JP2023141196A - Method of manufacturing light-emitting element and light-emitting element - Google Patents

Abstract

To provide a method of manufacturing a light-emitting element, and the light-emitting element, capable of achieving a high luminous efficiency and a low threshold voltage.SOLUTION: A light emitting element includes, on an Al-containing nitride semiconductor substrate, a semiconductor lamination part in which a first conductivity-type cladding layer including a nitride semiconductor layer of a first conductivity type, a light-emitting layer formed of a nitride semiconductor including one or more quantum wells, and a second conductivity-type cladding layer including a nitride semiconductor layer of a second conductivity type are laminated in this order. The light emitting element also includes, between the nitride semiconductor substrate and the first conductivity-type cladding layer, an altered nitride semiconductor layer in which a stoichiometric ratio between group III atoms and group V atoms is not 1:1, and 1×1018 cm-3 or more and 5×1019 cm-3 or less of hydrogen is contained. Such an altered nitride semiconductor layer is formed by subjecting a nitride buffer layer formed on the Al-containing nitride semiconductor substrate to heat treatment alternately in hydrogen and NH3 in an environment with a reactor pressure of 10 mbar or more and 50 mbar or less and a temperature of 1,200°C or above and 1,400°C or below.SELECTED DRAWING: Figure 1

Description

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

Since nitride semiconductors have a direct transition recombination mode, they can obtain high recombination efficiency and high optical gain, and are therefore suitable as materials for light-emitting diodes (LEDs) and laser diodes (LDs). Are suitable. Examples of laser diodes or light emitting diodes using nitride semiconductors include current injection laser diodes that emit laser light in the ultraviolet region (e.g., Non-Patent Document 1), and light emitting diodes that emit ultraviolet light (e.g. Non-patent document 2) is disclosed.

Zhang et at. , Applied Physics Express 12, 124003 (2019) J. R. Grandusky. , Applied Physics Express 6, 032101 (2013)

Although the laser diode described above is driven by pulses, continuous oscillation is required for practical applications. This continuous oscillation requires a reduction in the oscillation threshold current, that is, an increase in the efficiency of the light emitting layer and a reduction in the threshold voltage. In addition, the above-mentioned light emitting diode is required to have higher emission intensity, that is, higher efficiency of the light emitting layer and lower threshold voltage, from the viewpoint of enabling sterilization in a short time.
An object of the present disclosure is to provide a method for manufacturing a light emitting element and a light emitting element that achieve high efficiency of a light emitting layer and a reduction in threshold voltage.

In order to solve the above-mentioned problems, a method for manufacturing a light emitting element according to one embodiment of the present disclosure includes forming a nitride buffer layer containing Al on a nitride semiconductor substrate containing Al, and forming the nitride buffer layer in a reactor. Heat treatment is performed alternately in hydrogen and _NH3 in an environment where the pressure is 10 mbar or more and 50 mbar or less and 1200 °C or more and 1400 °C or less, and the stoichiometric ratio of group III atoms and group V atoms is not 1:1. a first conductivity type cladding including a first conductivity type nitride semiconductor layer is formed on the modified nitride semiconductor layer; and one or more conductivity type cladding layers are formed on the first conductivity type cladding layer. A light emitting layer made of a nitride semiconductor including a quantum well is formed, and a second conductivity type cladding layer including a second conductivity type nitride semiconductor layer is formed on the light emitting layer to form a semiconductor stacked section. .

Furthermore, in order to solve the above-mentioned problems, a light-emitting element according to one embodiment of the present disclosure includes a nitride semiconductor substrate containing Al, a semiconductor stacked portion disposed on the nitride semiconductor substrate, and a semiconductor stacked portion that includes: a first conductivity type cladding layer disposed on a substrate and including the substrate and a first conductivity type nitride semiconductor layer; and a nitride semiconductor disposed on the first conductivity type cladding layer and including one or more quantum wells. and a second conductivity type cladding layer disposed on the luminescence layer and including a second conductivity type nitride semiconductor layer, between the substrate and the first conductivity type cladding layer. is characterized by comprising a modified nitride semiconductor layer in which the stoichiometric ratio of group III atoms to group V atoms is not 1:1.

Further, a light emitting element according to another aspect of the present disclosure includes a nitride semiconductor substrate containing Al and a semiconductor stacked section disposed on the nitride semiconductor substrate, and the semiconductor stacked section is arranged on the nitride semiconductor substrate. a first conductivity type cladding layer disposed on the substrate and including a first conductivity type nitride semiconductor layer; and a light emitting device formed of a nitride semiconductor disposed on the first conductivity type cladding layer and including one or more quantum wells. and a second conductivity type cladding layer disposed on the light emitting layer and including a second conductivity type nitride semiconductor layer, and between the nitride semiconductor substrate and the first conductivity type cladding layer, The modified nitride semiconductor layer includes hydrogen in an amount of 1×10 ¹⁸ cm ⁻³ or more and 5×10 ¹⁹ cm ⁻³ or less.
Note that the above-mentioned summary of the invention does not list all the features of the present disclosure.

According to the present disclosure, it is possible to provide a method for manufacturing a light-emitting element and a light-emitting element that achieve high efficiency of a light-emitting layer and a reduction in threshold voltage.

FIG. 1 is a schematic cross-sectional view showing a configuration example of a light emitting element according to a first embodiment of the present disclosure. FIG. 2 is a schematic cross-sectional view showing a configuration example of a light emitting element according to a second embodiment of the present disclosure.

Hereinafter, a light emitting device according to the present disclosure will be described through embodiments, but the following embodiments do not limit the invention according to the claims. Furthermore, not all combinations of features described in the embodiments are essential to the solution of the invention.
Furthermore, in the following description, "above" and "below" do not necessarily mean a direction perpendicular to the ground. That is, the "up" and "down" directions are not limited to the direction of gravity. The terms "upper" and "lower" are merely convenient expressions for specifying the relative positional relationship among surfaces, films, substrates, etc., and do not limit the technical idea of the present invention. For example, if the page is rotated 180 degrees, "top" becomes "bottom" and "bottom" becomes "top".

1. Embodiment A light emitting element according to an embodiment of the present disclosure will be described.
(1.1) Structure of light emitting device The light emitting device according to the present embodiment includes a nitride semiconductor substrate containing Al and a semiconductor laminated portion disposed on the nitride semiconductor substrate, and the semiconductor laminated portion has a nitride semiconductor substrate. a first conductivity type cladding layer disposed on a semiconductor substrate and including a first conductivity type nitride semiconductor layer; and a nitride semiconductor disposed on the first conductivity type cladding layer and including one or more quantum wells. a second conductive type cladding layer disposed on the light emitting layer and including a second conductive type nitride semiconductor layer, and between the substrate and the first conductive type cladding layer. , comprising a modified nitride semiconductor layer. The altered nitride semiconductor layer is a layer in which the stoichiometric ratio of group III atoms and group V atoms is not 1:1, or contains hydrogen in an amount of 1×10 ¹⁸ cm ⁻³ or more and 5×10 ¹⁹ cm ^{−3 or} less .
Each layer of the light emitting device will be described in detail below.

<Nitride semiconductor substrate>
A nitride semiconductor substrate (hereinafter sometimes referred to as a substrate) includes a nitride semiconductor containing Al. The nitride semiconductor containing Al is, for example, AlN. That is, the substrate is preferably an AlN single crystal substrate. Further, the nitride semiconductor containing Al is not limited to AlN, and may be, for example, AlGaN. For example, when the substrate is a nitride semiconductor single crystal substrate such as AlN or AlGaN, the difference in lattice constant from the nitride semiconductor layer formed on the upper side of the substrate becomes small, allowing the nitride semiconductor layer to grow in a lattice-matched system. This can reduce threading dislocations.
The threading dislocation density of the substrate is preferably 5×10 ⁴ cm ⁻² or less. In particular, from the viewpoint of improving the emission intensity and reducing the oscillation threshold current, it is more preferable that the threading dislocation density is 1×10 ³ or more and 1×10 ⁴ cm ⁻² or less.

Here, "contains" in the expression "contains a nitride semiconductor" means that the layer mainly contains a nitride semiconductor, but this expression also includes cases where other elements are included. Specifically, the composition of this layer is changed by adding a small amount of an element other than the nitride semiconductor (for example, Ga (if Ga is not the main element), In, As, P, or Sb, etc., in a few percent or less). This expression also includes cases where minor changes are made. In expressing the composition of other layers, the word "contains" has the same meaning. Moreover, the small amount of elements contained is not limited to the above.

The substrate may also be doped n-type or p-type with donor or acceptor impurities. Further, the substrate may be a mixed crystal of a nitride semiconductor such as AlN and sapphire (Al ₂ O ₃ ), Si, SiC, MgO, Ga ₂ O ₃ , ZnO, GaN, or InN.
As an example, the substrate preferably has a layer thickness of 100 μm or more and 600 μm or less. Further, the plane orientation may be c-plane (0001), a-plane (11-20), m-plane (10-10), etc., but a c-plane (0001) substrate is more preferable. Furthermore, it can be formed on a surface inclined at some angle (for example, -4° to 4°, preferably -0.4° to 0.4°) from the normal direction of the c-plane (0001); Not limited to.

<Homoepitaxial layer>
The homoepitaxial layer is formed between the substrate and the modified nitride semiconductor layer, and is preferably formed over the entire surface of the substrate. By providing the homoepitaxial layer, a nitride semiconductor layer with a small difference in lattice constant and a small difference in thermal expansion coefficient and few defects is formed on the homoepitaxial layer.
The homoepitaxial layer is composed of, for example, a nitride semiconductor layer of the same type as the substrate. If the substrate is an AlN substrate, the homoepitaxial layer is also made of AlN.

The homoepitaxial layer has a thickness of, for example, several μm. Specifically, the thickness of the homoepitaxial layer is preferably thicker than 10 nm and thinner than 10 μm. When the thickness of the homoepitaxial layer is thicker than 10 nm, the crystallinity of the nitride semiconductor such as AlN becomes high. Furthermore, when the thickness of the homoepitaxial layer is thinner than 10 μm, cracks are less likely to occur in the homoepitaxial layer formed by crystal growth over the entire surface of the wafer.

(altered nitride semiconductor layer)
The modified nitride semiconductor layer is formed between the homoepitaxial layer on the substrate and the first conductivity type cladding layer, and is preferably formed over the entire surface of the substrate. The altered nitride semiconductor layer is a nitride semiconductor layer containing Al and Ga. The altered nitride semiconductor layer is formed of, for example, Al _x Ga _(1-x) N (0<x<1). The modified nitride semiconductor layer preferably has a thickness of 3 nm or more and 40 nm or less from the viewpoint of strain relaxation. In the altered nitride semiconductor layer, the stoichiometric ratio of group III atoms and group V atoms is not 1:1, that is, the content of nitrogen in the altered nitride semiconductor layer is too small relative to group III atoms, or Alternatively, the altered nitride semiconductor layer contains hydrogen in an amount of 1×10 ¹⁸ cm ⁻³ or more and 5×10 ¹⁹ cm ⁻³ or less. With these, strain can be concentrated on the altered nitride semiconductor layer and the strain applied to the entire layer formed above the altered nitride semiconductor layer can be alleviated. In other words, the modified nitride semiconductor layer also functions as a buffer layer. Thereby, the thickness of the first conductivity type cladding layer can be increased. As a result, resistance can be lowered and threshold voltage can be reduced. In addition, the relaxation of strain improves the luminous efficiency of carriers in the light emitting layer, making it possible to improve the luminous intensity and the oscillation threshold current density.
At this time, the stoichiometric ratio of group III atoms (e.g., Al and Ga) and group V atoms (e.g., N) may be changed from 1:1 or the hydrogen content may be changed by the production method described later. Can be done.

<First conductivity type cladding layer>
A first conductivity type cladding layer is formed on the substrate. Here, for example, the word "on" in the expression "the first conductivity type cladding layer is formed on the substrate" means that the first conductivity type cladding layer is formed on one surface of the substrate. do. Furthermore, the above expression also includes the case where another layer is further present between the substrate and the first conductivity type cladding layer. Regarding the relationships between other layers, the word "above" has the same meaning. For example, even when a second conductivity type cladding layer is formed on a first waveguide layer, which will be described later, via an electron block layer, it is said that "the second conductivity type cladding layer is formed on the first waveguide layer". included in the expression. In addition, in the description of this embodiment, "first conductivity type" and "second conductivity type" mean semiconductors exhibiting different conductivity types. For example, if one is n-type conductivity, , the other becomes p-type conductive.

The first conductivity type cladding layer is a nitride semiconductor layer containing Al and Ga. The first conductivity type cladding layer is formed of, for example, Al _a Ga _(1-a) N (0<a<1). This makes it possible to increase the crystallinity of the light emitting layer and improve the luminous efficiency when the light emitting layer is formed of a material that corresponds to the bandgap energy in the deep ultraviolet region. From the viewpoint of achieving high luminous efficiency, the nitride semiconductor constituting the first conductivity type cladding layer is preferably a mixed crystal of AlN and GaN. Furthermore, from the viewpoint of growing with complete strain on the substrate, the first conductivity type cladding layer is more preferably formed of Al _a Ga _(1-a) N (0.65<a≦0.9). .

The first conductivity type cladding layer may be a graded layer in which the Al composition increases as the distance from the substrate increases for the purpose of controlling longitudinal conductivity. In this case, the above-mentioned limitation on the Al composition can be set to an Al composition that is the average of the Al composition at a position in the film thickness direction within the first conductivity type cladding layer by the film thickness of the first conductivity type cladding layer.

When the first conductivity type cladding layer is an n-type conductivity semiconductor layer, it may contain impurities such as group V elements other than N such as P, As, and Sb, and C, H, F, O, Mg, and Si. However, the types of impurity elements are not limited to this. From the viewpoint of reducing electrical resistance and the difficulty of obtaining raw materials, the impurity contained in the first conductivity type cladding layer is preferably Si, and the impurity concentration is 5 × 10 ¹⁸ cm ^-3 or more and 5 × 10 ¹⁹ cm. ^-3 is preferred.
The first conductivity type cladding layer preferably has a layer thickness of 250 nm or more and 850 nm or less, from the viewpoint of lattice relaxation within the first conductivity type cladding layer and film resistance, and preferably has a layer thickness of 300 nm or more and 750 nm or less. It is more preferable that the layer thickness is 300 nm or more and 600 nm or less.

<Light-emitting layer>
The light emitting layer is a nitride semiconductor layer containing Al and Ga. The nitride semiconductor included in the light-emitting layer is preferably a mixed crystal of AlN or GaN, for example, from the viewpoint of achieving high luminous efficiency, and is formed of, for example, Al _b Ga _(1-b) N (0<b<1). Ru. In addition to N, the light-emitting layer may contain impurities such as group V elements other than N such as P, As, and Sb, and impurities such as C, H, F, O, Mg, and Si, but are not limited to this. .
Further, the light emitting layer can have a multiple quantum well structure or a single quantum well structure. The number of quantum well structures is preferably one to five, although it varies depending on the longitudinal conductivity of the first conductivity type cladding layer and the second conductivity type cladding layer (details will be described later).
Further, for the purpose of reducing the influence of crystal defects in the light emitting layer, a portion or all of the light emitting layer may contain elements such as Si, Sb, P, etc. in an amount of 1×10 ¹⁵ cm ⁻³ or more.

<Waveguide layer>
When the light emitting element of this embodiment is a laser diode, from the viewpoint of light confinement as a laser diode, it is formed above and below the light emitting layer so as to sandwich the light emitting layer, and has the effect of confining the light emitted from the light emitting layer within the light emitting layer. The waveguide layer may include a waveguide layer having the following. The waveguide layer includes a first waveguide layer disposed on the first conductivity type cladding layer side with respect to the light emitting layer, and a second waveguide layer disposed on the second conductivity type cladding layer side with respect to the light emission layer. Preferably, it is composed of two layers.
That is, the light emitting device of this embodiment includes, for example, a first waveguide layer that is disposed between a first conductivity type cladding layer and a light emitting layer to confine light to the light emitting layer, a second conductivity type cladding layer, and a light emitting layer. The second waveguide layer may be disposed between the light emitting layer and the light emitting layer to confine light to the light emitting layer.

From the viewpoint of optical confinement, the waveguide layer is preferably a nitride semiconductor containing Al and Ga that has a higher energy band gap than the light emitting layer. The waveguide layer preferably has an Al composition and film thickness that increase the electric field intensity distribution of light existing within the device and the overlap between the light emitting layers. From the viewpoint of carrier confinement in the light emitting layer, the light emitting layer is made of Al _b Ga _(1-b) N (0<b<1), and the waveguide layer is made of Al _c Ga _(1-c) N (0<c<1). ), it is more preferable that b<c and c≧b+0.05. For example, in the case of a light-emitting layer with an emission wavelength of 265 nm, b=0.52 and c is preferably 0.57 or more. Further, from the viewpoint of optical confinement and layer resistance, the total thickness of the waveguide layer is preferably 70 nm or more and 150 nm or less.

Although it is preferable that the Al compositions of the first waveguide layer and the second waveguide layer are uniform in the film thickness direction, the invention is not limited to this. In order to avoid light absorption by the metal (for example, the second electrode) existing above the second conductivity type cladding layer, which will be described later, the Al composition of the second waveguide layer is higher than the Al composition of the first waveguide layer. You can leave it there. For the same purpose, the second waveguide layer may be thicker than the first waveguide.
When the first waveguide layer is an n-type conductive semiconductor layer, in addition to N, group V elements other than N such as P, As, and Sb, H , C, O, F, Mg, Si, and other impurities may be mixed, but the present invention is not limited to this.

<Second conductivity type cladding layer>
The second conductivity type cladding layer is formed on the light emitting layer and is a nitride semiconductor layer containing Al and Ga and having second conductivity type conductivity. The second conductivity type cladding layer is formed of, for example, Al _d Ga _(1-d) N (0<d<1). Furthermore, when a waveguide layer (second waveguide layer) is provided on the light emitting layer, the second conductivity type cladding layer is formed on the waveguide layer (second waveguide layer). Thereby, the second conductivity type cladding layer can easily lattice match with the light emitting layer or the waveguide layer, and the threading dislocation density can be suppressed.

The second conductivity type cladding layer has sufficient conductivity to inject carriers (electrons or holes) into the light-emitting layer, and increases the overlap between the light-emitting layer and the electric field intensity distribution of the optical mode existing within the device. The conductivity type is not particularly limited as long as it is possible to increase the optical confinement (that is, increase optical confinement). The second conductivity type cladding layer may be, for example, Mg-doped p-type AlGaN.

In addition, when the second conductivity type cladding layer is a p-type conductivity semiconductor layer, impurities such as V group elements other than N such as P, As, and Sb, C, H, F, O, Mg, and Si are mixed. However, the types of impurity elements are not limited to this.
From the viewpoint of more efficiently injecting carriers into the light emitting layer, the second conductivity type cladding layer is sloped so that the Al composition e decreases as it moves away from the substrate, that is, the Al composition e decreases in the direction away from the upper surface of the substrate. A composition gradient layer (second conductivity type vertical conduction layer) formed of Al _e Ga _(1-e) N (0.1≦e≦1) and Al _f Ga _(1-f) N (0<f≦ 1) and a second conductivity type lateral conduction layer.
The second conductivity type vertical conduction layer and the second conductivity type horizontal conduction layer will be explained below.

(Second conductivity type vertical conduction layer)
The second conductivity type vertical conduction layer is a layer that constitutes a region of the second conductivity type cladding layer on the light emitting layer side.
The second conductivity type vertical conduction layer is a layer containing Al _e Ga _(1-e) N. The profile (gradient) of the Al composition e in the second conductivity type vertically conductive layer may decrease continuously or intermittently. Here, "intermittently decreasing" means that a part of the film of the second conductivity type vertical conduction layer includes a part where the Al composition e is the same (constant in the film thickness direction). . That is, the second conductivity type vertically conductive layer may include a portion where the Al composition e does not decrease in the direction away from the substrate, but does not include a portion where the Al composition e increases.

The thickness of the second conductivity type vertical conduction layer is preferably 500 nm or less from the viewpoint of lattice matching, more preferably 20 nm or more and 400 nm or less, and even more preferably 30 nm or more and 350 nm or less.
The second conductivity type vertical conduction layer contains impurities such as H, Mg, Be, Zn, Si, B, etc. in a region of the second conductivity type vertical conduction layer near the light emitting layer for the purpose of suppressing impurity diffusion. It is preferable that it is not doped (not intentionally mixed), that is, in an undoped state. Here, "undoped" means that the impurities mentioned above as elements are not intentionally supplied in the process of forming the target layer, but the element derived from the raw materials and manufacturing equipment is, for example, 1 × 10 ¹⁶ cm ^-3 This does not apply if it is mixed within the following range. Further, the undoped region of the second conductivity type vertical conduction layer includes at least the boundary with the light emitting layer (or the second waveguide layer when the second waveguide layer is provided), but the size thereof is not limited. For example, all regions of the second conductivity type vertical conduction layer may be in an undoped state. Further, as another example, 50% of the second conductivity type vertically conductive layer near the light emitting layer may be in an undoped state. Further, as another example, about 10% of the second conductivity type vertically conductive layer near the light emitting layer may be in an undoped state.

(Second conductivity type lateral conduction layer)
The second conductivity type horizontal conduction layer is a layer that constitutes a region of the second conductivity type cladding layer opposite to the light emitting layer, and is formed on the second conductivity type vertical conduction layer.
The second conductivity type lateral conduction layer is a layer containing Al _f Ga _(1-f) N (0<f≦1). Here, the Al composition f of the second conductivity type horizontal conduction layer on the surface facing the second conductivity type vertical conduction layer is preferably larger than the minimum value of the Al composition e of the second conductivity type vertical conduction layer.
The second conductivity type horizontal conduction layer may be intentionally mixed with impurities such as H, Mg, Be, Zn, Si, B, etc. for the purpose of controlling the vertical resistivity of the second conductivity type horizontal conduction layer. good. The amount of the impurity mixed is, for example, 1×10 ¹⁹ cm ⁻³ or more and 5×10 ²¹ cm ⁻³ depending on the amount of net electric field induced on the surface and inside of the second conductivity type lateral conduction layer. It may be.
The thickness of the second conductivity type horizontal conduction layer is preferably 20 nm or less, more preferably 10 nm or less, from the viewpoint of facilitating quantum transmission of carriers penetrating the second conductivity type horizontal conduction layer, and 5 nm or less. It is more preferable that it is the following.

When a second conductivity type contact layer, which will be described later, is provided on the second conductivity type lateral conduction layer, the Al composition at the interface of the second conductivity type lateral conduction layer with the second conductivity type contact layer is It is preferably smaller than the Al composition in the layer and completely strained with respect to the substrate. Such a second conductivity type lateral conduction layer has a negative net internal electric field accumulated on the surface and inside of the second conductivity type lateral conduction layer, and carriers are induced at the interface. Conductivity can be improved.

In this way, the second conductivity type vertical conduction layer generates carriers (for example, holes when the second conductivity type vertical conduction layer is formed of a p-type semiconductor) due to the polarization doping effect, and efficiently transfers carriers. It has a good effect of injecting into the active layer in the light emitting layer. Therefore, by providing the second conductivity type vertical conduction layer on the light emitting layer, the carrier injection efficiency of the light emitting element can be improved.

Furthermore, the second conductivity type lateral conduction layer has the effect of widening the carrier distribution, which is narrowed by the electric field concentrated below the electrode, in the lateral direction (within the plane of the second conductivity type lateral conduction layer). Due to this effect, the second conductivity type horizontal conduction layer can improve carrier injection efficiency into the light emitting layer similarly to the second conductivity type vertical conduction layer.

<Second conductivity type contact layer>
The semiconductor laminated portion of the light emitting device of this embodiment may further include a second conductivity type contact layer disposed on the second conductivity type cladding layer. The nitride semiconductor constituting the second conductivity type contact layer is preferably formed of, for example, GaN, AlN, or InN, or a mixed crystal containing them, and is more preferably a nitride semiconductor containing GaN.

The second conductivity type contact layer may contain impurities such as V group elements other than N such as P, As, and Sb, C, H, F, O, Mg, Si, and Be. In view of the versatility of the raw material gas, it is preferable that the impurity contained in the second conductivity type contact layer is Mg. From the viewpoint of reducing contact resistance, the Mg concentration is preferably 8×10 ¹⁹ cm ⁻³ or more and 5×10 ²¹ cm ⁻³ or less, and 5×10 ²⁰ cm ⁻³ or more and 5×10 ²¹ cm ⁻³ or less. It is more preferable that there be.

Further, the layer thickness of the second conductivity type contact layer is preferably 1 nm or more and 20 nm or less. The thinner the second conductivity type contact layer is, the more the carrier injection efficiency of the light emitting layer is improved, and the thicker the second conductivity type contact layer is, the lower the carrier injection efficiency is.

<Electronic block layer>
The semiconductor laminated portion of the light emitting layer of this embodiment may further include an electron blocking layer above the light emitting layer and having a larger band gap than the light emitting layer. The electron block layer may be provided, for example, on the light emitting layer, inside the second waveguide layer, between the second waveguide layer and the light emitting layer, or between the second waveguide layer and the second conductivity type vertical conduction layer. It can also be provided between.
The thickness of the electron block layer is preferably 30 nm or less, more preferably 20 nm or less so that carriers (holes) can easily quantum penetrate the electron block layer.

<Electrode>
The light emitting element can emit light or oscillate by injecting current through a second electrode placed on the second conductivity type cladding layer and a first electrode placed on the first conductivity type cladding layer. At this time, the first electrode is formed so as to be in electrical contact with the cladding layer of the first conductivity type, and the second electrode is formed so as to be in electrical contact with the contact layer of the second conductivity type.
For example, the first electrode can be placed on the back side of the substrate. Further, the first electrode is disposed on the first conductivity type cladding layer exposed by removing a layer above the first conductivity type cladding layer of the semiconductor laminated portion by, for example, chemical etching or dry etching. That is, the first electrode is arranged on a region of the first conductivity type cladding layer where no mesa structure is formed.

When the first conductivity type cladding layer is an n-type cladding layer, the first electrode is made of Al, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Co, Rh, Ir, Ni, Pd, Pt. , a metal such as Cu, Ag, Au, or Zr, a mixed crystal thereof, or a conductive oxide such as ITO or Ga ₂ O ₃ .
When the first conductivity type cladding layer is a p-type cladding layer, the first electrode is made of Ni, Au, Pt, Ag, Rh, Pd, Pt, Cu, Al, Ti, Zr, Hf, V, Nb, Ta, Cr. , a metal such as Mo, W, Co, Ir, and Zr, a mixed crystal thereof, or a conductive oxide such as ITO or Ga ₂ O ₃ .

When the second conductivity type cladding layer is an n-type cladding layer, the second electrode is made of Al, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Co, Rh, Ir, Ni, Pd, Pt. , a metal such as Cu, Ag, Au, or Zr, a mixed crystal thereof, or a conductive oxide such as ITO or Ga ₂ O ₃ .
When the second conductivity type cladding layer is a p-type cladding layer, the second electrode is made of Ni, Au, Pt, Ag, Rh, Pd, Pt, Cu, Al, Ti, Zr, Hf, V, Nb, Ta, Cr. , a metal such as Mo, W, Co, Ir, and Zr, a mixed crystal thereof, or a conductive oxide such as ITO or Ga ₂ O ₃ .

The arrangement area and shape of the first electrode and the second electrode are different from each other in the first conductivity type cladding layer and the second conductivity type cladding layer (or the second conductivity type contact layer when the second conductivity type contact layer is provided). There is no limitation as long as electrical contact is obtained.

(1.2) Method for manufacturing light emitting device The light emitting device of this embodiment is manufactured through a process of forming each layer on a substrate.

(Formation of substrate)
The substrate is formed by a general substrate growth method such as a sublimation method, a vapor phase epitaxy method such as a hydride vapor phase epitaxy (HVPE) method, and a liquid phase epitaxy method.

(Formation of semiconductor stack)
Each layer of the semiconductor stack formed on the substrate is formed using, for example, molecular beam epitaxy (MBE), hydride vapor phase epitaxy (HVPE), or metal organic chemical vapor deposition (MOCVD). It can be formed by a method or the like.
Here, among the layers formed on the substrate, the nitride semiconductor layer is made of, for example, an Al raw material containing trimethylaluminum (TMAl), a Ga raw material containing trimethylgallium (TMGa) or triethylgallium (TEGa), or ammonia ( It can be formed using an N raw material containing NH ₃ ).

The altered nitride semiconductor layer is formed by heat treating a nitride buffer layer containing Al formed on a substrate. Specifically, first, an AlGaN layer is formed as a buffer layer on a substrate. The buffer layer is heat treated alternately in hydrogen and _NH3 . In this process, nitrogen in the buffer layer is desorbed, resulting in a nitrogen-deficient state, and the stoichiometric ratio of group III atoms and group V atoms is not 1:1, resulting in a nitride semiconductor with a different stoichiometric composition. A layer is formed.
As a result, when forming a first conductivity type cladding layer, a light emitting layer, etc. on a nitride semiconductor layer, a strong strain is applied to the modified nitride semiconductor layer having a different stoichiometric composition. As a result, the strain applied to the light emitting layer is reduced, the light emission efficiency of carriers is improved, and the light emission intensity is improved.

From the viewpoint of nitrogen removal, the reactor pressure during heat treatment is preferably 10 mbar or more and 50 mbar or less, more preferably 10 mbar or more and 40 mbar or less. Further, the temperature of the heat treatment is preferably 1200°C or more and 1400°C or less, more preferably 1200°C or more and 1350°C or less. The treatment time is preferably 50 minutes or more and 15 minutes or less.

A first conductivity type cladding layer containing a first conductivity type nitride semiconductor is formed on the nitride semiconductor layer formed by heat treatment. Next, a light emitting layer made of a nitride semiconductor (AlGaN or the like) including one or more quantum wells is formed on the first conductivity type cladding layer, and a second conductivity type cladding layer is formed on the light emitting layer.
If necessary, waveguide layers made of a nitride semiconductor such as AlGaN may be formed above and below the light emitting layer. Further, an intermediate layer made of a nitride semiconductor such as AlGaN may be formed between the second conductivity type cladding layer and the waveguide, or a second conductivity type nitride semiconductor layer containing GaN or the like may be formed on the second conductivity type cladding layer. A contact layer may be provided, or an electron blocking layer may be formed above the light emitting layer.

A light emitting element is manufactured through a step (mesa structure forming step) of removing unnecessary portions of each layer of a semiconductor stack formed on a substrate by etching. The unnecessary portions of each layer of the semiconductor stack can be removed by, for example, inductively coupled plasma (ICP) etching.
In the mesa structure forming step, unnecessary portions of each layer of the conductive layered portion are removed by etching, thereby exposing a portion of the first conductivity type cladding layer.

(Formation of electrode)
Further, the light emitting element can be manufactured through a process of forming electrodes. Electrodes such as the first electrode and the second electrode can be formed by various methods of depositing metal by electron beam evaporation (EB), such as resistance heating evaporation, electron gun evaporation, or sputtering. is not limited. Each electrode may be formed of a single layer or may be formed of a plurality of laminated layers. Further, each electrode may be subjected to heat treatment in an oxygen, nitrogen, or air atmosphere after forming the layer.
Finally, the substrate on which each layer has been formed through the steps described above is divided into individual pieces by dicing to manufacture light emitting elements.

Specifically, a first electrode is formed on the surface of the first conductivity type cladding layer. Further, the second electrode is formed on the uppermost layer (for example, a second conductivity type cladding layer) of a mesa structure that is partially formed in the semiconductor stack.
In this way, according to the method for manufacturing a light emitting device according to the present embodiment, carrier injection efficiency can be increased and emission intensity can be increased.

2. Method for Measuring Physical Properties, etc. of Light-Emitting Element The physical properties, etc. of the above-mentioned light-emitting element can be measured as follows.

(Method for measuring layer thickness)
The layer thickness of each layer that makes up the light emitting element is measured by cutting out a predetermined cross section perpendicular to the substrate, observing this cross section with a transmission electron microscope (TEM), and using the length measurement function of the TEM. can. As a measurement method, first, a cross section perpendicular to the main surface of the substrate of the light emitting element is observed using a TEM. Specifically, for example, the observation width is a range of 2 μm or more in a direction parallel to the main surface of the substrate in a TEM image showing a cross section perpendicular to the main surface of the substrate of the light emitting element. In this observation width range, a contrast is observed at the interface between two layers with different compositions, so the thickness up to this interface is observed in a continuous observation area with a width of 200 nm. The layer thickness of each layer can be obtained by calculating the average value of the thickness of each layer included in this 200 nm wide observation region from five points arbitrarily extracted from the above-mentioned observation width of 2 μm or more.

(Measurement of impurity concentration and doping concentration)
The concentration of dopants and impurities contained in each layer constituting a light emitting element can be measured by secondary ion mass spectrometry (SIMS).
When measuring the concentration of dopants and impurities contained in each layer by SIMS after processing into a device, the measurement can be performed with the electrodes removed by chemical etching or physical polishing. Furthermore, the concentration of dopants and impurities contained in each layer can also be measured by sputtering from the substrate side on which no electrodes are formed.
Specifically, SIMS measurement is performed under measurement conditions provided by Evans Analytical Group (EAG). A cesium (Cs) ion beam with an energy of 14.5 keV is used to sputter the sample during measurement.

(Method for measuring atomic concentration in each layer)
A method for measuring the atomic concentration contained in each layer constituting a light emitting element includes reciprocal space mapping (RSM) using X-ray diffraction (XRD). Specifically, by analyzing reciprocal lattice mapping data near the diffraction peak obtained using the asymmetric surface as the diffraction surface, the lattice relaxation rate and Al composition with respect to the base can be obtained. Examples of the diffraction plane include the (10-15) plane and the (20-24) plane.
In addition, for layers and regions where sufficient reflection intensity cannot be obtained by XRD, such as light-emitting layers, gradient layers, and hillocks formed in each layer, X-ray photoelectron spectroscopy (XPS), energy-dispersive It can be measured by energy dispersive X-ray spectroscopy (EDX) and electron energy-loss spectroscopy (EELS).

In EELS, the composition of a sample is analyzed by measuring the energy lost when an electron beam passes through the sample. Specifically, for example, the energy loss spectrum of the intensity of the transmitted electron beam is measured and analyzed in a thin sectioned sample used in TEM observation or the like. Then, by utilizing the fact that the peak position that appears near the energy loss amount of 20 eV changes depending on the composition of each layer, the composition can be determined from the peak position.
In the same manner as the layer thickness calculation method using TEM observation described above, the average value of the Al composition in the observation width of 200 nm is calculated from five points arbitrarily extracted from the observation area of 2 μm or more to obtain the Al composition of each layer.

In EDX, characteristic X-rays generated by an electron beam are measured and analyzed in a thin sectioned sample used in the above-mentioned TEM observation and the like. In the same manner as the layer thickness calculation method using TEM observation described above, the average value of the Al composition in the observation width of 200 nm is calculated from five points arbitrarily extracted from the observation area of 2 μm or more to obtain the Al composition of each layer.

In XPS, evaluation in the depth direction is possible by performing XPS measurement while performing sputter etching using an ion beam. Although Ar+ is generally used as the ion beam, other ion species such as Ar cluster ions may be used as long as they can be irradiated with an etching ion gun mounted on the XPS apparatus. The XPS peak intensities of Al, Ga, and N are measured and analyzed to obtain the depth distribution of Al composition in each layer. Instead of sputter etching, the light emitting element may be obliquely polished so that a cross section perpendicular to the main surface of the substrate is enlarged and exposed, and the exposed cross section may be measured by XPS.

In particular, when measuring the stoichiometric ratio of the altered nitride semiconductor layer, it is preferable to use XPS measurement.
The composition of each layer can be measured not only by XPS but also by Auger Electron Spectroscopy (AES). In this case, the composition can be measured by performing measurement using Auger electron spectroscopy on a cross section exposed by sputter etching or oblique polishing. The composition of each layer can also be measured by SEM-EDX measurement on a cross section exposed by oblique polishing.

(Application field of light emitting device)
The light emitting device according to the present disclosure is applicable to, for example, devices in the medical/life science field, the environment field, the industry/industrial field, the lifestyle/home appliance field, the agricultural field, and other fields. Light-emitting elements are used in synthesis and decomposition equipment for drugs or chemical substances, sterilization equipment for liquids, gases, and solids (containers, foods, medical equipment, etc.), cleaning equipment for semiconductors, etc., surface modification equipment for films, glass, metals, etc., and semiconductors.・FPD (Flat Panel Display), PCB (Printed Wiring Board), exposure equipment for manufacturing other electronic products, printing/coating equipment, adhesion/sealing equipment, transfer/forming equipment for films, patterns, mockups, etc., banknotes/scratches - Applicable to measurement and inspection equipment for blood, chemical substances, etc.

Examples of liquid sterilizers include automatic ice makers, ice trays and ice storage containers in refrigerators, water supply tanks for ice makers, cold water tanks, hot water tanks, and flow channels for freezers, ice makers, humidifiers, dehumidifiers, and water servers. Piping, stationary water purifiers, portable water purifiers, water heaters, water heaters, wastewater treatment equipment, disposers, toilet drain traps, washing machines, dialysis water sterilization modules, peritoneal dialysis connector sterilizers, disaster water storage systems, etc. It can be mentioned, but it is not limited to this.

Examples of gas sterilizers include air purifiers, air conditioners, ceiling fans, floor or bedding vacuum cleaners, futon dryers, shoe dryers, washing machines, clothes dryers, indoor germicidal lights, and storage ventilation. Examples include, but are not limited to, systems, shoe boxes, chests of drawers, etc.
Examples of solid sterilizers (including surface sterilizers) include vacuum packers, belt conveyors, hand tool sterilizers for medical, dental, barber and beauty salons, toothbrushes, toothbrush holders, chopstick cases, cosmetic pouches, Examples include, but are not limited to, drain covers, toilet bowl washers, toilet bowl lids, etc.

3. Specific Example of Light-Emitting Element Hereinafter, the light-emitting element of this embodiment will be described in more detail with reference to FIGS. 1 and 2. Note that the detailed configuration of each layer in each embodiment below is as described above.

(3.1) First Embodiment FIG. 1 is a schematic cross-sectional view showing a configuration example of a laser diode 1, which is an example of a light emitting element according to this embodiment. As shown in FIG. 1, the laser diode 1 includes a substrate 11, a semiconductor stack 10 disposed on the substrate 11, a first electrode 12, and a second electrode 13. The semiconductor stack 10 includes a modified nitride semiconductor layer 101, a first conductivity type cladding layer 102 having an n-type conductivity, a first waveguide layer 103, a light emitting layer 104, a second waveguide layer 105, and a p-type cladding layer 102. The contact layer 107 includes a second conductivity type cladding layer 106 and a contact layer 107 having the same conductivity type.

(3.2) Second Embodiment FIG. 2 is a schematic cross-sectional view showing a configuration example of a light emitting diode 2, which is an example of a light emitting element according to this embodiment. As shown in FIG. 2, the light emitting diode 2 includes a substrate 11, a semiconductor stack 20 disposed on the substrate, a first electrode 12, and a second electrode 13. The semiconductor stack 20 includes a modified nitride semiconductor layer 201, a first conductivity type cladding layer 202 having an n-type conductivity type, a light emitting layer 203, an electron block layer 204, and a second conductivity type cladding layer 202 having a p-type conductivity type. It includes a conductive cladding layer 205 and a contact layer 206.

4. Effects The above-described light-emitting element and method for manufacturing a light-emitting element have the following effects.

(1) In the method for manufacturing a light emitting device of the present disclosure, a buffer layer is formed on a substrate, and a modified nitride semiconductor layer is formed by alternately performing heat treatment in hydrogen and NH ₃ . In this step, nitrogen in the buffer layer is desorbed, resulting in a nitrogen-deficient state, and the stoichiometric composition of group III atoms and group V atoms in the altered nitride semiconductor layer is no longer 1:1. Due to the formation of nitride semiconductor layers with different stoichiometric compositions, the strain that occurs when forming the first conductivity type cladding layer, light-emitting layer, etc., formed thereon is caused by altered nitride semiconductor layers with different stoichiometric compositions. A strong voltage is applied to the physical semiconductor layer. In addition, in this step, the amount of hydrogen contained in the altered nitride semiconductor layer can be reduced to 1×10 ¹⁸ cm ^-3 or more and 5×10 ¹⁹ cm ^{-3 or} less, which alleviates the strain applied to the entire altered nitride semiconductor layer. can be done.
This reduces the strain applied to the light-emitting layer and improves the light-emitting efficiency of carriers, making it possible to realize continuous oscillation of the laser diode and a sterilization function in a short time by increasing the light-emission intensity of the light-emitting diode.

(2) A light emitting device of the present disclosure includes a nitride semiconductor substrate containing Al, a semiconductor stacked section placed on the nitride semiconductor substrate, the semiconductor stacked section placed on the substrate, and a substrate; a first conductivity type cladding layer including a first conductivity type nitride semiconductor layer; a light emitting layer disposed on the first conductivity type cladding layer and formed of a nitride semiconductor including one or more quantum wells; a second conductivity type cladding layer disposed on the substrate and including a second conductivity type nitride semiconductor layer, and between the substrate and the first conductivity type cladding layer, group III atoms and group V atoms are arranged. It is preferable to provide an altered nitride semiconductor layer whose stoichiometric ratio is not 1:1 or an altered nitride semiconductor layer containing hydrogen in an amount of 1×10 ¹⁸ cm ⁻³ or more and 5×10 ¹⁹ cm ^{−3 or} less.
As a result, the strain applied to the entire layer formed above the altered nitride semiconductor layer can be relaxed, so the thickness of the first conductivity type cladding layer can be increased. As a result, resistance can be lowered and threshold voltage can be reduced. In addition, the relaxation of strain improves the luminous efficiency of carriers in the light emitting layer, making it possible to improve the luminous intensity and the oscillation threshold current density.

(3) In the light emitting device of the present disclosure, it is preferable that the modified nitride semiconductor layers having different stoichiometric ratios contain too little nitrogen relative to Group III atoms.
This makes it possible to alleviate the strain applied to the entire layer formed above the altered nitride semiconductor layer. Thereby, the thickness of the first conductivity type cladding layer can be increased. As a result, resistance can be lowered and threshold voltage can be reduced. In addition, the relaxation of strain improves the luminous efficiency of carriers in the light emitting layer, making it possible to improve the luminous intensity and the oscillation threshold current density.

(4) In the light emitting device of the present disclosure, the modified nitride semiconductor layers having different stoichiometric ratios preferably have a thickness of 3 nm or more and 40 nm or less.
This makes it possible to alleviate the strain applied to the entire layer formed above the altered nitride semiconductor layer. Thereby, the thickness of the first conductivity type cladding layer can be increased. As a result, resistance can be lowered and threshold voltage can be reduced. In addition, the relaxation of strain improves the luminous efficiency of carriers in the light emitting layer, making it possible to improve the luminous intensity and the oscillation threshold current density.

(5) In the light emitting device of the present disclosure, the modified nitride semiconductor layers having different stoichiometric ratios are preferably AlGaN.
Thereby, strain applied to the entire layer formed above the altered nitride semiconductor layer can be alleviated. Thereby, the thickness of the first conductivity type cladding layer can be increased. As a result, resistance can be lowered and threshold voltage can be reduced. In addition, the relaxation of strain improves the luminous efficiency of carriers in the light emitting layer, making it possible to improve the luminous intensity and the oscillation threshold current density.

(6) In the light emitting device of the present disclosure, the nitride semiconductor substrate is preferably an AlN single crystal substrate.
This reduces the difference in lattice constant between the substrate and the nitride semiconductor layer formed on the upper side of the substrate, and by growing the nitride semiconductor layer in a lattice-matched system, it is possible to reduce threading dislocations and improve stability. A high nitride semiconductor layer can be formed.

(7) In the light emitting device of the present disclosure, the first conductivity type cladding layer is preferably formed of Al _a Ga _1-a N (0.65<a≦0.90).
This makes it possible to grow with complete strain and achieve high luminous efficiency.

(8) In the light emitting device of the present disclosure, the first conductivity type cladding layer preferably has a thickness of 250 nm or more and 800 nm or less.
As a result, a nitride semiconductor laminate that does not relax can be obtained, and the luminous efficiency can be improved. Furthermore, membrane resistance is reduced, and threshold voltage can be reduced.

(9) The light emitting device of the present disclosure includes a first waveguide layer disposed between the first conductivity type cladding layer and the light emitting layer, and a first waveguide layer disposed between the second conductivity type cladding layer and the light emitting layer. 2 waveguide layers.
This improves the effect of confining light in the light emitting layer and improves the light emitting efficiency.

(10) The light emitting device of the present disclosure includes a second conductivity type contact layer disposed on the second conductivity type cladding layer and formed of a nitride semiconductor containing GaN, the second conductivity type cladding layer comprising Al a second conductive film containing _b Ga _1-b N (0.1≦b≦1), having a composition gradient in which the Al composition b decreases as it moves away from the nitride semiconductor substrate, and having a film thickness of less than 0.5 μm; It is preferable to have a vertical conductive layer of type 2 and a horizontal conductive layer of second conductivity type containing Al _c Ga _1-c N (0<c≦1).
This makes it possible to more efficiently inject carriers into the light-emitting layer, resulting in improved light-emitting efficiency.

Examples and comparative examples of the present disclosure will be described below.

<Example 1>
A laser diode was manufactured by the manufacturing method shown below.
A (0001) plane AlN single crystal substrate with a thickness of 550 μm was used as the substrate.
Next, an AlN layer, which is a homoepitaxial layer, was formed on the substrate. The AlN layer was formed to a thickness of 500 nm in an environment of 1200°C. At this time, the ratio (V/III ratio) between the supply rate of the group III element raw material gas and the supply rate of the nitrogen raw material gas was set to 50. The growth rate of the AlN layer at this time was 0.5 μm/hr. Further, trimethylaluminum (TMAl) was used as an Al raw material. Furthermore, ammonia (NH ₃ ) was used as the N raw material.

On this substrate, an AlGaN layer (Al: 95%, ie, an Al _0.95 Ga _0.05 N layer) was formed as a buffer layer. The AlGaN layer was formed to a thickness of 20 nm at a temperature of 1080° C., a vacuum degree of 50 mbar, and a V/III ratio of 4000. The growth rate of the AlGaN layer at this time was 0.4 μm/hr. Further, trimethylaluminum (TMAl) was used as an Al raw material. Further, triethyl gallium (TEGa) was used as a Ga raw material. Furthermore, ammonia (NH ₃ ) was used as the N raw material. This AlGaN layer was annealed using a MOCVD apparatus. Two sets of annealing treatments were performed in an environment of 1250° C., one set being annealing for 5 minutes in an NH ₃ atmosphere and another for 5 minutes in an H ₂ atmosphere. Further, the vacuum degree of the chamber in which the annealing was performed was set to 25 mbar. This annealing treatment formed a modified nitride semiconductor layer in which the stoichiometric ratio of Group III atoms to Group V atoms was not 1:1.

A first conductivity type cladding layer was formed on the altered nitride semiconductor layer formed as described above in which the stoichiometric ratio of group III atoms and group V atoms was not 1:1. The first conductivity type cladding layer was an n-type AlGaN layer (Al: 75%, that is, an Al _0.75 Ga _0.25 N layer) using Si as a dopant impurity. The first conductivity type cladding layer was formed to have a thickness of 400 nm at a temperature of 1080° C., a vacuum degree of 50 mbar, and a V/III ratio of 4000. The growth rate of the first conductivity type cladding layer at this time was 0.4 μm/hr. Further, trimethylaluminum (TMAl) was used as an Al raw material. Further, triethyl gallium (TEGa) was used as a Ga raw material. Furthermore, ammonia (NH ₃ ) was used as the N raw material. Moreover, monosilane (SiH ₄ ) was used as a Si raw material.

Subsequently, an n-type waveguide layer, which is a first waveguide layer, was formed on the first conductivity type cladding layer. The n-type waveguide layer was an n-type AlGaN layer (Al: 63%, that is, an Al _0.63 Ga _0.37 N layer) using Si as a dopant impurity. The n-type waveguide layer was formed to have a thickness of 60 nm at a temperature of 1080° C., a vacuum degree of 50 mbar, and a V/III ratio of 4000. The growth rate of the n-type waveguide layer at this time was 0.35 μm/hr. Further, trimethylaluminum (TMAl) was used as an Al raw material. Further, triethyl gallium (TEGa) was used as a Ga raw material. Furthermore, ammonia (NH ₃ ) was used as the N raw material.

Subsequently, a light emitting layer was formed on the n-type waveguide layer. The light-emitting layer was formed by forming a film to have a multi-quantum well structure in which quantum well layers and barrier layers were laminated three times. Here, the quantum well layer was an AlGaN layer (Al: 52%, ie, an Al _0.52 Ga _0.48 N layer) having a thickness of 3.0 nm. Further, the barrier layer having a thickness of 6.0 nm was an AlGaN layer (Al: 63%, that is, an Al _0.63 Ga _0.37 N layer).
The light emitting layer was formed under the conditions that the degree of vacuum was set at 50 mbar and the V/III ratio was set at 4000. The growth rate of the quantum well layer at this time was 0.18 μm/hr. Further, the growth rate of the barrier layer was 0.15 μm/hr.

Subsequently, a p-type waveguide layer, which is a second waveguide layer, was formed on the light emitting layer. The p-type waveguide layer was an AlGaN layer (Al: 63%, ie, an Al _0.63 Ga _0.37 N layer) containing no dopant. The p-type waveguide layer was formed to have a thickness of 60 nm at a temperature of 1080° C., a vacuum degree of 50 mbar, and a V/III ratio of 4000. The growth rate of the p-type waveguide layer at this time was 0.35 μm/hr. Further, trimethylaluminum (TMAl) was used as an Al raw material. Further, triethyl gallium (TEGa) was used as a Ga raw material.

Subsequently, a second conductivity type cladding layer was formed on the p-type waveguide layer. The second conductivity type cladding layer has a laminated structure including a second conductivity type vertical conduction layer and a second conductivity type horizontal conduction layer, and is a graded layer having a gradient Al composition ratio. The second conductivity type vertical conduction layer was an AlGaN layer having a thickness of 20 nm and having an Al composition distribution in the direction away from the substrate, varying from Al=0.63 to 1.0. Further, the second conductivity type lateral conduction layer was a p-type AlGaN layer having a layer thickness of 320 nm and having an Al composition distribution in the direction away from the substrate and varying from Al=1.0 to 0.7. The second conductivity type cladding layer was formed at a temperature of 1080° C., a vacuum degree of 50 mbar, and a V/III ratio of 4000. The growth rate of the second conductivity type cladding layer at this time was 0.3 to 0.5 μm/hr. Further, trimethylaluminum (TMAl) was used as an Al raw material. Further, triethyl gallium (TEGa) was used as a Ga raw material.

Subsequently, a p-type contact layer, which is a second conductivity type contact layer, was formed on the second conductivity type cladding layer. Here, the p-type contact layer was formed of an AlGaN layer and a GaN layer. The AlGaN layer was a p-type nitride semiconductor layer with a thickness of 30 nm, using Mg as a dopant impurity, and having an Al composition distribution in the direction away from the substrate, varying from Al=0.7 to 0.4. Further, the GaN layer was formed of GaN (ie, Al: 0%) having a thickness of 10 nm.
The second conductivity type contact layer was formed at a temperature of 950° C., a vacuum degree of 150 mbar, and a V/III ratio of 3650. The growth rate of the second conductivity type contact layer at this time was 0.2 μm/hr.

Cross-sectional TEM observation and XPS measurement were performed on the nitride semiconductor laminate obtained as described above. As a result, a layer with a different contrast of 20 nm was observed at the boundary between the substrate and the first conductivity type cladding layer from the cross-sectional TEM measurement. XPS measurements showed that the stoichiometric ratio of this layer was more group III atoms than nitrogen. Furthermore, the film thickness was also consistent with the cross-sectional TEM measurement. From the SIMS measurement, 5.0×10 ¹⁸ cm ⁻³ of hydrogen was detected in this layer.
In the manner described above, a semiconductor laminated portion was formed on the AlN substrate. When a reciprocal lattice mapping measurement was performed using XRD on this semiconductor stack, it was found that the semiconductor stack had undergone pseudomorphic growth without relaxation up to the second conductivity type contact layer.

The semiconductor stack formed as described above was annealed at 700° C. for 10 minutes or more in an N ₂ atmosphere to further reduce the resistance of the second conductivity type contact layer. By performing dry etching with a gas containing Cl ₂ using ICP, a mesa structure in which the first conductivity type cladding layer was exposed was formed.
The mesa structure formed had a length of 700 μm in the <1-100> direction and a length of 40 μm in the <11-20> direction. Here, the length of the mesa structure in the <1-100> direction is the distance between the end faces of the resonator mirrors in plan view, and the length in the <11-20> direction is the distance between the side surfaces of the mesa structure. It is.

On the second conductivity type contact layer in the mesa structure, a plurality of electrode metal regions were formed by sequentially forming Ni and Au films in a rectangular shape elongated in the <1-100> direction to form a p-type second electrode. At this time, the width of the second electrode was 5 μm, and the length was 600 μm or more. In addition, in the region where the n-type cladding layer of the mesa structure is exposed, a plurality of electrode metal regions are formed by sequentially forming V, Al, Ni, Ti, and Au in a long rectangular shape in the <1-100> direction. This was used as the first electrode of the mold. The first electrode and the second electrode were annealed at 550° C. for 60 seconds in a nitrogen atmosphere using an RTA apparatus.

Furthermore, the substrate was divided into stripes by multiple cleavages parallel to the <11-20> direction within the electrode metal region, thereby forming individual laser diodes. The length of the mesa structure after division in the <1-100> direction was 600 μm.
When the laser diode thus obtained was subjected to current-edge emission intensity measurement by current injection, the threshold voltage was 12 V and the oscillation threshold current was 7.5 kA/cm ² .

<Example 2>
The AlGaN annealing process was performed in an environment of 1220°C, and the thickness of the altered nitride semiconductor layer in which the stoichiometric ratio of group III atoms and group V atoms was not 1:1 was 5 nm, which was detected by SIMS measurement. A laser diode of Example 2 was formed in the same manner as Example 1 except that the hydrogen content of the modified nitride semiconductor layer was 2.0×10 ¹⁸ cm ⁻³ . When the laser diode thus obtained was subjected to current-edge emission intensity measurement by current injection, the threshold voltage was 12 V and the oscillation threshold current was 8.5 kA/cm ² .

<Example 3>
The AlGaN annealing process was performed in an environment of 1300°C, and the thickness of the altered nitride semiconductor layer in which the stoichiometric ratio of group III atoms and group V atoms was not 1:1 was 35 nm, which was detected by SIMS measurement. A laser diode of Example 3 was formed in the same manner as Example 1 except that the hydrogen content of the modified nitride semiconductor layer was 7.0×10 ¹⁸ cm ⁻³ . When the laser diode thus obtained was subjected to current-edge emission intensity measurement by current injection, the threshold voltage was 12 V and the oscillation threshold current was 8.5 kA/cm ² .

<Example 4>
AlGaN was annealed in an environment of 1330°C, and the thickness of the altered nitride semiconductor layer in which the stoichiometric ratio of group III atoms and group V atoms was not 1:1 was 40 nm, which was detected by SIMS measurement. A laser diode of Example 4 was formed in the same manner as Example 1 except that the hydrogen content of the modified nitride semiconductor layer was 1.0×10 ¹⁹ cm ⁻³ . When the laser diode thus obtained was subjected to current-edge emission intensity measurement by current injection, the threshold voltage was 12 V and the oscillation threshold current was 9.0 kA/cm ² .

<Example 5>
The AlGaN annealing process was performed in an environment of 1380°C, and the thickness of the altered nitride semiconductor layer in which the stoichiometric ratio of group III atoms and group V atoms was not 1:1 was 50 nm, which was detected by SIMS measurement. A laser diode of Example 5 was formed in the same manner as Example 1 except that the hydrogen content of the modified nitride semiconductor layer was 3.0×10 ¹⁹ cm ⁻³ . When the laser diode thus obtained was subjected to current-edge emission intensity measurement by current injection, the threshold voltage was 12 V and the oscillation threshold current was 10.5 kA/cm ² .

<Example 6>
The AlGaN annealing process was carried out in a vacuum environment of 15 mbar, and the thickness of the altered nitride semiconductor layer in which the stoichiometric ratio of group III atoms and group V atoms was not 1:1 was 25 nm, and SIMS measurement revealed that the thickness of the altered nitride semiconductor layer was 25 nm. A laser diode of Example 6 was formed in the same manner as Example 1 except that the detected hydrogen content of the altered nitride semiconductor layer was 5.0×10 ¹⁸ cm ⁻³ . When the laser diode thus obtained was subjected to current-edge emission intensity measurement by current injection, the threshold voltage was 12 V and the oscillation threshold current was 8.0 kA/cm ² .

<Example 7>
The AlGaN annealing process was performed in a vacuum environment of 40 mbar, and the thickness of the altered nitride semiconductor layer in which the stoichiometric ratio of group III atoms and group V atoms was not 1:1 was 10 nm, and SIMS measurement revealed that the thickness of the altered nitride semiconductor layer was 10 nm. A laser diode of Example 7 was formed in the same manner as Example 1 except that the detected hydrogen content of the altered nitride semiconductor layer was 5.0×10 ¹⁸ cm ⁻³ . When the laser diode thus obtained was subjected to current-edge emission intensity measurement by current injection, the threshold voltage was 12 V and the oscillation threshold current was 8.0 kA/cm ² .

<Example 8>
The process was carried out in the same manner as in Example 1, except that the film thickness of the first conductivity type cladding layer was 450 nm, and the hydrogen content of the altered nitride semiconductor layer detected by SIMS measurement was 5.0 × 10 ¹⁸ cm ^-3 . A laser diode of Example 8 was formed. When the laser diode thus obtained was subjected to current-edge emission intensity measurement by current injection, the threshold voltage was 11.5 V and the oscillation threshold current was 7.5 kA/cm ² .

<Example 9>
The process was carried out in the same manner as in Example 1, except that the film thickness of the first conductivity type cladding layer was 350 nm, and the hydrogen content of the altered nitride semiconductor layer detected by SIMS measurement was 5.0 × 10 ¹⁸ cm ^-3 . A laser diode of Example 9 was formed. When the laser diode thus obtained was subjected to current-edge emission intensity measurement by current injection, the threshold voltage was 12.5 V and the oscillation threshold current was 7.5 kA/cm ² .

<Example 10>
A light emitting diode was manufactured by the manufacturing method shown below.
A (0001) plane AlN single crystal substrate with a thickness of 550 μm was used as the substrate.
Next, an AlN layer, which is a homoepitaxial layer, was formed on the substrate. The AlN layer was formed to a thickness of 500 nm in an environment of 1200°C. At this time, the ratio (V/III ratio) between the supply rate of the group III element raw material gas and the supply rate of the nitrogen raw material gas was set to 50. The growth rate of the AlN layer at this time was 0.5 μm/hr. Further, trimethylaluminum (TMAl) was used as an Al raw material. Furthermore, ammonia (NH ₃ ) was used as the N raw material.

An AlGaN layer (Al: 95%, ie, an Al _0.95 Ga _0.05 N layer) was formed on this substrate. The AlGaN layer was formed to a thickness of 20 nm at a temperature of 1080° C., a vacuum degree of 50 mbar, and a V/III ratio of 4000. The growth rate of the AlGaN layer at this time was 0.4 μm/hr. Further, trimethylaluminum (TMAl) was used as an Al raw material. Further, triethyl gallium (TEGa) was used as a Ga raw material. Furthermore, ammonia (NH ₃ ) was used as the N raw material. This AlGaN layer was annealed using a MOCVD apparatus. Two sets of annealing treatments were performed in an environment of 1250° C., one set being annealing for 5 minutes in an NH ₃ atmosphere and another for 5 minutes in an H ₂ atmosphere. Further, the vacuum degree of the chamber in which the annealing was performed was set to 25 mbar. This annealing treatment formed a modified nitride semiconductor layer in which the stoichiometric ratio of Group III atoms to Group V atoms was not 1:1.

A first conductivity type cladding layer was formed on the altered nitride semiconductor layer formed as described above in which the stoichiometric ratio of group III atoms and group V atoms was not 1:1. The first conductivity type cladding layer was an n-type AlGaN layer (Al: 75%, that is, an Al _0.75 Ga _0.25 N layer) using Si as a dopant impurity. The first conductivity type cladding layer was formed to have a thickness of 600 nm at a temperature of 1080° C., a vacuum degree of 50 mbar, and a V/III ratio of 4000. The growth rate of the first conductivity type cladding layer at this time was 0.4 μm/hr. Further, trimethylaluminum (TMAl) was used as an Al raw material. Further, triethyl gallium (TEGa) was used as a Ga raw material. Furthermore, ammonia (NH ₃ ) was used as the N raw material. Moreover, monosilane (SiH ₄ ) was used as a Si raw material.

Subsequently, a light emitting layer was formed on the first conductivity type cladding layer. The light-emitting layer was formed by forming a film to have a multi-quantum well structure in which quantum well layers and barrier layers were laminated three times. Here, the quantum well layer was an AlGaN layer (Al: 52%, ie, an Al _0.52 Ga _0.48 N layer) having a thickness of 3.0 nm. Further, the barrier layer having a thickness of 6.0 nm was an AlGaN layer (Al: 63%, that is, an Al _0.63 Ga _0.37 N layer).
The light emitting layer was formed under the conditions that the degree of vacuum was set at 50 mbar and the V/III ratio was set at 4000. The growth rate of the quantum well layer at this time was 0.18 μm/hr. Further, the growth rate of the barrier layer was 0.15 μm/hr.

Subsequently, an electron blocking layer was formed on the light emitting layer. The electron blocking layer was an AlGaN layer (Al: 85%, that is, an Al _0.85 Ga _0.15 N layer) containing no dopant. The electron block layer was formed to a thickness of 20 nm at a temperature of 1080° C., a vacuum degree of 50 mbar, and a V/III ratio of 4000. The growth rate of the electron block layer at this time was 0.35 μm/hr. Further, trimethylaluminum (TMAl) was used as an Al raw material. Further, triethyl gallium (TEGa) was used as a Ga raw material.

Subsequently, a p-type contact layer, which is a second conductivity type contact layer, was formed on the electron block layer. Here, the p-type contact layer was formed of an AlGaN layer and a GaN layer. The AlGaN layer was a p-type nitride semiconductor layer with a thickness of 30 nm, using Mg as a dopant impurity, and having an Al composition distribution in the direction away from the substrate, varying from Al=0.7 to 0.4. Further, the GaN layer was formed of GaN (ie, Al: 0%) having a thickness of 10 nm.
The second conductivity type contact layer was formed at a temperature of 950° C., a vacuum degree of 150 mbar, and a V/III ratio of 3650. The growth rate of the second conductivity type contact layer at this time was 0.2 μm/hr.

Cross-sectional TEM observation and XPS measurement were performed on the nitride semiconductor laminate obtained as described above. As a result, a layer with a different contrast of 20 nm was observed at the boundary between the substrate and the first conductivity type cladding layer from the cross-sectional TEM measurement. XPS measurements showed that the stoichiometric ratio of this layer was more group III atoms than nitrogen. Furthermore, the film thickness was also consistent with the cross-sectional TEM measurement. From the SIMS measurement, 5.0×10 ¹⁸ cm ⁻³ of hydrogen was detected in this layer.

In the manner described above, a semiconductor laminated portion was formed on the AlN substrate. When a reciprocal lattice mapping measurement was performed using XRD on this semiconductor stack, it was found that the semiconductor stack had undergone pseudomorphic growth without relaxation up to the second conductivity type contact layer.
The semiconductor stack formed as described above was annealed at 700° C. for 10 minutes or more in an N ₂ atmosphere to further reduce the resistance of the second conductivity type contact layer. By performing dry etching with a gas containing Cl ₂ using ICP, a mesa structure in which the first conductivity type cladding layer was exposed was formed.

The mesa structure formed was circular with a diameter of 700 μm. Circular Ni and Au films were sequentially formed on the second conductivity type contact layer in the mesa structure to form a p-type second electrode. At this time, the second electrode had a diameter of 500 μm. Further, in the region where the n-type cladding layer of the mesa structure was exposed, V, Al, Ni, Ti, and Au were deposited in order to form an electrode metal region, thereby forming an n-type first electrode. The first electrode and the second electrode were annealed at 550° C. for 60 seconds in a nitrogen atmosphere using an RTA apparatus.
When the light emitting diode obtained in this way was measured for emission intensity by current injection, the threshold voltage was 6.5 V and the emission intensity was 80 mW.

<Comparative example 1>
The laser of Example 2 was produced in the same manner as in Example 1, except that the AlGaN annealing treatment was performed in an environment of 1180° C. and the first conductivity type cladding layer was formed with a thickness of 300 nm on the altered nitride semiconductor layer. formed a diode.
Cross-sectional TEM observation and XPS measurement were performed on the nitride semiconductor laminate obtained as described above. As a result, a layer with a different contrast of 20 nm was observed at the boundary between the substrate and the first conductivity type cladding layer from the cross-sectional TEM measurement. According to XPS measurements, the stoichiometric ratio of this layer was 1:1, and it was not a modified nitride semiconductor layer. Furthermore, no hydrogen was detected in this layer or interface from SIMS measurements.
When the laser diode thus obtained was subjected to current-edge emission intensity measurement by current injection, the threshold voltage was 15 V and the oscillation threshold current was 12.5 kA/cm ² .

<Comparative example 2>
A laser diode of Comparative Example 2 was formed in the same manner as in Example 1 except that the AlGaN annealing treatment was performed in an environment containing only hydrogen.
Cross-sectional TEM observation and XPS measurement were performed on the nitride semiconductor laminate obtained as described above. As a result, a layer with a different contrast of 20 nm was observed at the boundary between the substrate and the first conductivity type cladding layer from the cross-sectional TEM measurement. According to XPS measurements, the stoichiometric ratio of this layer was 1:1, and it was not a modified nitride semiconductor layer. Furthermore, no hydrogen was detected in this layer or interface from SIMS measurements.
When the laser diode thus obtained was subjected to current-edge emission intensity measurement by current injection, the threshold voltage was 12 V and the oscillation threshold current was 8.5 kA/cm ² .

<Comparative example 3>
A laser diode of Comparative Example 3 was formed in the same manner as in Example 1 except that the AlGaN annealing treatment was performed in an environment of nitrogen and NH ₃ .
Cross-sectional TEM observation and XPS measurement were performed on the nitride semiconductor laminate obtained as described above. As a result, a layer with a different contrast of 20 nm was observed at the boundary between the substrate and the first conductivity type cladding layer from the cross-sectional TEM measurement. According to XPS measurements, the stoichiometric ratio of this layer was 1:1, and it was not a modified nitride semiconductor layer. Furthermore, no hydrogen was detected in this layer or interface from SIMS measurements.
When the laser diode thus obtained was subjected to current-edge emission intensity measurement by current injection, the threshold voltage was 12 V and the oscillation threshold current was 8.5 kA/cm ² .

<Comparative example 4>
A laser diode of Comparative Example 4 was formed in the same manner as in Example 1 except that the AlGaN annealing treatment was performed in an environment of 100 mbar.
Cross-sectional TEM observation and XPS measurement were performed on the nitride semiconductor laminate obtained as described above. As a result, a layer with a different contrast of 20 nm was observed at the boundary between the substrate and the first conductivity type cladding layer from the cross-sectional TEM measurement. According to XPS measurements, the stoichiometric ratio of this layer was 1:1, and it was not a modified nitride semiconductor layer. Furthermore, no hydrogen was detected in this layer or interface from SIMS measurements.
When the laser diode thus obtained was subjected to current-edge emission intensity measurement by current injection, the threshold voltage was 12 V and the oscillation threshold current was 8.5 kA/cm ² .

<Comparative example 5>
A GaN layer was formed as a buffer layer on the substrate. The GaN layer was formed to a thickness of 20 nm at a temperature of 1000° C., a vacuum degree of 150 mbar, and a V/III ratio of 4000. The growth rate of the GaN layer at this time was 0.4 μm/hr. Further, triethyl gallium (TEGa) was used as a Ga raw material. Furthermore, ammonia (NH ₃ ) was used as the N raw material. A laser diode of Comparative Example 5 was formed in the same manner as in Example 1 except for the above.

Cross-sectional TEM observation and XPS measurement were performed on the nitride semiconductor laminate obtained as described above. As a result, a layer with a different contrast of 20 nm was observed at the boundary between the substrate and the first conductivity type cladding layer from the cross-sectional TEM measurement. According to XPS measurements, the stoichiometric ratio of this layer was 1:1, and it was not a modified nitride semiconductor layer. Furthermore, no hydrogen was detected in this layer or interface from SIMS measurements.
When the laser diode thus obtained was subjected to current-edge emission intensity measurement by current injection, the threshold voltage was 12 V and the oscillation threshold current was 8.5 kA/cm ² .

Table 1 below shows the evaluation results of each Example and each Comparative Example.

As shown in Table 1, the stoichiometric ratio of group III atoms and group V atoms is not 1:1 between the nitride semiconductor substrate and the first conductivity type cladding layer, or hydrogen is present at 1×10 ¹⁸ The laser diode (light-emitting element) of each example including a modified nitride semiconductor layer containing 5×10 cm ^{-3 or} more and 5×10 ¹⁹ cm -3 or less is different from the laser diode (light-emitting element) of each comparative example that does not include the modified nitride semiconductor layer. ), the threshold voltage and oscillation threshold were significantly lower. In addition, the stoichiometric ratio of group III atoms and group V atoms between the nitride semiconductor substrate and the first conductivity type cladding layer is not 1:1, or hydrogen is present at 1×10 ¹⁸ cm ⁻³ or more 5 Similarly, the light emitting diode (light emitting element) of Example 10 including the modified nitride semiconductor layer containing 10 ¹⁹ cm ^-3 or less had a low threshold voltage and high emission intensity.
In such a light-emitting element, the buffer layer is a nitride buffer layer containing Al, the annealing temperature is 1200°C or more and less than 1400°C, and the degree of vacuum is 10 mbar when forming the modified nitride semiconductor layer. 50 mbar or less, and it was found that this can be obtained by manufacturing a modified nitride semiconductor layer by exposing the layer alternately to hydrogen and NH ₃ during heat treatment.

Further, from Examples 1 to 5, by setting the annealing temperature at the time of manufacturing the modified nitride semiconductor layer to 1200°C or more and 1350°C or less, the thickness of the modified nitride semiconductor layer becomes 3 nm or more and 40 nm or less, and the oscillation threshold is further improved. It was found that this reduction was favorable.

The embodiments of the present disclosure have been described above, but the embodiments described above illustrate devices and methods for embodying the technical idea of the present disclosure, and the technical idea of the present disclosure It does not specify the material, shape, structure, arrangement, etc. The technical idea of the present disclosure can be modified in various ways within the technical scope defined by the claims.

1 Laser diode 2 Light emitting diode 10 Semiconductor stack 11 Substrate 12 First electrode 13 Second electrode 20 Semiconductor stack 101 Altered nitride semiconductor layer 102 First conductivity type cladding layer 103 First waveguide layer 104 Light emitting layer 105 2 waveguide layer 106 second conductivity type cladding layer 107 contact layer 201 altered nitride semiconductor layer 202 first conductivity type cladding layer 203 light emitting layer 204 electron block layer 205 second conductivity type cladding layer 206 contact layer

Claims (14)

A nitride buffer layer containing Al is formed on a nitride semiconductor substrate containing Al, and the nitride buffer layer is heated in hydrogen and NH ₃ in an environment where the reactor pressure is 10 mbar or more and 50 mbar or less and 1200° C. or more and 1400° C. or less. forming a modified nitride semiconductor layer by alternately performing heat treatment in the modified nitride semiconductor layer; forming a first conductivity type cladding layer including a first conductivity type nitride semiconductor layer on the modified nitride semiconductor layer; A light emitting layer made of a nitride semiconductor including one or more quantum wells is formed on the first conductivity type cladding layer, and a second conductivity type cladding layer including a second conductivity type nitride semiconductor layer is formed on the light emitting layer. A method for manufacturing a light emitting device, which comprises forming a cladding layer to form a semiconductor laminated portion. 2. The method for manufacturing a light emitting device according to claim 1, wherein the modified nitride semiconductor layer is formed in which the stoichiometric ratio of group III atoms to group V atoms is not 1:1. 3. The method for manufacturing a light emitting device according to claim 1, wherein the modified nitride semiconductor layer containing hydrogen in an amount of 1×10 ¹⁸ cm ⁻³ or more and 5×10 ¹⁹ cm ^{−3 or} less is formed. a nitride semiconductor substrate containing Al;
a semiconductor stacked section disposed on the nitride semiconductor substrate;
Equipped with
The semiconductor laminated portion includes:
a first conductivity type cladding layer disposed on the nitride semiconductor substrate and including a first conductivity type nitride semiconductor layer;
a light-emitting layer disposed on the first conductivity type cladding layer and formed of a nitride semiconductor including one or more quantum wells;
a second conductivity type cladding layer disposed on the light emitting layer and including a second conductivity type nitride semiconductor layer;
has
The light emitting device includes a modified nitride semiconductor layer in which the stoichiometric ratio of group III atoms and group V atoms is not 1:1 between the nitride semiconductor substrate and the first conductivity type cladding layer. 5. The light emitting device according to claim 4, wherein the altered nitride semiconductor layer contains hydrogen in an amount of 1×10 ¹⁸ cm ⁻³ or more and 5×10 ¹⁹ cm ^{−3 or} less. a nitride semiconductor substrate containing Al;
a semiconductor stacked section disposed on the nitride semiconductor substrate;
Equipped with
The semiconductor laminated portion includes:
a first conductivity type cladding layer disposed on the nitride semiconductor substrate and including a first conductivity type nitride semiconductor layer;
a light-emitting layer disposed on the first conductivity type cladding layer and formed of a nitride semiconductor including one or more quantum wells;
a second conductivity type cladding layer disposed on the light emitting layer and including a second conductivity type nitride semiconductor layer;
has
A light emitting device comprising a modified nitride semiconductor layer containing hydrogen in an amount of 1×10 ¹⁸ cm ⁻³ or more and 5×10 ¹⁹ cm ^{−3 or} less between the nitride semiconductor substrate and the first conductivity type cladding layer. 6. The light emitting device according to claim 4, wherein the number of nitrogen atoms contained in the modified nitride semiconductor layer is smaller than the total number of group III atoms. The light emitting device according to any one of claims 4 to 7, wherein the modified nitride semiconductor layer has a thickness of 3 nm or more and 40 nm or less. 9. The light emitting device according to claim 4, wherein the modified nitride semiconductor layer is made of AlGaN. The light emitting device according to any one of claims 4 to 9, wherein the nitride semiconductor substrate is an AlN single crystal substrate. The first conductivity type cladding layer is formed of Al _a Ga _1-a N (0.65<a≦0.90).
The light emitting device according to any one of claims 4 to 10. The thickness of the first conductivity type cladding layer is 250 nm or more and 800 nm or less,
The light emitting device according to any one of claims 4 to 11. a first waveguide layer disposed between the first conductivity type cladding layer and the light emitting layer to confine light to the light emitting layer;
a second waveguide layer disposed between the second conductivity type cladding layer and the light emitting layer to confine light to the light emitting layer;
The light emitting device according to any one of claims 4 to 12. a second conductivity type contact layer disposed on the second conductivity type cladding layer and formed of a nitride semiconductor containing GaN;
The second conductivity type cladding layer includes Al _b Ga _1-b N (0.1≦b≦1), has a composition gradient in which the Al composition b decreases as it moves away from the nitride semiconductor substrate, and has a film thickness. is less than 0.5 μm, and a second conductivity type horizontal conduction layer containing Al _c Ga _1-c N (0<c≦1),
The light emitting device according to any one of claims 4 to 13.

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