIG. FIG. 3 is a diagram showing the bandgap energy of the structure of the semiconductor laminate shown in FIG. 2; 3 is a diagram showing another structure of the semiconductor laminate of the light emitting device shown in FIG. 1; FIG. 3 is a diagram showing another structure of the semiconductor laminate of the light emitting device shown in FIG. 1; FIG. FIG. 4 is a cross-sectional view when forming an n-side nitride semiconductor layer on the upper surface of the prepared first substrate in the method for manufacturing a light emitting device according to one embodiment of the present invention; FIG. 4 is a cross-sectional view when forming a first barrier layer on the n-side nitride semiconductor layer formed on the upper surface of the first substrate in the method for manufacturing a light emitting device according to one embodiment of the present invention; FIG. 4 is a cross-sectional view when forming a second barrier layer on the n-side nitride semiconductor layer formed on the upper surface of the first substrate in the method for manufacturing a light emitting device according to one embodiment of the present invention; FIG. 4 is a cross-sectional view when a well layer is formed on the n-side nitride semiconductor layer formed on the upper surface of the first substrate in the method for manufacturing a light emitting device according to one embodiment of the present invention; Cross section of a first wafer in which a p-side nitride semiconductor layer is formed on an active layer formed on an upper surface of a first substrate with an n-side nitride semiconductor layer interposed therebetween, in the method for manufacturing a light emitting device according to an embodiment of the present invention. It is a diagram. FIG. 4 is a cross-sectional view when forming a second electrode having a predetermined shape on the p-side nitride semiconductor layer of the first wafer in the method for manufacturing a light emitting device according to one embodiment of the present invention; FIG. 4 is a cross-sectional view when an insulating film and a metal layer are formed on the p-side nitride semiconductor layer of the first wafer on which the second electrode is formed in the method for manufacturing a light emitting device according to one embodiment of the present invention; FIG. 4 is a cross-sectional view when a second substrate having a metal layer formed on one surface thereof is prepared and the first wafer and the second substrate are opposed to each other in the method for manufacturing a light emitting device according to one embodiment of the present invention. FIG. 4 is a cross-sectional view of a second wafer produced in the method for manufacturing a light emitting device according to one embodiment of the present invention; FIG. 5 is a cross-sectional view when forming a first electrode with a predetermined pattern on the n-side nitride semiconductor layer of the second wafer in the method for manufacturing a light emitting device according to one embodiment of the present invention;

Hereinafter, embodiments and examples for carrying out the present invention will be described with reference to the drawings. Note that the light-emitting device and the method for manufacturing the light-emitting device described below are for embodying the technical idea of the present invention, and the present invention is not limited to the following unless otherwise specified.
In each drawing, members having the same function may be given the same reference numerals. In consideration of the explanation of the main points or the ease of understanding, the embodiments and examples may be divided for convenience, but the configurations shown in different embodiments and examples can be partially replaced or combined. In the embodiments and examples described later, descriptions of matters common to those described above will be omitted, and only differences will be described. In particular, similar actions and effects due to similar configurations will not be referred to successively for each embodiment or example. The sizes and positional relationships of members shown in each drawing may be exaggerated for clarity of explanation.

A semiconductor laminate used for a light-emitting element such as a light-emitting diode using a nitride semiconductor includes an n-side nitride semiconductor layer, a p-side nitride semiconductor layer, and between the n-side nitride semiconductor and the p-side nitride semiconductor. and an active layer provided. For the active layer, for example, a multiple quantum well structure including a plurality of well layers and a plurality of barrier layers is used, and a light emitting device that emits blue light uses, for example, a well layer made of InGaN. Further, even a light-emitting element that emits ultraviolet light can be configured using a well layer made of InGaN with a low In content when the emission wavelength is relatively long. A barrier layer made of AlGaN can be used in a light-emitting device that emits ultraviolet light.

However, in the process of various investigations by the present inventors, the active layer alternately including well layers made of InGaN and barrier layers made of AlGaN has a large lattice constant difference between the well layers and the barrier layers. It was found that lattice relaxation is likely to occur, and the surface roughness of the well layer and the barrier layer tends to increase. The inventor of the present invention thought that these factors might reduce the recombination probability in the active layer. Therefore, in order to reduce the lattice constant difference between the well layer and the barrier layer and to reduce the surface roughness of the barrier layer, an attempt was made to employ AlInGaN as the barrier layer. However, an active layer using a well layer made of InGaN and a barrier layer made of AlInGaN can reduce the lattice constant difference between the well layer and the barrier layer, reduce the surface roughness of the barrier layer, and crystallize the well layer. However, the recombination probability in the active layer hardly changed.

The inventor believes that the reason why the recombination probability of electrons and holes in the active layer hardly changes is that the difference between the bandgap energy of the well layer and the bandgap energy of the barrier layer is reduced by containing In in the barrier layer. I assumed it was because it was smaller. In other words, although the difference in lattice constant between the well layer and the barrier layer can be reduced, the confinement effect of electrons in the well layer is reduced, making it difficult for recombination to occur in the active layer. Therefore, in addition to a barrier layer (second barrier layer) containing Al, Ga, and In, the inventors proposed a barrier layer containing Al and Ga, which has a bandgap energy greater than that of the second barrier layer. A layer (first barrier layer) was arranged on the n-side nitride semiconductor layer side of the second barrier layer. As a result, the recombination probability could be improved and a light-emitting element exhibiting high light emission output could be obtained as compared with a light-emitting element not provided with the first barrier layer.

A light emitting device according to the present invention has been made based on the above findings, and includes an n-side nitride semiconductor layer, a plurality of well layers made of a nitride semiconductor provided on the n-side nitride semiconductor layer, An active layer that emits ultraviolet light and includes a plurality of barrier layers made of a nitride semiconductor; and a p-side nitride semiconductor layer provided on the active layer, wherein at least one of the plurality of barrier layers is a barrier. The layers are, in order from the n-side nitride semiconductor layer side, provided in contact with a first barrier layer containing Al and Ga and the first barrier layer, containing Al, Ga, and In, and having a bandgap energy higher than that of the first barrier layer. At least one well layer among the plurality of well layers is provided in contact with the second barrier layer and has a lower bandgap energy than the second barrier layer.

Embodiment Hereinafter, a light-emitting device of this embodiment and a method for manufacturing the light-emitting device will be described with reference to the drawings.

1. 1. Light Emitting Element FIG. 1 is a cross-sectional view showing the configuration of a light emitting element 10 according to this embodiment.

As shown in FIG. 1, the light emitting device 10 according to the present embodiment includes a second substrate 22, a metal layer 40 arranged on the second substrate 22, a second electrode 32 arranged on the metal layer 40, and a It includes an insulating film 35 , a semiconductor laminate 1 arranged on the second electrode 32 and the insulating film 35 , and a first electrode 31 arranged on the semiconductor laminate 1 .
Semiconductor laminate 1 includes, in order from the second electrode 32 side, p-side nitride semiconductor layer 13 electrically connected to second electrode 32 , active layer 12 , and n-side nitride semiconductor layer 11 . The first electrode 31 is arranged on the n-side nitride semiconductor layer 11 and electrically connected to the n-side nitride semiconductor layer 11 . The semiconductor laminate 1 is bonded to the second substrate 22 via the second electrode 32 , the insulating film 35 and the metal layer 40 . As a result, for example, by using a conductive semiconductor substrate or a metal substrate as the second substrate 22 , power can be supplied to the semiconductor stack 1 through the second substrate 22 . The semiconductor laminate 1 having such a structure can cause the active layer 12 to emit light by applying a voltage between the first electrode 31 and the second electrode 32 . Light emitted from the semiconductor stacked body 1 is mainly emitted from the surface of the n-side nitride semiconductor layer 11 on which the first electrode 31 is provided.
The light emitting device 10 of this embodiment will be described in detail below.

<n-side nitride semiconductor layer>
The n-side nitride semiconductor layer 11 has, for example, a nitride semiconductor layer doped with an n-type impurity such as Si. The n-side nitride semiconductor layer 11 is configured including a plurality of layers. Further, the n-side nitride semiconductor layer 11 may partially include, for example, an undoped semiconductor layer. Here, the undoped semiconductor layer refers to a layer grown without adding n-type impurities during growth. You can

<p-side nitride semiconductor layer>
The p-side nitride semiconductor layer 13 has, for example, a nitride semiconductor layer doped with a p-type impurity such as Mg. The p-side nitride semiconductor layer 13 is configured including a plurality of layers. Further, the p-side nitride semiconductor layer 13 may partially include, for example, an undoped semiconductor layer. The p-side nitride semiconductor layer 13 has, for example, a p-type clad layer provided in contact with the active layer 12 and a p-type contact layer provided on the p-type clad layer. The bandgap energy of the p-type cladding layer is, for example, greater than the bandgap energy of the second barrier layer 2 . The bandgap energy of the p-type contact layer is smaller than the bandgap energy of the second barrier layer 2, for example.

<Active layer>
The active layer 12 includes a plurality of well layers made of nitride semiconductors and a plurality of barrier layers made of nitride semiconductors. As shown in FIG. 2, the multiple quantum well structure according to the present embodiment includes, in order from the n-side nitride semiconductor layer 11 side, a barrier layer 4 including a first barrier layer 2 and a second barrier layer 3, and a well layer 5. and alternately.

(First barrier layer)
The first barrier layer 2 is laminated on the n-side nitride semiconductor layer 11 . The first barrier layer 2 is a nitride semiconductor layer containing Al and Ga. A nitride semiconductor layer containing Al and Ga is, for example, a ternary compound. The general formula of the first barrier layer 2 is, for example, Al _a Ga _1-a N (0<a<1). The Al mixed crystal ratio of the first barrier layer 2 is preferably 0.05≦a≦0.15.
The first barrier layer 2 has a bandgap energy greater than that of the second barrier layer 3, as shown in FIG. Also, the first barrier layer 2 has a bandgap energy greater than that of the well layer 5 .
The film thickness of the first barrier layer 2 is preferably formed thicker than the film thickness of the second barrier layer 3 . The film thickness of the first barrier layer 2 is, for example, 10 nm or more and 35 nm or less.

(Second barrier layer)
A second barrier layer 3 is laminated on the first barrier layer 2 . The second barrier layer 3 is a nitride semiconductor layer containing Al, Ga, and In. A nitride semiconductor layer containing Al, Ga, and In is, for example, a quaternary compound. The general formula of the second barrier layer 3 is, for example, Al _b In _c Ga _1-bc N (0<b<1, 0<c<1, b+c<1). The Al mixed crystal ratio of the second barrier layer 3 is preferably 0.05≦b≦0.15. In addition, the In mixed crystal ratio of the second barrier layer 3 is preferably 0.0001≦c≦0.01.
The second barrier layer 3 has a bandgap energy smaller than the bandgap energy of the first barrier layer 2 and larger than the bandgap energy of the well layer 5, as shown in FIG. In other words, the semiconductor laminate 1 of the light emitting device 10 according to this embodiment has a bandgap energy structure having a relationship of bandgap energy of the first barrier layer>bandgap energy of the second barrier layer>bandgap energy of the well layer. have. Thus, since the second barrier layer 3 has a bandgap energy smaller than that of the first barrier layer 2 , there is a concern that light absorption may occur more easily than the first barrier layer 2 . Therefore, the film thickness of the second barrier layer 3 is preferably formed thinner than the film thickness of the first barrier layer 2 . The film thickness of the second barrier layer 3 is, for example, 3 nm or more and 25 nm or less.

(well layer)
A well layer 5 is laminated on the second barrier layer 3 . The well layer 5 is a nitride semiconductor layer and emits ultraviolet light. As used herein, ultraviolet light means light with a wavelength of 400 nm or less. The nitride semiconductor layer is, for example, a ternary compound. The general formula of the well layer 5 is, for example, In _e Ga _1-e N (0≦e<1). The In mixed crystal ratio is preferably 0≦e≦0.09. The well layer 5 having such a composition emits ultraviolet light. The peak wavelength of light emitted from the well layer 5 is, for example, 365 nm or more and 400 nm or less. Examples of the peak wavelength of the well layer 5 are 365 nm and 385 nm.
In addition, it is desirable that the In mixed crystal ratio of the well layer 5 is the same as the In mixed crystal ratio of the second barrier layer 3 . By making the In mixed crystal ratio of the well layer 5 and the In mixed crystal ratio of the second barrier layer 3 the same, the lattice constant difference between the well layer 5 and the second barrier layer 3 can be reduced. and the second barrier layer 3, the lattice relaxation is suppressed.
The well layer 5 has a bandgap energy smaller than that of the first barrier layer 2, as shown in FIG. Also, the well layer 5 has a bandgap energy smaller than the bandgap energy of the second barrier layer 3 .
The film thickness of the well layer 5 is, for example, 5 nm or more and 30 nm or less. Of the plurality of well layers 5 , the film thickness of some well layers 5 may be different from the film thickness of the other well layers 5 .

By stacking the well layer 5 on the second barrier layer 3 containing Al, Ga, and In in this manner, lattice relaxation at the interface between the second barrier layer 3 and the well layer 5 can be suppressed. Moreover, the well layer 5 can be grown with good crystallinity on the second barrier layer 3 having a small surface roughness.
Thus, the active layer in this embodiment includes, in order from the n-side nitride semiconductor layer side, the first barrier layer 2, the second barrier layer 3 having a bandgap energy smaller than the bandgap energy of the first barrier layer 2, and a well layer 5 having a bandgap energy smaller than that of the second barrier layer 3 . Thereby, the crystallinity of the well layer 5 can be improved, and the electron confinement effect in the well layer 5 can be enhanced. As a result, the recombination probability of electrons and holes can be increased, and the light emission output of the light emitting device 10 can be increased.

In the active layer 12 in this embodiment, as shown in FIG. 3, all the barrier layers 4 are composed of two barrier layers, the first barrier layer 2 and the second barrier layer 3, but are limited to this. not a thing For example, among the plurality of barrier layers 4, some barrier layers 4 are composed of two barrier layers, the first barrier layer 2 and the second barrier layer 3, and the other barrier layers 4 are composed of the first barrier layer 2 and the second barrier layer 3. and the second barrier layer 3 may be composed of one of the barrier layers. For example, as shown in FIG. 4A, among the plurality of barrier layers 4, the barrier layer in contact with the p-side nitride semiconductor layer 13 may be composed of the first barrier layer 2 alone. Thereby, the recombination probability in well layer 5 can be further improved. Further, for example, as shown in FIG. 4B, among the plurality of barrier layers 4, the barrier layer 4 in contact with the well layer 5 closest to the p-side nitride semiconductor layer 13 is formed by the first barrier layer 2 and the second barrier layer 3. and the other barrier layer 4 may be composed only of the first barrier layer 2 . As a result, an electron confinement effect is obtained in the well layer 5 located near the p-side nitride semiconductor layer 13 and in which recombination of electrons and holes is likely to occur. and the second barrier layer 3, light absorption by the second barrier layer 2 can be suppressed.

2. Method for Manufacturing Light-Emitting Device The method for manufacturing the light-emitting device 10 according to this embodiment includes:
(1) an n-side nitride semiconductor layer growing step of growing an n-side nitride semiconductor layer;
(2) an active layer growth step of growing an active layer that emits ultraviolet light and includes a plurality of well layers made of nitride semiconductors and a plurality of barrier layers made of nitride semiconductors on the n-side nitride semiconductor layer;
(3) a p-side nitride semiconductor layer growing step of growing a p-side nitride semiconductor layer on the active layer;
(4) an electrode forming step of forming a first electrode and a second electrode;
(5) a cutting step;
including.
Furthermore, the active layer growth step is
(2-1) a first barrier layer growth step of growing a first barrier layer using a source gas containing an Al source gas, a Ga source gas, and an N source gas;
(2-2) a second barrier layer growth step of growing a second barrier layer on the first barrier layer by using a source gas containing an Al source gas, a Ga source gas, an In source gas, and an N source gas;
(2-3) a well layer growing step of growing a well layer having a bandgap energy smaller than that of the second barrier layer on the second barrier layer using a raw material gas containing a Ga raw material gas and an N raw material gas;
including.

A method for manufacturing the light emitting device of this embodiment will be described in detail below with reference to FIGS. 5 to 14, the sizes of the members may be exaggerated in order to facilitate understanding of the drawings. In particular, in FIGS. 6 to 8, the thicknesses of the barrier layers and well layers are exaggerated.

(1) n-Side Nitride Semiconductor Layer Growth Step In the n-side nitride semiconductor layer growth step, as shown in FIG. By growing the n-type contact layer and the n-type clad layer, the n-side nitride semiconductor layer 11 including the n-type contact layer and the n-type clad layer is formed from the first substrate 21 side. The n-side nitride semiconductor layer 11 may be formed on the first substrate 21 with a buffer layer interposed therebetween.

(2) Active Layer Growth Step Next, the active layer 12 is formed on the n-side nitride semiconductor layer 11 . The active layer 12 includes a plurality of well layers made of nitride semiconductors and a plurality of barrier layers made of nitride semiconductors. The active layer 12 is formed by the following steps.

(2-1) First Barrier Layer Growth Step First, as shown in FIG. A first barrier layer 2 is grown. When the composition of the first barrier layer 2 is, for example, AlGaN, the flow rate of the Al raw material gas is set to 0.5 sccm or more and 2 sccm or less, the flow rate of the Ga raw material gas is set to 20 sccm or more and 50 sccm or less, and the N raw material gas is set to The first barrier layer 2 can be formed by setting the flow rate of between 4 slm and 10 slm.
The first barrier layer 2 is desirably grown to a thickness of 10 nm or more and 35 nm or less.

(2-2) Second Barrier Layer Growth Step Next, as shown in FIG. A second barrier layer 3 is grown on the . When the composition of the second barrier layer 3 is AlInGaN, for example, the flow rate of the Al raw material gas is set to 0.5 sccm or more and 2 sccm or less, and the flow rate of the In raw material gas is set to 3 sccm or more and 15 sccm or less, preferably 5 sccm or more and 10 sccm. The second barrier layer 3 can be formed by setting the following, setting the flow rate of the Ga source gas to 20 sccm or more and 50 sccm or less, and setting the flow rate of the N source gas to 4 slm or more and 10 slm or less. Thus, the flow rates of the Al source gas, the Ga source gas, and the N source gas in the second barrier layer growth step are the same as those of the Al source gas, the Ga source gas, and the N source gas in the first barrier layer growth step. can be set to be the same as As a result, In is added to these three source gases without stopping the release of the Al source gas, the Ga source gas, and the N source gas in the first barrier layer growth step, or without changing the flow rates of these source gases. The second barrier layer 3 can be formed by mixing the raw material gases at a predetermined flow rate. That is, the first barrier layer 2 and the second barrier layer 3 can be formed by continuous steps.
It is desirable to grow the second barrier layer 3 so that its thickness is thinner than that of the first barrier layer 2 . It is desirable to grow the second barrier layer 3 to a film thickness of 3 nm or more and 25 nm or less.

(2-3) Well Layer Growth Step Next, as shown in FIG. 8, the well layer 5 is grown on the second barrier layer 3 using a source gas containing Ga source gas and N source gas. For example, when the composition of the well layer 5 is InGaN, the flow rate of the In source gas is set to 6 sccm or more and 25 sccm or less, the flow rate of the Ga source gas is set to 20 sccm or more and 50 sccm or less, and the flow rate of the N source gas is set to 4 slm. By setting the thickness to 10 slm or less, the well layer 5 can be formed. In the well layer growing step, it is preferable to grow the well layer 5 without introducing the Al raw material gas. In other words, it is preferable to grow the well layer 5 by setting the flow rate of the Al source gas to 0 sccm.
The well layer 5 is desirably grown to a film thickness of 5 nm or more and 30 nm or less.

An active layer including a plurality of first barrier layers 2, a plurality of second barrier layers 3, and a plurality of well layers 5 is formed by repeating the first barrier layer growth step, the second barrier layer growth step, and the well layer growth step. 12 are formed. For example, the active layer growth process ends with the second barrier layer growth process. In FIG. 8, one first barrier layer 2, one second barrier layer 3, and one well layer 5 are collectively labeled as the active layer 12 for easy understanding of the drawing. there is

(3) p-side nitride semiconductor layer growth step Then, on the active layer 12, for example, a p-type clad layer and a p-type contact layer are grown to form a p-type clad layer and a p-type layer in order from the active layer 12 side. A p-side nitride semiconductor layer 13 including a contact layer is formed.
Through these steps, as shown in FIG. 9, a semiconductor laminate structure 1a having an n-side nitride semiconductor layer 11, an active layer 12, and a p-side nitride semiconductor layer 13 is formed on a first substrate 21. A first wafer 100 is prepared.

(4) Electrode forming step of forming first electrode and second electrode Next, as shown in FIG. A patterned second electrode 32 is formed. Then, as shown in FIG. 11, an insulating film 35 is formed on a portion of the p-side nitride semiconductor layer 13 where the second electrode 32 is not formed. A metal layer 40a is formed. For the insulating film 35, for example, after forming a resist on the second electrode 32, an insulating film is formed on a portion of the p-side nitride semiconductor layer 13 where the second electrode 32 is not formed and on the resist, It can be formed by removing the resist together with the insulating film formed over the resist.

Next, as shown in FIG. 12, a second substrate 22 having a metal layer 40b formed on one surface is separately prepared, and the metal layer 40b of the second substrate 22 and the metal layer 40a of the first substrate 21 are separated. Join. Thereby, the second substrate 22 is bonded onto the p-side nitride semiconductor layer 13 via the second electrode 32, the insulating film 35, and the metal layers 40a and 40b. After bonding the second substrate 22, the first substrate 21 is removed by, for example, laser lift-off or wet etching.

As described above, the semiconductor laminate structure 1a formed on the first substrate 21 is transferred onto the second substrate 22 with the metal layer 40, the second electrode 32 and the insulating film 35 interposed therebetween. The metal layer 40 is a layer formed by bonding the metal layer 40a and the metal layer 40b. In this way, a second wafer 200 having a semiconductor multilayer structure 1a with the n-side nitride semiconductor layer 11 exposed on the surface on the second substrate 22 as shown in FIG. 13 is prepared. That is, in the second wafer 200, the p-side nitride semiconductor layer 13, the active layer 12, and the n-side nitride semiconductor layer are formed on the second substrate 22 with the metal layer 40, the second electrode 32, and the insulating film 35 interposed therebetween. 11 are stacked in order from the second substrate 22 side.

Next, as shown in FIG. 14, a portion of the semiconductor laminate structure 1a of the second wafer 200 is removed by dry etching such as reactive ion etching, thereby separating into a plurality of semiconductor laminates 1. . A first electrode 31 having a predetermined pattern is formed on the n-side nitride semiconductor layer 11 of the second wafer 200 . The first electrode 31 can be formed by a lift-off process using a resist or an etching process, similarly to the method of forming the second electrode 32 described above.

(5) Cutting Step Finally, the second wafer 200 on which the first electrodes 31 are formed is divided into individual light emitting elements 10 of desired size. This division is performed along predetermined cutting positions CL shown in FIG. 14 by dicing or the like.

Example 1.
A light-emitting device of Example 1 was fabricated as follows.

First, a first substrate 21 made of sapphire is prepared, and an n-type contact layer and an n-type cladding layer are grown thereon to form an n-type contact layer and an n-type cladding layer in order from the first substrate 21 side. A side nitride semiconductor layer 11 was formed.

Next, a first barrier layer 2 made of Al _0.095 Ga _0.905 N was laminated on the n-side nitride semiconductor layer 11 . The film thickness of the first barrier layer 2 was grown to a thickness of 29 nm. The flow rate of each source gas when growing the first barrier layer 2 was set to 1.78 sccm for the Al source gas, 43 sccm for the Ga source gas, and 7 slm for the N source gas.

Next, a well layer 5 made of In _0.005 Ga _0.995 N was laminated on the first barrier layer 2 . The thickness of the well layer 5 was grown to 8 nm. The flow rate of each raw material gas when growing the well layer 5 was set to 15 sccm for the In raw material gas, 38 sccm for the Ga raw material gas, and 7 slm for the N raw material gas.

The lamination structure of the first barrier layer 2 and the well layer 5 was repeated four times.

Next, a first barrier layer 2 made of Al _0.095 Ga _0.905 N was laminated on the well layer 5 . The film thickness of the first barrier layer 2 was grown to a thickness of 15 nm. The flow rate of each source gas when growing the first barrier layer 2 was set to 1.78 sccm for the Al source gas, 43 sccm for the Ga source gas, and 7 slm for the N source gas.

Next, a second barrier layer 3 made of Al _0.0945 In _0.0005 Ga _0.9050 N was laminated on the first barrier layer 2 . The second barrier layer 3 was grown to a thickness of 14 nm. The flow rate of each source gas when growing the second barrier layer 3 was set to 1.78 sccm for the Al source gas, 6 sccm for the In source gas, 43 sccm for the Ga source gas, and 43 sccm for the N source gas. 7 slm. The second barrier layer 3 was grown by mixing the Al raw material gas, the Ga raw material gas, and the N raw material gas used when growing the first barrier layer 2 with the In raw material gas set to the above flow rate.

Next, a well layer 5 made of In _0.005 Ga _0.995 N was laminated on the second barrier layer 3 . The thickness of the well layer 5 was grown to 15 nm. The flow rate of each raw material gas when growing the well layer 5 was set to 15 sccm for the In raw material gas, 38 sccm for the Ga raw material gas, and 7 slm for the N raw material gas.

After that, an active layer 12 was formed by laminating a barrier layer made of AlGaN on the well layer 5 formed last.

After forming the active layer 12 grown in this manner, the p-side nitride semiconductor layer 13 including the p-type clad layer and the p-type contact layer was formed to prepare the first wafer 100 .

Next, a second electrode 32 having a predetermined pattern is formed on the p-side nitride semiconductor layer 13 of the first wafer 100 and transferred to the second substrate 22 via the metal layer 40 . After that, the first substrate 21 was removed, the first electrode 31 having a predetermined pattern was formed on the n-side nitride semiconductor layer 11 , and the light emitting elements 10 were cut.

The light emitting device of Example 1 formed as described above was evaluated for light emission output when a current of 1000 mA was applied. Further, the output was measured when driven at temperatures of 25° C. and 85° C., respectively, and the output retention rate (output at temperature of 85° C./output at temperature of 25° C.) was evaluated. Furthermore, the half width of the emission wavelength of the light emitting element and the reverse voltage were evaluated.
As a result, the light emitting output of the light emitting device of Example 1 was 1806.7 mW. Further, the output retention rate was 85.3%, the half width of the emission wavelength was 8.6 nm, and the reverse voltage was 9.0V.

Reference example 1.
A light-emitting device of Reference Example 1 was fabricated in the same manner as the light-emitting device of Example 1, except that the barrier layer in the light-emitting device of Example 1 was a single layer composed of AlGaN. As for the flow rate of each source gas when growing the barrier layer, the Al source gas was set to 1.78 sccm, the Ga source gas was set to 43 sccm, and the N source gas was set to 7 slm. The film thickness of the barrier layer was grown to 29 nm.
The light emitting device of Reference Example 1 formed as described above was evaluated for light emission output when a current of 1000 mA was passed. Further, in the same manner as in Example 1, the output retention rate, the half width of the emission wavelength, and the reverse voltage were evaluated.
As a result, the light emitting output of the light emitting element of Reference Example 1 was 1779.6 mW. Further, the output retention rate was 84.7%, the half width of the emission wavelength was 8.7 nm, and the reverse voltage was 8.5V.

Table 1 shows the evaluation results of Example 1 and Reference Example 1. In addition, in Table 1, when the barrier layer is composed of the first barrier layer and the second barrier layer, it is described as "first barrier layer/second barrier layer". The description of "first barrier layer/second barrier layer" means that the first barrier layer and the second barrier layer are laminated in order from the n-side nitride semiconductor layer side.

From these results, the light emitting device of Example 1 in which the barrier layer 4 having the first barrier layer 2 and the second barrier layer 3 having a bandgap energy smaller than the bandgap energy of the first barrier layer 2 was formed, It was confirmed that the light emission output was higher than that of the light emitting device of Reference Example 1. Further, it was confirmed that the light-emitting device of Example 1 was superior to the light-emitting device of Reference Example 1 in terms of the output maintenance rate, the half width of the emission wavelength, and the reverse voltage. From this, it is assumed that the light-emitting device of Example 1 has better surface roughness in the well layer than the light-emitting device of Reference Example 1, and lattice relaxation between the barrier layer and the well layer is suppressed. be done.

Example 2.
A light-emitting device of Example 2 was fabricated as follows.

First, a substrate made of sapphire is prepared, and an n-type contact layer and an n-type cladding layer are grown thereon, thereby forming an n-side nitride including an n-type contact layer and an n-type cladding layer in order from the first substrate 21 side. A semiconductor layer 11 was formed.

Next, a first barrier layer 2 made of Al _0.095 Ga _0.905 N was laminated on the n-side nitride semiconductor layer 11 . The film thickness of the first barrier layer 2 was grown to a thickness of 15 nm. The flow rate of each source gas when growing the first barrier layer 2 was set to 1.53 sccm for the Al source gas, 39 sccm for the Ga source gas, and 7 slm for the N source gas.

Next, a second barrier layer 3 made of Al _0.0945 In _0.0005 Ga _0.9050 N was laminated on the first barrier layer 2 . The second barrier layer 3 was grown to a thickness of 14 nm. The flow rate of each source gas when growing the second barrier layer 3 was set to 1.53 sccm for the Al source gas, 6 sccm for the In source gas, 39 sccm for the Ga source gas, and 39 sccm for the N source gas. 7 slm. The second barrier layer 3 was grown by mixing the Al raw material gas, the Ga raw material gas, and the N raw material gas used when growing the first barrier layer 2 with the In raw material gas set to the above flow rate.

Next, a well layer 5 made of In _0.005 Ga _0.995 N was laminated on the second barrier layer 3 . The thickness of the well layer 5 was grown to 8 nm. The flow rate of each raw material gas when growing the well layer 5 was set to 15 sccm for the In raw material gas, 45 sccm for the Ga raw material gas, and 7 slm for the N raw material gas.

The lamination structure of the first barrier layer 2, the second barrier layer 3, and the well layer 5 was repeated four times.

Next, a first barrier layer 2 made of Al _0.095 Ga _0.905 N was laminated on the well layer 5 . The film thickness of the first barrier layer 2 was grown to a thickness of 15 nm. The flow rate of each source gas when growing the first barrier layer 2 was set to 1.53 sccm for the Al source gas, 39 sccm for the Ga source gas, and 7 slm for the N source gas.

Next, a second barrier layer 3 made of Al _0.0945 In _0.0005 Ga _0.9050 N was laminated on the first barrier layer 2 . The second barrier layer 3 was grown to a thickness of 14 nm. The flow rate of each source gas when growing the second barrier layer 3 was set to 1.53 sccm for the Al source gas, 6 sccm for the In source gas, 39 sccm for the Ga source gas, and 39 sccm for the N source gas. 7 slm. The second barrier layer 3 was grown by mixing the Al raw material gas, the Ga raw material gas, and the N raw material gas used when growing the first barrier layer 2 with the In raw material gas set to the above flow rate.

Next, a well layer 5 made of In _0.005 Ga _0.995 N was laminated on the second barrier layer 3 . The thickness of the well layer 5 was grown to 15 nm. The flow rate of each raw material gas when growing the well layer 5 was set to 15 sccm for the In raw material gas, 45 sccm for the Ga raw material gas, and 7 slm for the N raw material gas.

After that, an active layer 12 was formed by laminating a barrier layer made of AlGaN on the well layer 5 formed last.

After forming the active layer 12 grown in this manner, the p-side nitride semiconductor layer 13 including the p-type clad layer and the p-type contact layer was formed to prepare the first wafer 100 .

Next, a second electrode 32 having a predetermined pattern is formed on the p-side nitride semiconductor layer 13 of the first wafer 100 , and a first electrode 31 having a predetermined pattern is formed on the n-side nitride semiconductor layer 11 . , and cut every 10 light emitting elements.

The light emitting device of Example 2 formed as described above was evaluated for light emission output when a current of 100 mA was applied. In addition, the half width of the emission wavelength of the light emitting device and the surface roughness of the well layer were evaluated.
As a result, the light output of the light emitting device of Example 2 was 48.7 mW. In addition, the half width of the emission wavelength was 12.4 nm, and the surface roughness was 5.3 nm.

Reference example 2.
The light-emitting device of Reference Example 2 was manufactured in the same manner as the light-emitting device of Example 2, except that the barrier layer was a single layer composed of Al _0.095 Ga _0.905 N. made. As for the flow rate of each source gas when growing the barrier layer, the Al source gas was set to 1.53 sccm, the Ga source gas was set to 39 sccm, and the N source gas was set to 7 slm. The film thickness of the barrier layer was grown to 29 nm.
The light emitting device of Reference Example 2 formed as described above was evaluated for light emission output when a current of 100 mA was passed. Further, in the same manner as in Example 2, the half width of the emission wavelength of the light emitting element and the surface roughness of the well layer were evaluated.
As a result, the light emitting output of the light emitting element of Reference Example 2 was 47.4 mW. Further, the half width of the emission wavelength was 12.6 nm, and the surface roughness was 6.0 nm.

Reference example 3.
Reference Example 3 was performed in the same manner as the light emitting device of Example 2, except that in the light emitting device of Example 2, a single layer composed of Al _0.0945 In _0.0005 Ga _0.9050 N was used as the barrier layer. was fabricated. As for the flow rate of each source gas when growing the barrier layer, the Al source gas was set to 1.53 sccm, the In source gas was set to 6 sccm, the Ga source gas was set to 39 sccm, and the N source gas was set to 7 slm. did. The film thickness of the barrier layer was grown to 29 nm.
The light emitting device of Reference Example 3 formed as described above was evaluated for light emission output when a current of 100 mA was applied. Also, in the same manner as in Example 2, the half width of the light emitting device and the surface roughness of the well layer were evaluated.
As a result, the light emitting output of the light emitting element of Reference Example 3 was 48 mW. Further, the half width of the emission wavelength was 12.3 nm, and the surface roughness was 4.7 nm.

Reference example 4.
Example 2 except that the first barrier layer was Al _0.0945 In _0.0005 Ga _0.9050 N and the second barrier layer was Al _0.095 Ga _0.905 N in the light emitting device of Example 1. A light-emitting device of Reference Example 4 was fabricated in the same manner as the light-emitting device of No. That is, in the light emitting device of Reference Example 4, the composition of the first barrier layer was the same as that of the second barrier layer of Example 2, and the composition of the second barrier layer was the same as that of the first barrier layer of Example 2. It is a light-emitting device manufactured by In such a light-emitting device of Reference Example 4, the bandgap energy of the second barrier layer is higher than the bandgap energy of the first barrier layer. Therefore, the bandgap energy structure of the semiconductor laminate in the light emitting device of Reference Example 4 has a relationship of bandgap energy of the second barrier layer>bandgap energy of the first barrier layer>bandgap energy of the well layer. .
The flow rate of each source gas when growing the first barrier layer was set to 1.53 sccm for the Al source gas, 6 sccm for the In source gas, 39 sccm for the Ga source gas, and 7 slm for the N source gas. set to The thickness of the first barrier layer was grown to 15 nm. As for the flow rate of each source gas when growing the second barrier layer, the Al source gas was set to 1.53 sccm, the Ga source gas was set to 39 sccm, and the N source gas was set to 7 slm. The thickness of the second barrier layer was grown to 14 nm.
The light emitting device of Reference Example 4 formed as described above was evaluated for light emission output when a current of 100 mA was passed. Further, in the same manner as in Example 2, the half width of the emission wavelength of the light emitting element and the surface roughness of the well layer were evaluated.
As a result, the light emitting output of the light emitting element of Reference Example 4 was 47.3 mW. Further, the half width of the emission wavelength was 12.5 nm, and the surface roughness was 6.6 nm.

The evaluation results of Example 2 and Reference Examples 2 to 4 are shown in Table 2. In Table 2, when the barrier layer is composed of the first barrier layer and the second barrier layer, it is described as "first barrier layer/second barrier layer". The description of "first barrier layer/second barrier layer" means that the first barrier layer and the second barrier layer are laminated in order from the n-side nitride semiconductor layer side.

From these results, the light-emitting device of Example 2 in which the barrier layer 4 having the first barrier layer 2 and the second barrier layer 3 having a bandgap energy smaller than the bandgap energy of the first barrier layer 2 was formed, It was confirmed that the luminescence output was higher than that of the light emitting devices of Reference Examples 2 to 4.
Further, from Example 2 and Reference Example 4, the light-emitting element of Example 2, in which the bandgap energy relationship is the first barrier layer>the second barrier layer, has the bandgap energy relationship of the second barrier layer>the first barrier layer. It was confirmed that the light emitting output was higher than that of the light emitting device of Reference Example 4, which was a layer. This is presumably because Example 2 has a higher electron confinement effect than Reference Example 4. In addition, the light emitting device of Example 2 has the same emission wavelength half width as the light emitting devices of Reference Examples 2 to 4, and the surface roughness of the well layer is a better value than those of Reference Examples 2 and 4. It was confirmed that From this, it is presumed that the light-emitting device of Example 2 has better crystallinity in the barrier layer and the well layer than the light-emitting devices of Reference Examples 2 and 4. The surface roughness of the light-emitting device of Example 2 was inferior to that of Reference Example 3 in which the composition of the barrier layer was AlInGaN alone. It was confirmed to be higher than the light emitting device of Reference Example 3. From this, it is presumed that the light-emitting device of Example 2 has a high electron confinement effect while improving the crystallinity of the barrier layer and the well layer.

Although embodiments and examples of the present invention have been described above, the disclosed contents may vary in details of construction, and combinations of elements, changes in order, etc. in the embodiments and examples are within the scope of the claimed invention. And it can be realized without deviating from the idea.

1 semiconductor laminate 1a semiconductor laminate structure 2 first barrier layer 3 second barrier layer 4 barrier layer 5 well layer 10 semiconductor element 11 n-side nitride semiconductor layer 12 active layer 13 p-side nitride semiconductor layer 21 first substrate 22 Second substrate 31 First electrode 32 Second electrode 35 Insulating films 40, 40a, 40b Metal layer 100 First wafer 200 Second wafer

Claims (17)

an n-side nitride semiconductor layer;
an active layer emitting ultraviolet light, comprising a plurality of well layers made of a nitride semiconductor provided on the n-side nitride semiconductor layer, and a plurality of barrier layers made of a nitride semiconductor;
a p-side nitride semiconductor layer provided on the active layer;
At least one of the plurality of barrier layers includes, in order from the n-side nitride semiconductor layer side, a first barrier layer containing Al and Ga, and provided in contact with the first barrier layer, Al, a second barrier layer containing Ga and In and having a lower bandgap energy than the first barrier layer;
At least one well layer among the plurality of well layers is provided in contact with the second barrier layer, has a bandgap energy smaller than that of the second barrier layer, and has a thickness thinner than that of the second barrier layer. A light-emitting element having A barrier layer positioned closest to the p-side nitride semiconductor layer among the plurality of barrier layers is composed of the first barrier layer, and the first barrier layer is provided in contact with the p-side nitride semiconductor layer. The light emitting device according to claim 1. 2. The first barrier layer and the second barrier layer, of the plurality of barrier layers, only a barrier layer located on a well layer located closest to the p-side nitride semiconductor layer includes the first barrier layer and the second barrier layer. 3. The light-emitting device according to 2. at least one of the plurality of well layers contains In;
4. The light emitting device according to claim 1, wherein at least one of the plurality of well layers has the same In composition ratio as the second barrier layer. The light emitting device according to any one of claims 1 to 4, wherein the film thickness of the second barrier layer is thinner than the film thickness of the first barrier layer. The light-emitting device according to any one of claims 1 to 5 , wherein each of the plurality of barrier layers has the first barrier layer and the second barrier layer. an n-side nitride semiconductor layer growing step of growing an n-side nitride semiconductor layer; and a plurality of well layers made of a nitride semiconductor and a plurality of barrier layers made of a nitride semiconductor on the n-side nitride semiconductor layer. and a p-side nitride semiconductor layer growing step of growing a p-side nitride semiconductor layer on the active layer. There is
The active layer growing step includes:
a first barrier layer growing step of growing a first barrier layer using a source gas containing an Al source gas, a Ga source gas, and an N source gas;
a second barrier layer growing step of growing a second barrier layer on the first barrier layer by using a source gas containing an Al source gas, a Ga source gas, an In source gas, and an N source gas;
The well layer having a bandgap energy smaller than that of the second barrier layer is grown on the second barrier layer using a raw material gas containing a Ga raw material gas and an N raw material gas to a thickness thinner than that of the second barrier layer. a layer growth step;
A method of manufacturing a light emitting device comprising: growing a barrier layer positioned closest to the p-side nitride semiconductor layer among the plurality of barrier layers and in contact with the p-side nitride semiconductor layer by a first barrier layer growing step;
8. The method according to claim 7, wherein, among the plurality of barrier layers, a barrier layer other than the barrier layer in contact with the p-side nitride semiconductor layer is grown by the first barrier layer growing step and the second barrier layer growing step. A method for manufacturing a light-emitting device. Of the plurality of barrier layers, only the barrier layer located on the well layer located closest to the p-side nitride semiconductor layer is grown by the first barrier layer growing step and the second barrier layer growing step. 9. The method for manufacturing a light-emitting device according to claim 7 or 8, wherein The flow rates of the Al source gas, the Ga source gas, and the N source gas in the second barrier layer growth step are the same as the Al source gas, the Ga source gas, and the N source gas in the first barrier layer growth step. 10. The method for manufacturing a light-emitting device according to claim 7, wherein each flow rate of the gas is the same. In the first barrier layer growing step,
setting the flow rate of the Al source gas to 0.5 sccm or more and 2 sccm or less, setting the flow rate of the Ga source gas to 20 sccm or more and 50 sccm or less, and setting the flow rate of the N source gas to 4 slm or more and 10 slm or less;
In the second barrier layer growing step,
The flow rate of the Al source gas is set to 0.5 sccm or more and 2 sccm or less, the flow rate of the Ga source gas is set to 20 sccm or more and 50 sccm or less, the flow rate of the N source gas is set to 4 slm or more and 10 slm or less, and the In source gas is set to 11. The method for manufacturing a light-emitting device according to claim 7, wherein the gas flow rate is set to 3 sccm or more and 15 sccm or less . 12. The method of manufacturing a light emitting device according to claim 11 , wherein in said second barrier layer growing step, the flow rate of said In source gas is set to 5 sccm or more and 10 sccm or less. In the well layer growing step,
The flow rate of the Ga source gas is set to 20 sccm or more and 50 sccm or less, the flow rate of the N source gas is set to 4 slm or more and 10 slm or less, and the flow rate of the In source gas is set to 6 sccm or more and 25 sccm or less . A method for manufacturing the described light-emitting device. 14. The method of manufacturing a light emitting device according to claim 13 , wherein in the well layer growing step, the well layer is grown without introducing the Al source gas. 15. The method of manufacturing a light-emitting device according to claim 7 , wherein in said second barrier layer growing step, said second barrier layer is grown to be thinner than said first barrier layer. 16. The method of manufacturing a light-emitting device according to claim 7 , wherein the first barrier layer is grown to a thickness of 10 nm or more and 35 nm or less in the step of growing the first barrier layer. 17. The method of manufacturing a light-emitting device according to claim 7 , wherein the second barrier layer is grown to a thickness of 3 nm or more and 25 nm or less in the step of growing the second barrier layer.

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