Method for manufacturing nitride semiconductor devices, nitride semiconductor laminates, and method for manufacturing nitride semiconductor devices

Abstract

The present invention provides a nitride semiconductor element which achieves both suppression of deterioration of a cladding layer and improvement of carrier injection efficiency. This nitride semiconductor element comprises: a nitride semiconductor substrate containing Al; and a semiconductor multilayer part that is disposed on the nitride semiconductor substrate. The semiconductor multilayer part comprises: a first conductivity type cladding layer that contains a nitride semiconductor of a first conductivity type; a light emitting layer that is disposed on the first conductivity type cladding layer and is formed of a nitride semiconductor comprising one or more quantum wells; and a second conductivity type cladding layer that is disposed on the light emitting layer and is formed of a nitride semiconductor of a second conductivity type containing Al. In a region of the second conductivity type cladding layer that is between 1 nm and 110 nm inclusive from the nitride semiconductor substrate side thereof, hydrogen is contained at a higher concentration than in the other regions of the second conductivity type cladding layer.

Description

[Technical Field]

[0001] This disclosure relates to a nitride semiconductor device, a method for manufacturing a nitride semiconductor laminate, and a method for manufacturing a nitride semiconductor device. [Background technology]

[0002] Conventionally, nitride semiconductors have been used as materials for forming light-emitting diodes (LEDs) and laser diodes (LDs). Nitride semiconductors are suitable as materials for LEDs and LDs because they have a direct transition recombination mode, which allows for high recombination efficiency and high optical gain. As an example of a laser diode using such a nitride semiconductor, a technique for oscillating a current-injection type laser diode in the ultraviolet region has been disclosed (for example, Non-Patent Document 1). [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Zhang et al., Applied Physics Express 12, 124003(2019) [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] While nitride semiconductor devices such as the laser diodes mentioned above can improve the efficiency of carrier (electron or hole) injection, they do not adequately suppress the degradation of the cladding layer. The purpose of this disclosure is to provide a nitride semiconductor device, a method for manufacturing a nitride semiconductor laminate, and a method for manufacturing a nitride semiconductor device that can achieve both suppression of cladding layer degradation and improvement of carrier injection efficiency. [Means for solving the problem]

[0005] To solve the above-mentioned problems, a nitride semiconductor device according to one aspect of the present disclosure comprises a nitride semiconductor substrate containing Al and a semiconductor laminate disposed on the nitride semiconductor substrate. The semiconductor laminate includes a first conductivity type cladding layer containing a first conductivity type nitride semiconductor, an emissive layer disposed on the first conductivity type cladding layer and formed of a nitride semiconductor containing one or more quantum wells, and a second conductivity type cladding layer disposed on the emissive layer and formed of a nitride semiconductor containing a second conductivity type Al. The region of the second conductivity type cladding layer from the nitride semiconductor substrate side, from 1 nm to 110 nm, contains hydrogen at a higher concentration than other regions of the second conductivity type cladding layer.

[0006] Furthermore, a method for manufacturing a nitride semiconductor laminate according to another aspect of the present disclosure involves forming a first conductivity type cladding layer containing a first conductivity type nitride semiconductor on an Al-containing nitride semiconductor substrate, forming an emissive layer on the first conductivity type cladding layer using a nitride semiconductor containing one or more quantum wells, forming a portion of a second conductivity type cladding layer containing a second conductivity type nitride semiconductor under conditions where the wafer temperature is 900°C or more and 1000°C or less and the reactor pressure is 15 mbar or more and 350 mbar or less, and forming the remaining portion of the second conductivity type cladding layer under conditions where the wafer temperature is 1030°C or more and 1100°C or less and the reactor pressure is 15 mbar or more and 350 mbar or less, thereby forming a semiconductor laminate on the nitride semiconductor substrate.

[0007] Furthermore, in a method for manufacturing a nitride semiconductor device according to another aspect of the present disclosure, after forming a semiconductor laminate by the above-described method for manufacturing a nitride semiconductor laminate, unnecessary portions of each layer of the semiconductor laminate are removed by etching, electrodes are formed on the semiconductor laminate, and the nitride semiconductor substrate on which each layer of the semiconductor laminate is formed is divided into individual pieces by dicing. It should be noted that the above-described summary of the invention does not enumerate all of the features of the invention described herein. [Effects of the Invention]

[0008] According to this disclosure, it is possible to provide a nitride semiconductor device that can achieve both suppression of cladding layer degradation and improvement of carrier injection efficiency, a method for manufacturing a nitride semiconductor laminate, and a method for manufacturing a nitride semiconductor device. [Brief explanation of the drawing]

[0009] [Figure 1] This graph shows one example of the Al composition in a nitride semiconductor device according to the embodiment of this disclosure. [Figure 2A] This is an AFM photograph showing the structure of the upper surface of the second conductivity type cladding layer of a nitride semiconductor device according to an embodiment of this disclosure. [Figure 2B] This is an SEM image showing the structure of the upper surface of the second conductivity type cladding layer of a nitride semiconductor device according to an embodiment of this disclosure. [Figure 3] This is an AFM photograph showing the structure of the upper surface of the second conductivity type cladding layer of a conventional nitride semiconductor device. [Figure 4] This is a schematic cross-sectional view showing one example of the configuration of a nitride semiconductor device according to the present disclosure. [Figure 5] This is a schematic cross-sectional view showing one example of the configuration of a nitride semiconductor device according to the present disclosure. [Figure 6] This is a schematic cross-sectional view showing one example of the configuration of a nitride semiconductor device according to the present disclosure. [Figure 7] This is a schematic cross-sectional view showing one example of the configuration of a nitride semiconductor device according to the present disclosure. [Modes for carrying out the invention]

[0010] The nitride semiconductor elements relating to this disclosure will be described below through embodiments, but the following embodiments are not intended to limit the invention as claimed. Furthermore, not all combinations of features described in the embodiments are necessarily essential to the solution of the invention. Furthermore, in the following explanation, "up" and "down" do not necessarily mean the vertical direction relative to the ground. In other words, the directions of "up" and "down" are not limited to the direction of gravity. "Up" and "down" are merely convenient expressions to specify the relative positional relationship on a surface, film, substrate, etc., and do not limit the technical concept of the present invention. For example, it goes without saying that if the paper is rotated 180 degrees, "up" becomes "down" and "down" becomes "up".

[0011] 1. First Embodiment A nitride semiconductor device according to the first embodiment of this disclosure will be described. The nitride semiconductor device according to this embodiment is, for example, a laser diode. The following describes the case where the nitride semiconductor element is a laser diode.

[0012] (1.1) Laser Diode Configuration The laser diode according to this embodiment comprises an Al-containing nitride semiconductor substrate and a semiconductor laminate disposed on the nitride semiconductor substrate. The semiconductor laminate includes a first conductivity type cladding layer containing a first conductivity type nitride semiconductor, an emissive layer disposed on the first conductivity type cladding layer and formed of a nitride semiconductor containing one or more quantum wells, and a second conductivity type cladding layer disposed on the emissive layer and formed of a second conductivity type Al-containing nitride semiconductor. The region of the second conductivity type cladding layer from the nitride semiconductor substrate side, from 1 nm to 110 nm, contains hydrogen at a higher concentration than other regions of the second conductivity type cladding layer. The following provides a detailed explanation of each layer of the laser diode.

[0013] <Nitride semiconductor substrates> The nitride semiconductor substrate (hereinafter sometimes referred to as "substrate") contains an Al-containing nitride semiconductor. The Al-containing nitride semiconductor is, for example, AlN. That is, the substrate is preferably an AlN single crystal substrate. Furthermore, the Al-containing nitride semiconductor is not limited to AlN, and may be, for example, AlGaN. For example, when the substrate is an AlN, AlGaN, or other nitride semiconductor single crystal substrate, the lattice constant difference with the nitride semiconductor layer formed on the upper side of the substrate becomes small, and the number of threading dislocations can be reduced by growing the nitride semiconductor layer in a lattice-matched system. The through-dislocation density of the substrate is 5 × 10⁻⁶ 4 cm -2 The following is preferable. In particular, from the viewpoint of improving luminescence intensity and reducing oscillation threshold current, the through-dislocation density is 1 × 10⁻⁶. 3 cm -2 The above 1 x 10 4 cm -2 The following is more preferable: Furthermore, the substrate may be formed on a different type of substrate, as long as it contains a nitride semiconductor containing Al. For example, AlN may be grown on a sapphire (Al2O3) substrate.

[0014] Here, the phrase "contains nitride semiconductors" means that nitride semiconductors are primarily contained within the layer, but it also includes cases where other elements are present. Specifically, this expression includes cases where minor changes are made to the composition of this layer, such as adding small amounts of elements other than nitride semiconductors (for example, a few percent or less of elements such as Ga (if Ga is not the main element), In, As, P, or Sb). The word "contains" has the same meaning when describing the composition of other layers. Furthermore, the above does not apply to the small amounts of elements that may be included.

[0015] The substrate preferably has a layer thickness of 100 μm to 600 μm, for example. The plane orientation can be c-plane (0001), a-plane (11-20), m-plane (10-10), etc., but a c-plane (0001) substrate is more preferred. Furthermore, it can be formed on a plane inclined at some angle (e.g., -4° to 4°, preferably -0.4° to 0.4°) from the c-plane (0001) normal direction, but is not limited to this.

[0016] <buffer layer> A buffer layer may be formed on the substrate, that is, between the substrate and the first conductivity type cladding layer. Preferably, the buffer layer is formed over the entire surface of the substrate. By providing a buffer layer, a nitride semiconductor layer with small lattice constant differences and thermal expansion coefficient differences and few defects is formed on the buffer layer. The buffer layer is preferably an Al-containing nitride semiconductor layer, and is formed from a nitride semiconductor such as AlN or AlGaN. The buffer layer may also contain impurities such as C, Si, Fe, and Mg.

[0017] The buffer layer has a thickness of, for example, several micrometers. Specifically, the buffer layer is preferably thicker than 10 nm and thinner than 10 μm. When the buffer layer is thicker than 10 nm, the crystallinity of nitride semiconductors such as AlN increases. Also, when the buffer layer is thinner than 10 μm, cracks are less likely to occur in the buffer layer formed by crystal growth across the entire wafer surface.

[0018] <First conductive cladding layer> The first-conductivity-type clad layer is formed on the substrate. Here, for example, in the expression "The first-conductivity-type clad layer is formed on the substrate", the phrase "on" means that the first-conductivity-type clad layer is formed on one surface of the substrate. Also, the above expression includes the case where there is another layer further between the substrate and the first-conductivity-type clad layer. In the relationship between other layers as well, the phrase "above" has the same meaning. For example, when the second-conductivity-type clad layer is formed via an electron blocking layer on the first-conductivity-type waveguide layer described later, it is also included in the expression "The second-conductivity-type clad layer is formed on the first-conductivity-type waveguide layer". Also, in the description of this embodiment, "the first conductivity type" and "the second conductivity type" each mean a semiconductor indicating a different conductivity type. For example, when one is n-type conductivity, the other is p-type conductivity.

[0019] The first-conductivity-type clad layer is a layer of a nitride semiconductor containing Al and Ga. The first-conductivity-type clad layer is, for example, Al a Ga (1-a) formed by N (0 < a < 1). Thereby, when forming a material corresponding to the bandgap energy in the deep ultraviolet region as a light-emitting layer, it becomes possible to enhance the crystallinity of the light-emitting layer and improve the light-emitting efficiency. From the viewpoint of realizing high light-emitting efficiency, the nitride semiconductor constituting the first-conductivity-type clad layer is preferably a mixed crystal of AlN and GaN. Also, from the viewpoint of growing the first-conductivity-type clad layer and each layer formed in the upper layer with complete strain with respect to the substrate, the first-conductivity-type clad layer is Al a Ga (1-a) more preferably formed by N (0.65 < a ≦ 0.9).

[0020] The first-conductivity-type clad layer may be a gradient layer in which the Al composition increases as it moves away from the substrate for the purpose of controlling the longitudinal conductivity. In this case, the above limitation on the Al composition can be the Al composition averaged by the film thickness of the first-conductivity-type clad layer for the Al composition at the position in the film thickness direction within the first-conductivity-type clad layer. When the first conductive type clad layer is an n-type conductive semiconductor layer, it may contain impurities such as group V elements other than N such as P, As, Sb, and impurities such as C, H, F, O, Mg, Si, etc., but the types of impurity elements are not limited to this. From the viewpoint of reducing electrical resistance and the availability of raw materials, the impurity contained in the first conductive type clad layer is preferably Si, and the impurity concentration is 5×10 18 cm -3 or more and 5×10 19 cm -3 below is preferable. Also, the resistivity of the first conductive type clad layer is preferably 1×10 -3 Ω · cm or more and 5×10 -3 Ω · cm or less. Thereby, carrier injection can be efficiently performed.

[0021] The first conductive type clad layer preferably has a layer thickness of 250 nm or more and 800 nm or less, and more preferably has a layer thickness of 300 nm or more and 450 nm or less, from the viewpoints of lattice relaxation within the first conductive type clad layer and film resistance.

[0022] <Light-emitting layer> The light-emitting layer is a layer of a nitride semiconductor containing Al and Ga. The nitride semiconductor contained in the light-emitting layer is preferably a mixed crystal of, for example, AlN and GaN from the viewpoint of realizing high luminous efficiency. For example, it is formed by Al b Ga (1-b) N (0 < b < 1). The light-emitting layer may contain impurities such as group V elements other than N such as P, As, Sb, and impurities such as C, H, F, O, Mg, Si, etc., but the types of impurity elements are not limited to this.

[0023] Also, the light-emitting layer can have either a multiple quantum well structure or a single quantum well structure. Although it depends on the longitudinal conductivity of the first conductive type clad layer and the second conductive type clad layer, the number of quantum well structures is preferably any one of 1 to 5.

[0024] In the laser diode of this embodiment, it is preferable that α, which indirectly represents the potential fluctuation of the nitride semiconductor layer, is between 130 meV and 350 meV. The nitride semiconductor layer represented by such α may be not only the light-emitting layer, but also the first conductivity type waveguide layer or the second conductivity type waveguide layer described later. When α of the light-emitting layer, the first conductivity type waveguide layer, or the second conductivity type waveguide layer is between 130 meV and 350 meV, recombination of localized carriers occurs efficiently, and the light emission efficiency can be improved. Here, "potential fluctuation of the nitride semiconductor layer" is an index for identifying the distribution state of Ga in the plane direction of the nitride semiconductor layer, and "α, which indirectly represents the potential fluctuation," is an index that shows the deviation from the uniformity of the alloy in the plane direction of the nitride semiconductor layer. When the above-mentioned α is 30 meV (approximately), it indicates that Ga is uniformly distributed in the plane direction of the nitride semiconductor layer, that is, Al and Ga are uniformly aligned. Such potential fluctuations manifest in the full width at half maximum (FWHM) of the emission spectrum of the nitride semiconductor layer. That is, the closer the nitride semiconductor constituting the nitride semiconductor layer is to a perfectly uniform crystal, the narrower the FWHM of the emission spectrum becomes. On the other hand, the possible values ​​of the FWHM of the emission spectrum also differ depending on the Al composition of the nitride semiconductor. Therefore, we evaluate the potential fluctuations of the nitride semiconductor layer using α, which represents the deviation from the FWHM of the emission spectrum in a uniform state for each Al composition. The Al composition x of the nitride semiconductor layer and the FWHM of the emission spectrum at the emission wavelength can be expressed by the equation FWHM(meV) = αx + 10meV. In this case, if α is large, it can be said that it is far from a uniform state, that is, Ga and other elements are segregated or localized.

[0025] Furthermore, the thickness of the region where the Al concentration profile changes in a gradient at the interface between the well layer and the barrier layer in the light-emitting layer is preferably 0.3 nm or more and 0.6 nm or less. This allows for improved carrier confinement and increased luminescence intensity.

[0026] Waveguide layer From the perspective of optical confinement as a laser diode, the laser diode of the present embodiment may be provided with a waveguide layer that 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 is preferably composed of two layers, namely, a first-conductivity-type waveguide layer disposed between the first-conductivity-type clad layer and the light-emitting layer, and a second-conductivity-type waveguide layer disposed between the second-conductivity-type clad layer and the light-emitting layer. That is, the laser diode of the present embodiment may include, for example, a first-conductivity-type waveguide layer disposed between the first-conductivity-type clad layer and the light-emitting layer and confining light to the light-emitting layer, and a second-conductivity-type waveguide layer disposed between the second-conductivity-type clad layer and the light-emitting layer and confining light to the light-emitting layer.

[0027] From the perspective of optical confinement, the waveguide layer is preferably a nitride semiconductor containing Al and Ga having a bandgap higher in energy than the light-emitting layer. The waveguide layer preferably has an Al composition and a film thickness that increase the overlap between the electric field strength distribution of the light standing in the device and the light-emitting layer. From the perspective of carrier confinement in the light-emitting layer, the light-emitting layer is Al mode Ga b Ga (1-b) N (0 < b < 1), and when the waveguide layer is Al c Ga (1-c) N (0 < c < 1), it is more preferable that b < c and c ≧ b + 0.05. For example, when the light-emitting layer having an emission wavelength of 265 nm is taken as an example, b is 0.52, and c is preferably 0.57 or more. Also, from the perspectives of optical confinement and sheet resistance, the total film thickness of the waveguide layer (the total film thickness of the first-conductivity-type waveguide layer and the second-conductivity-type waveguide layer) is preferably 70 nm or more and 150 nm or less.

[0028] The waveguide 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 the types of impurity elements are not limited to this. From the perspective of reducing electrical resistance and the ease of obtaining raw materials, the impurity contained in the first-conductivity-type waveguide layer is preferably Si, and the impurity concentration is 5 × 1018 cm -3 The above 5 x 10 19 cm -3 below It is preferable that this be the case.

[0029] The Al composition of the first conductivity type waveguide layer and the second conductivity type waveguide layer is preferably uniform in the film thickness direction, but is not limited to this. In order to avoid light absorption by the metal (e.g., the second electrode) located above the second conductivity type cladding layer, which will be described later, the Al composition of the second conductivity type waveguide layer may be higher than that of the first conductivity type waveguide layer. For the same purpose, the film thickness of the second conductivity type waveguide layer may be the same as that of the first conductivity type waveguide layer. Conductive type Waveguide layer It may be thicker than the film thickness.

[0030] <Second conductive 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 having second conductivity type properties. The second conductivity type cladding layer is, for example, Al d Ga (1-d) It is formed by N(0.1≦d≦1). Specifically, the second conductivity type cladding layer is formed on the second conductivity type waveguide layer. This allows for easy lattice matching of the second conductivity type cladding layer with respect to the light-emitting layer or waveguide layer, and enables suppression of the penetration dislocation density.

[0031] The second conductivity type cladding layer is not particularly limited as long as it has sufficient conductivity to inject carriers (electrons or holes) into the light-emitting layer and can increase the overlap between the electric field intensity distribution of resident optical modes in the device and the light-emitting layer (i.e., increase optical confinement). The second conductivity type cladding layer may be, for example, Mg-doped p-type AlGaN. Furthermore, the second conductivity type cladding layer may contain impurities such as group V elements other than N, such as P, As, and Sb, as well as C, H, F, O, Mg, and Si, but the types of impurities are not limited to these.

[0032] From the viewpoint of more efficiently injecting carriers into the light-emitting layer, the second conductive cladding layer has a compositional gradient such that the Al composition d decreases as the layer moves away from the substrate. d Ga (1-d) The layers are formed with a compositional gradient of N (0.1 ≤ d ≤ 1), but in a portion of the second conductive cladding layer, the Al composition d increases as it moves away from the substrate. The second conductivity type cladding layer preferably has a composition gradient in which the Al composition d decreases in the range of 1 to 0.7 as it moves away from the nitride semiconductor substrate. The profile (gradient) of the Al composition d in the second conductivity type cladding layer may decrease continuously or intermittently. Here, "intermittently decreases" means that a portion of the film of the second conductivity type cladding layer contains a part in which the Al composition d is the same (constant in the film thickness direction). In other words, the second conductivity type cladding layer may contain a portion in which the Al composition d does not decrease in the direction away from the substrate (a portion in which the Al composition d is constant or increases).

[0033] The thickness of the second conductive cladding layer is preferably 500 nm or less from the viewpoint of lattice matching. Furthermore, from the viewpoint of light confinement, it is more preferably between 250 nm and 500 nm.

[0034] Figure 1 shows the Al composition (shown by thick lines) and impurity composition (shown by solid lines) in each layer of the laser diode. Note that Figure 1 shows an example of a structure without a buffer layer. As shown in Figure 1, the second conductivity cladding layer has a compositional gradient such that the Al composition d decreases as it moves away from the substrate. Some regions of the second conductivity cladding layer are doped with impurities such as carbon or oxygen. These impurities are also doped, for example, in the interface gradient portion on the second conductivity waveguide layer where the Al composition increases, and the concentration profile increases discontinuously at the starting point of the composition gradient layer (the interface on the second conductivity waveguide layer side). Conventionally, the second conductivity type cladding layer is often formed from nitride semiconductors with little or no impurities, in order to suppress the diffusion of impurities and improve injection efficiency. However, by including a large amount of impurities in a portion of the second conductivity type cladding layer, it is possible to achieve both suppression of degradation and improvement of injection efficiency in the second conductivity type cladding layer.

[0035] Furthermore, it is preferable that the second conductivity type cladding layer has a region in which the concentration profile of carbon or oxygen contained in the second conductivity type cladding layer changes discontinuously at least at one point as it moves away from the substrate. That is, it is preferable that the impurity concentration profile has a region that is convex in the direction of increasing concentration. By having such a discontinuous region, the second conductivity type cladding layer has a part of the second conductivity type cladding layer that exhibits a degradation suppression effect and the remaining part of the second conductivity type cladding layer that exhibits an improvement in the carrier (electron or hole) injection efficiency into the light-emitting layer. In this case, the carbon or oxygen concentration profile in the second conductivity type cladding layer slopes steeply, improving the carrier injection efficiency into the light-emitting layer, and the second conductivity type cladding layer can achieve both the degradation suppression effect and the improvement in carrier injection efficiency into the light-emitting layer. Generally, if the impurity concentration profile has a region that is convex in the direction of increasing concentration, it is disadvantageous in terms of carrier injection efficiency into the light-emitting layer, but the second Conductive type Depending on the thickness of the cladding layer, creating regions where the carbon or oxygen concentration profile slopes steeply can be advantageous in terms of overall carrier injection efficiency into the emissive layer.

[0036] Here, "a region where the concentration profile discontinuously decreases as you move away from the substrate (nitride semiconductor substrate) at least at one point" refers to a region where the impurity concentration in a given region (the impurity concentration measured at a measurement point within that region) differs from the surrounding impurity concentration (the impurity concentration measured at a measurement point in an adjacent region) by more than twice the amount. For example, as shown in Figure 1, there is a region P where the impurity concentration profile changes abruptly.

[0037] As described above, the second conductivity type cladding layer has a region P in which the impurity concentration profile decreases discontinuously. The region P in which the concentration profile decreases discontinuously is preferably located in a region of 1 nm to 110 nm from the substrate side of the second conductivity type cladding layer, and more preferably in a region of 5 nm to 110 nm. This makes it possible to suppress the degradation of the second conductivity type cladding layer without hindering the improvement of the carrier injection efficiency into the light-emitting layer.

[0038] Furthermore, in the second conductive cladding layer, the region closer to the substrate than region P where the impurity concentration profile decreases discontinuously is Al e Ga (1-e) It is preferable that the layer is formed with N(0.8≦e≦1.0). This makes it possible to suppress the degradation of the second conductive cladding layer without hindering the improvement of the carrier injection efficiency into the light-emitting layer. In the second conductive cladding layer, the carbon concentration in the region closer to the substrate than region P where the impurity concentration profile decreases discontinuously is 1 × 10⁻⁶ 17 cm -3 The above 1 x 10 18 cm -3 The following is preferable. Similarly, in the second conductive cladding layer, the oxygen concentration in the region on the substrate side of region P where the impurity concentration profile decreases discontinuously is 1 × 10 17 cm -3 The above 1 x 10 18 cm -3 The following is preferable. This allows for the formation of a layer that effectively suppresses the degradation of the second conductivity type cladding layer and a layer that effectively improves the carrier injection efficiency into the light-emitting layer. Therefore, it is possible to better achieve both the effect of suppressing the degradation of the second conductivity type cladding layer and the effect of improving the carrier injection efficiency into the light-emitting layer in the laser diode.

[0039] As described above, the second conductive cladding layer in the embodiment shown in Figure 1 is Al d Ga (1-d)The second conductivity type cladding layer contains N (0.1 ≤ d ≤ 1) and has a compositional gradient in which the Al composition d decreases as it moves away from the nitride semiconductor substrate. Furthermore, at least a portion of the second conductivity type cladding layer is a compositional discontinuity region Q in which the Al composition is discontinuous in the direction away from the substrate, and in the compositional discontinuity region Q, the Al composition d increases as it moves away from the substrate. In this way, by having a compositional discontinuity region Q in the second conductivity type cladding layer, the laser diode can achieve both the effect of suppressing the degradation of the second conductivity type cladding layer and the effect of improving the carrier injection efficiency into the light-emitting layer.

[0040] The compositional discontinuity region Q is preferably located in a region of 1 nm to 110 nm from the nitride semiconductor substrate side of the second conductivity type cladding layer, and more preferably in a region of 5 nm to 110 nm. That is, the starting point of the compositional discontinuity region Q preferably coincides with the starting point of region P. By having the compositional discontinuity region Q on the nitride semiconductor substrate side of the second conductivity type cladding layer, degradation of the second conductivity type cladding layer can be suppressed without hindering the improvement of the carrier injection efficiency into the light-emitting layer. Furthermore, it is preferable that the compositional discontinuity region Q has a compositional gradient in which the Al composition d increases by 0.002 or more and 0.05 or less as it moves away from the substrate. Having such a compositional gradient in the compositional discontinuity region Q allows for the formation of a layer that effectively suppresses the degradation of the second conductivity type cladding layer and a layer that effectively improves the carrier injection efficiency into the light-emitting layer. Therefore, it is possible to better achieve both the degradation suppression effect of the second conductivity type cladding layer and the improvement of carrier injection efficiency into the light-emitting layer in the laser diode.

[0041] Furthermore, at the substrate-side interface of the second conductive cladding layer (i.e., the interface with the second conductive waveguide layer), hydrogen is present in a quantity of 1 × 10⁻¹⁶. 17 cm -3 The above 5 x 10 19 cm -3The following are preferably included: It is preferable that at least a portion of the second conductivity type cladding layer contains hydrogen at a higher concentration than other portions of the second conductivity type cladding layer. Although the second conductivity type cladding layer as a whole contains trace amounts of hydrogen, the second conductivity type cladding layer of the laser diode of this embodiment includes a portion of the layer containing hydrogen at a high concentration. This allows the laser diode to compensate for point defects and achieve both the effect of suppressing degradation of the second conductivity type cladding layer and the effect of improving the carrier injection efficiency into the light-emitting layer.

[0042] The region containing hydrogen at a higher concentration than other regions of the second conductivity cladding layer is preferably a region of 1 nm to 110 nm from the substrate side of the second conductivity cladding layer, and more preferably a region of 5 nm to 110 nm. This allows for compensation of point defects and suppression of degradation of the second conductivity cladding layer without hindering the improvement of carrier injection efficiency into the light-emitting layer. Furthermore, the half-width of the hydrogen concentration profile in regions of the second conductive cladding layer that contain hydrogen at a higher concentration than other regions is preferably between 5 nm and 10 nm. This effectively compensates for point defects and improves the carrier injection efficiency into the light-emitting layer.

[0043] Furthermore, at the substrate-side interface of the second conductive cladding layer, silicon is present in a quantity of 1 × 10⁻⁶. 17 cm -3 The above 5 x 10 19 cm -3 The following may also be included: At least a portion of the second conductivity cladding layer may contain silicon at a higher concentration than other areas of the second conductivity cladding layer. The area containing silicon at a higher concentration than other areas of the second conductivity cladding layer is preferably an area of ​​1 nm to 110 nm from the substrate side of the second conductivity cladding layer, and more preferably an area of ​​5 nm to 110 nm.

[0044] As shown in Figure 2A, the surface of the second conductivity type cladding layer described above has a spiral step terrace structure with terraces and steps that are not linear in a plan view. One example of a spiral step terrace structure is a shape based on a hexagon in which one side of the outline gradually shortens. Other examples of spiral step terrace structures are a shape based on a circle in which its radius gradually shortens, or a shape based on a mixed shape of a hexagon and a line in which the length of the sides gradually shortens. For comparison, Figure 3 shows a step terrace structure with linear terraces and steps in a plan view. This makes it possible to better achieve both the effect of suppressing the degradation of the second conductivity type cladding layer in the laser diode and the effect of improving the carrier injection efficiency into the light-emitting layer. Such a second-conductivity cladding layer can be formed by growing it at a lower temperature than conventional methods (which will be explained in detail later), resulting in a transition from a linear step terrace structure to a spiral step terrace structure. Here, Figure 2A is an atomic force microscope (AFM) image showing the spiral step terrace structure, and Figure 2B is a scanning electron microscope (SEM) image showing the circular step terrace structure. Compared to cases where a circular or linear step terrace structure is formed on the surface of the second-conductivity cladding layer, a higher improvement in the luminescence efficiency of the second-conductivity cladding layer can be obtained when a spiral step terrace structure is formed. This is thought to be because Ga segregates during the growth process of the spiral step terrace film, improving the current injection efficiency.

[0045] The height of the spiral step terrace structure is preferably between 0.2 nm and 0.4 nm. Furthermore, the distribution density of the spiral step terrace structure is 1 × 10⁻⁶. 7 cm -2 The above 5 x 10 8 cm -2 The following is preferable: This results in an even higher degradation suppression effect for the second conductivity type cladding layer and an improvement in current injection efficiency.

[0046] Furthermore, if a nitride semiconductor layer having a spiral-shaped step terrace structure is formed, and then a nitride semiconductor layer is deposited using a conventional method to form a second conductivity type cladding layer, the spiral-shaped step terrace structure will also appear on the surface of the second conductivity type cladding layer. Therefore, by observing the surface shape of the second conductivity type cladding layer, the spiral-shaped step terrace structure on the surface of the second conductivity type cladding layer can be confirmed. Also, if a second conductivity type contact layer, as described later, is formed on the second conductivity type cladding layer, the spiral-shaped step terrace structure will no longer appear on the surface of the second conductivity type contact layer. However, if only the second conductivity type contact layer is removed using, for example, sulfur hexafluoride (SF6) gas, the second conductivity type Clad By exposing the layer and observing it using an SEM or similar method, the spiral-shaped step terrace structure on the surface of the second conductive cladding layer can be confirmed.

[0047] <Interface slope> The laser diode according to this embodiment has an emitting layer (second conductive waveguide layer ) on top of, Al g Ga (1-g) The interface may have a gradient portion containing N (0.1 ≤ g ≤ 1) where the Al composition g increases as it moves away from the nitride semiconductor substrate. By providing an interface gradient portion like that of this embodiment, world This is mitigated, and the deterioration-inhibiting effect is improved. Furthermore, the film thickness of the interface gradient portion is preferably 2 nm to 5 nm, and more preferably 2 nm to 3 nm. In this case, the degradation suppression effect is further improved.

[0048] <Second conductive contact layer> The semiconductor laminate of the laser diode in this embodiment may further include a second conductivity type contact layer disposed on a second conductivity type cladding layer. The nitride semiconductor constituting the second conductivity type contact layer is preferably formed from, for example, GaN, AlN, or InN, and mixed crystals containing them, and more preferably from a nitride semiconductor containing GaN.

[0049] In the case of a p-type contact layer, the second conductive contact layer may contain impurities such as P, As, Sb, and other Group V elements other than N, as well as C, H, F, O, Mg, Si, and Be. Due to the versatility of the source gas, the impurity contained in the second conductive contact layer is preferably Mg. From the viewpoint of reducing contact resistance, the concentration of Mg is 8 × 10⁻⁶. 19 cm -3 The above 5 x 10 21 cm -3 The following is preferable: 5 × 10 20 cm -3 The above 5 x 10 21 cm -3 The following is more preferable:

[0050] Furthermore, the thickness of the second conductive contact layer is preferably between 1 nm and 20 nm. The thinner the second conductive contact layer, the better the carrier implantation efficiency of the light-emitting layer; conversely, the thicker the layer, the worse the carrier implantation efficiency.

[0051] <Electronic Block Layer> The semiconductor laminate of the laser diode in this embodiment may further have an electron blocking layer above the light-emitting layer, the electron blocking layer having a band gap larger than that of the light-emitting layer. The electron blocking layer may be provided, for example, on top of the light-emitting layer, or it may be provided inside the second conductivity type waveguide layer, between the second conductivity type waveguide layer and the light-emitting layer, or between the second conductivity type waveguide layer and the second conductivity type cladding layer. The thickness of the electron blocking layer is preferably 30 nm or less, and more preferably 20 nm or less, so that carriers (holes) can easily quantum penetrate the electron blocking layer.

[0052] <Electrode> A laser diode can emit light or oscillate by injecting current through a second electrode placed on a second conductivity type cladding layer and a first electrode placed on a first conductivity type cladding layer. In this case, the first electrode is formed to be in electrical contact with the first conductivity type cladding layer, and the second electrode is formed to be in electrical contact with the second conductivity type cladding layer.

[0053] The first electrode can be placed, for example, on the back side of the substrate. Alternatively, the first electrode can be placed on the first conductivity type cladding layer that is exposed by removing the layer above the first conductivity type cladding layer of the semiconductor stack, for example, by chemical etching or dry etching. In other words, the first electrode is placed on a region in the first conductivity type cladding layer that does not form a mesa structure.

[0054] When the first conductive cladding layer is an n-type cladding layer, the first electrode is formed from metals such as Al, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zr, mixed crystals thereof, or conductive oxides such as ITO or Ga2O3. When the first conductive cladding layer is a p-type cladding layer, the first electrode is formed from metals such as Ni, Au, Pt, Ag, Rh, Pd, Pt, Cu, Al, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Co, Ir, Zr, mixed crystals thereof, or conductive oxides such as ITO or Ga2O3.

[0055] When the second conductive cladding layer is an n-type cladding layer, the second electrode is formed from metals such as Al, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zr, mixed crystals thereof, or conductive oxides such as ITO or Ga2O3. When the second conductive cladding layer is a p-type cladding layer, the second electrode is formed from metals such as Ni, Au, Pt, Ag, Rh, Pd, Pt, Cu, Al, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Co, Ir, Zr, mixed crystals thereof, or conductive oxides such as ITO or Ga2O3.

[0056] The arrangement regions and shapes of the first and second electrodes are not limited as long as electrical contact is obtained with the first conductivity type cladding layer and the second conductivity type cladding layer (or the second conductivity type contact layer if a second conductivity type contact layer is provided).

[0057] (1.2) Method for manufacturing nitride semiconductor laminates and nitride semiconductor devices The nitride semiconductor element, the laser diode, in this embodiment can be manufactured by fractionating a nitride semiconductor laminate, which is produced through a process of forming each layer of the nitride semiconductor layer on a substrate. Below, a method for manufacturing a nitride semiconductor laminate and a method for manufacturing a laser diode as an example of a nitride semiconductor element will be described.

[0058] (1.2.1) Method for manufacturing nitride semiconductor laminates (Formation of substrate) The substrate is formed by general substrate growth methods such as sublimation, hydride vapor phase epitaxy (HVPE), and liquid phase epitaxy.

[0059] (Formation of semiconductor stack layers) Each layer of the semiconductor laminate formed on the substrate can be formed by, for example, molecular beam epitaxy (MBE), hydride vapor deposition (HVPE), or metal-organic chemical vapor deposition (MOCVD). Here, among the layers formed on the substrate, the nitride semiconductor layer can be formed using, for example, an Al raw material containing trimethylaluminum (TMAl), a Ga raw material containing trimethylgallium (TMGa) or triethylgallium (TEGa), or an N raw material containing ammonia (NH3).

[0060] A semiconductor laminate layer is formed on the substrate. At this time, an organometallic gas is introduced into the semiconductor laminate layer formation space. First, a first conductivity type cladding layer containing a first conductivity type nitride semiconductor is formed on the substrate.

[0061] Next, after forming a first-conductivity-type waveguide layer made of a nitride semiconductor such as AlGaN on the first-conductivity-type clad layer, a light-emitting layer is formed of a nitride semiconductor (such as AlGaN) including one or more quantum wells. Subsequently, a second-conductivity-type waveguide layer made of a nitride semiconductor such as AlGaN is formed on the light-emitting layer.

[0062] At this time, the formation of the first-conductivity-type waveguide layer, the light-emitting layer, and the second-conductivity-type waveguide layer is preferably performed under conditions satisfying -2Tw + 2050 < Vw < -2Tw + 2350 (850 °C < Tw < 970 °C), where Tw is the wafer temperature and Vw is the reactor pressure. Thereby, a light-emitting layer in which Ga is unevenly distributed in the nitride semiconductor layer plane direction can be formed. ru Also, similarly, a first-conductivity-type waveguide layer and a second-conductivity-type waveguide layer in which Ga is unevenly distributed in the nitride semiconductor layer plane direction can be formed. By localizing carriers in this way, the recombination rate can be increased and the light-emitting efficiency can be enhanced.

[0063] Subsequently, a second-conductivity-type clad layer is formed on the second-conductivity-type waveguide layer. First, before forming a part of the second-conductivity-type clad layer, the inflow of the organometallic gas is temporarily stopped to interrupt the growth of the nitride semiconductor layer, and the film-forming conditions are changed. Subsequently, it is preferable to change the conditions to a wafer temperature of 900 °C or higher and 1000 °C or lower and a reactor pressure of 15 mbar or higher and 350 mbar or lower, resume the inflow of the organometallic gas, and form a part of the second-conductivity-type clad layer of a second-conductivity-type nitride semiconductor.

[0064] After forming a part of the second-conductivity-type clad layer, before forming the remaining part of the second-conductivity-type clad layer, the inflow of the organometallic gas is temporarily stopped again to interrupt the growth of the nitride semiconductor layer, and the film-forming conditions are changed. Next, the wafer temperature is changed to between 1030°C and 1100°C, and the reactor pressure is changed to between 15 mbar and 350 mbar. The inflow of organometallic gas is then resumed to form the remaining portion of the second conductive cladding layer.

[0065] By forming the first conductivity type cladding layer, the first conductivity type waveguide layer, the light-emitting layer, and the second conductivity type waveguide layer in the manner described above, the carrier recombination rate can be increased and point defects in each layer can be reduced, thereby suppressing degradation and improving light emission efficiency. Furthermore, by setting the wafer temperature during the formation of a portion of the second conductivity cladding layer to a lower temperature than the wafer temperature during the formation of the remaining portion of the second conductivity cladding layer, it is possible to form at least one region in the portion of the second conductivity cladding layer and the remaining portion of the second conductivity cladding layer in which the carbon or oxygen concentration profile decreases discontinuously as it moves away from the substrate. In other words, the portion of the second conductivity cladding layer can be formed to contain more carbon or oxygen than the remaining portion of the second conductivity cladding layer. This makes it possible to suppress degradation and improve injection efficiency in the second conductivity cladding layer at the same time. Furthermore, by setting the reactor pressure used when forming a portion of the second conductivity cladding layer to be lower than the reactor pressure used when forming the remaining portion of the second conductivity cladding layer, it is possible to form a portion of the second conductivity cladding layer that contains more carbon or oxygen impurities compared to the remaining portion of the second conductivity cladding layer.

[0066] Furthermore, by temporarily stopping the inflow of organometallic gas before forming a portion of the second conductivity type cladding layer, hydrogen and silicon are localized at the substrate-side interface of the second conductivity type cladding layer. This is because, for example, when hydrogen gas (H2) is used as the carrier gas, hydrogen (H) tends to localize in the uppermost layer of the nitride semiconductor layer where growth is interrupted (e.g., the interface between the second conductivity type waveguide layer and the second conductivity type cladding layer, and a portion of the second conductivity type cladding layer). As a result, the laser diode can further improve the degradation suppression effect of the second conductivity type cladding layer and the efficiency of carrier injection into the light-emitting layer.

[0067] Conventionally, interrupting the growth of a nitride semiconductor layer causes some elements (for example, Ga in the case of AlGaN) to be lost, so growth interruptions are avoided as much as possible. However, by actively introducing hydrogen through growth interruptions, hydrogen can be localized at the interface between the second conductivity type waveguide layer and the second conductivity type cladding layer, and in a part of the second conductivity type cladding layer, thereby eliminating point defects at the interface. III By compensating to achieve -H3, the degradation suppression effect can be improved. Furthermore, conventionally, when the second conductivity type cladding layer is a p-type semiconductor layer, it is preferable that it does not contain silicon, which is an n-type impurity. However, by actively introducing silicon by interrupting growth, and localizing silicon derived from the raw materials or susceptor at the interface between the second conductivity type waveguide layer and the second conductivity type cladding layer, and in a part of the second conductivity type cladding layer, it is possible to compensate for point defects at the interface and improve the degradation suppression effect.

[0068] As described above, in this embodiment, the wafer temperature when forming a portion of the second conductivity type cladding layer is lower than the wafer temperature when forming the remaining portion of the second conductivity type cladding layer, thereby creating at least one region in the portion of the second conductivity type cladding layer and the remaining portion of the second conductivity type cladding layer in which the carbon or oxygen concentration profile decreases discontinuously as it moves away from the substrate. However, the manufacturing method is not limited to this. For example, the flow rate of the organometallic gas may be intentionally changed during the formation of the second conductivity type cladding layer to create a region in which the carbon or oxygen concentration profile decreases discontinuously as it moves away from the substrate.

[0069] Furthermore, if necessary, an intermediate layer may be formed between the second conductivity type cladding layer and the second conductivity type waveguide layer using a nitride semiconductor such as AlGaN, a second conductivity type contact layer may be provided on the second conductivity type cladding layer using a nitride semiconductor such as GaN, and an electron blocking layer may be formed above the light-emitting layer.

[0070] (1.2.2) Method for manufacturing nitride semiconductor devices (laser diodes) (Formation of mesa structures) Laser diodes are manufactured through a process (mesa structure formation process) in which unwanted portions of each layer of a semiconductor laminate formed on a substrate are removed by etching to form a semiconductor laminate. The removal of unwanted portions of each layer of the semiconductor laminate can be performed, for example, by inductively coupled plasma (ICP) etching. In the mesa structure formation process, etching is performed half By removing the unnecessary portions of each layer in the conductive laminate, a portion of the first conductive cladding layer is exposed.

[0071] (Formation of electrodes) Furthermore, laser diodes can be manufactured through a process of forming electrodes. Electrodes such as the first and second electrodes are formed by various methods of depositing metal by electron beam deposition (EB), such as resistance heating deposition, electron gun deposition, or sputtering, but are not limited to these methods. Each electrode may be formed as a single layer or as multiple layers stacked together. Furthermore, each electrode may be heat-treated in an oxygen, nitrogen, or air atmosphere after the formation of the metal layer.

[0072] (singularization) Finally, the substrate, with each layer formed through the process described above, is divided into individual pieces by dicing to manufacture nitride semiconductor devices (laser diodes).

[0073] Specifically, a first electrode is formed on the surface of the first conductivity type cladding layer. The second electrode is part of the semiconductor stack. to The electrodes are formed on the uppermost layer of the mesa structure (for example, the second conductive cladding layer). The formed electrodes are alloyed by heating with an infrared lamp using a rapid thermal annealing (RTA) device, or by laser annealing using laser pulses, thereby achieving contact with the semiconductor laminate. At this time, the alloying method is not particularly limited as long as sufficient contact with the semiconductor laminate is achieved. Thus, the laser diode manufactured by the nitride semiconductor device manufacturing method according to this embodiment can increase carrier injection efficiency and enhance light emission intensity.

[0074] (1.3) Measurement methods for the physical properties of laser diodes, etc. The physical properties of the laser diode described above can be measured as follows.

[0075] (Method for measuring layer thickness) The thickness of each layer constituting a laser diode can be measured by cutting a predetermined cross-section perpendicular to the substrate, observing this cross-section with a transmission electron microscope (TEM), and using the TEM's length-measuring function. The measurement method involves first observing a cross-section perpendicular to the main surface of the laser diode substrate using a TEM. Specifically, for example, the observation width is defined as a range of 2 μm or more in the direction parallel to the main surface of the substrate within the TEM image showing the cross-section perpendicular to the main surface of the laser diode substrate. Within this observation width, contrast is observed at the interface between two layers with different compositions; therefore, the thickness up to this interface is observed in a continuous observation area with a width of 200 nm. The average thickness of each layer within this 200 nm observation area is then calculated from five arbitrarily selected locations within the aforementioned observation width of 2 μm or more, thereby obtaining the thickness of each layer.

[0076] (Measurement of impurity and doping concentrations) The concentrations of dopants and impurities in each layer that makes up a laser diode can be measured by secondary ion mass spectrometry (SIMS). When measuring the concentration of dopants and impurities in each layer using SIMS after the device has been fabricated, the measurement can be performed after the electrodes have been removed by chemical etching or physical polishing. Alternatively, the concentration of dopants and impurities in each layer can also be measured by sputtering from the substrate side where electrodes are not formed. Specifically, SIMS measurements will be performed using measurement conditions provided by Evans Analytical Group (EAG). A cesium (Cs) ion beam with an energy of 14.5 keV will be used to sputter the sample during measurement.

[0077] (Method for measuring atomic concentration in each layer) One method for measuring the atomic concentration in each layer constituting a laser diode is reciprocal space mapping (RSM) using X-ray diffraction (XRD). Specifically, by analyzing the reciprocal space mapping data near the diffraction peak obtained using an asymmetric plane as the diffraction plane, the lattice relaxation rate and Al composition relative to the substrate can be obtained. Examples of diffraction planes include the (10-15) plane and the (20-24) plane.

[0078] Furthermore, layers and regions where sufficient reflectance cannot be obtained by XRD, such as the emissive layer, gradient layers, and hillocks formed in each layer, can be measured by X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX), and electron energy-loss spectroscopy (EELS).

[0079] EELS analyzes the composition of a sample by measuring the energy lost when an electron beam passes through the sample. Specifically, for example, in thinned samples used for TEM observation, the energy loss spectrum of the transmitted electron beam intensity is measured and analyzed. By utilizing the fact that the peak position that appears around 20 eV of energy loss changes according to the composition of each layer, the composition can be determined from the peak position.

[0080] Similar to the layer thickness calculation method using TEM observation described above, the average value of the Al composition in an observation width of 200 nm is calculated from five locations arbitrarily selected from the observation area of ​​2 μm or more, thereby obtaining the Al composition of each layer.

[0081] In EDX, characteristic X-rays generated by the electron beam in the thinned sample used for TEM observation as described above are measured and analyzed. Similar to the layer thickness calculation method using TEM observation described above, the average value of the Al composition at an observation width of 200 nm is calculated from five locations arbitrarily selected from the observation area of ​​2 μm or more, thereby obtaining the Al composition of each layer.

[0082] XPS allows for depth-direction evaluation by performing XPS measurements while sputter etching using an ion beam. While Ar+ is commonly used as the ion beam, other ion species, such as Ar cluster ions, can be used as long as they can be irradiated by the etching ion gun mounted on the XPS apparatus. The depth-direction distribution of the Al composition in each layer is obtained by measuring and analyzing the XPS peak intensities of Al, Ga, and N. Alternatively, instead of sputter etching, a laser diode can be obliquely polished so that a cross-section perpendicular to the main surface of the substrate is magnified and exposed, and the exposed cross-section can be measured with XPS.

[0083] The composition of each layer can be measured not only using XPS but also using Auger electron spectroscopy (AES). In this case, the composition can be measured by performing Auger electron spectroscopy on a cross-section exposed by sputter etching or oblique polishing. Furthermore, the composition of each layer can also be measured by SEM-EDX measurement on a cross-section exposed by oblique polishing.

[0084] (Method for measuring potential fluctuations) α, which indirectly represents potential fluctuations, is calculated using the equation FWHM(meV) = αx + 10meV, where x is the Al composition of the nitride semiconductor layer and FWHM is the full width at half maximum at the emission wavelength. Specifically, FWHM is obtained from the emission spectrum obtained by performing photoluminescence measurements on the nitride semiconductor layer. Furthermore, α can be obtained using x, the Al composition of the nitride semiconductor layer. In this case, the photoluminescence measurement uses a light source with a wavelength shorter than the band gap of the nitride semiconductor layer being excited. For example, 3 times the wavelength of a 213nm YAG light. wave Lasers and other devices are used. By measuring while cooling the sample to below 10K, it becomes possible to obtain more accurate values. Also, if there is a layer with a smaller band gap than the nitride semiconductor layer to be excited, the specific layer can be measured by removing it through etching or other methods. Specifically, if an emissive layer exists on top of the first conductivity type waveguide layer, the quantized emissive layer is excited by the excitation light, so an accurate value can be obtained by etching away the emissive layer and then measuring the first conductivity type waveguide layer.

[0085] (Method for measuring surface shape) Methods for measuring the surface morphology of the second type of conductive cladding layer include scanning electron microscopy (SEM) and atomic force microscopy (AFM). Specifically, the surface of the second conductive cladding layer is observed using a Hitachi High-Tech SU9000 scanning electron microscope at an acceleration voltage of 30kV. At this time, the magnification is set to 10 k ~50 k By doubling the size, the surface shape of the second conductive cladding layer can be clearly observed. Under these conditions, the number of spiral step terrace structures included within the observation range is measured, and the value obtained by dividing this by the area is taken as the density of spiral step terrace structures. The step height of the spiral step terrace structure on the surface of the second conductive cladding layer can be measured by AFM. Specifically, observation is performed using a scanning probe microscope manufactured by Hitachi High-Tech Corporation. During observation with the scanning probe microscope, the AFM mode is used to observe a 2 μm square area. The obtained AFM image The step height can be determined from this.

[0086] (Application fields of nitride semiconductor devices) The laser diodes relating to this disclosure are applicable to devices in fields such as medicine and life sciences, environmental science, industry, consumer electronics, agriculture, and other fields. The laser diodes are applicable to synthesis and decomposition equipment for pharmaceuticals or chemical substances, sterilization equipment for liquids, gases, and solids (containers, food, medical devices, etc.), cleaning equipment for semiconductors, surface modification equipment for films, glass, metals, etc., exposure equipment for the manufacture of semiconductors, FPDs (Flat Panel Displays), PCBs (Printed Wiring Boards), and other electronic products, printing and coating equipment, bonding and sealing equipment, transfer and molding equipment for films, patterns, mockups, etc., and measurement and inspection equipment for banknotes, scratches, blood, chemical substances, etc.

[0087] Examples of liquid sterilization equipment include, but are not limited to, automatic ice makers, ice trays and storage containers in refrigerators, water tanks for ice makers, freezers, ice makers, humidifiers, dehumidifiers, cold water tanks, hot water tanks and flow piping for water dispensers, stationary water purifiers, portable water purifiers, water dispensers, hot water heaters, wastewater treatment equipment, garbage disposals, toilet drain traps, washing machines, dialysis water sterilization modules, peritoneal dialysis connector sterilizers, and disaster relief water storage systems.

[0088] Examples of gaseous sterilization devices include, but are not limited to, air purifiers, air conditioners, ceiling fans, vacuum cleaners for floors or bedding, futon dryers, shoe dryers, washing machines, clothes dryers, indoor germicidal lamps, storage room ventilation systems, shoe boxes, chests of drawers, etc. Examples of solid sterilization equipment (including surface sterilization equipment) include, but are not limited to, vacuum packers, belt conveyors, hand tool sterilization equipment for medical, dental, barber, and beauty salon use, toothbrushes, toothbrush holders, chopstick cases, cosmetic pouches, drain covers, toilet bidet devices, and toilet lids.

[0089] 2. Second Embodiment A nitride semiconductor device according to a second embodiment of this disclosure will now be described. The nitride semiconductor device according to this embodiment is, for example, a light-emitting element. The following describes the case where a nitride semiconductor element is a light-emitting element.

[0090] (2.1) Structure of the light-emitting element The light-emitting element according to this embodiment includes a nitride semiconductor substrate containing Al and a semiconductor laminate disposed on the nitride semiconductor substrate. The semiconductor laminate includes a first-conductivity-type clad layer containing a nitride semiconductor of the first conductivity type, a light-emitting layer formed of a nitride semiconductor disposed on the first-conductivity-type clad layer and containing one or more quantum wells, and a second-conductivity-type clad layer formed of a nitride semiconductor containing Al of the second conductivity type and disposed on the light-emitting layer. At the interface on the nitride semiconductor substrate side of the second-conductivity-type clad layer, hydrogen is contained at 1×10 17 cm -3 or more and 5×10 19 cm -3 or less.

[0091] The light-emitting element of this embodiment is different from the laser diode of the first embodiment in that it does not include a first-conductivity-type waveguide layer and a second-conductivity-type waveguide layer. Further, in the light-emitting element according to this embodiment, the second-conductivity-type clad layer may be used as a barrier layer. Also, the light-emitting element of this embodiment has a configuration different from the first-conductivity-type clad layer of the laser diode of the first embodiment. Therefore, hereinafter, the first-conductivity-type clad layer and the second-conductivity-type clad layer of the light-emitting element will be described in detail. Note that each layer other than the first-conductivity-type clad layer, that is, the nitride semiconductor substrate, the buffer layer, and the light-emitting layer, is the same as each layer described in the first embodiment, and thus the description thereof is omitted.

[0092] <First-conductivity-type clad layer> The first-conductivity-type clad layer is a layer of a nitride semiconductor containing Al and Ga. The first-conductivity-type clad layer is formed of, for example, Al a Ga (1-a) N (0 < a < 1), and is preferably formed of, for example, Al a Ga (1-a) N (0.7 ≤ a ≤ 1). The first-conductivity-type clad layer is preferably formed of an n-type semiconductor. Furthermore, the film thickness T0 of the first conductive cladding layer is preferably 3300 × a - 2100 nm or more and 15700 × a - 10100 nm or less (where a is the ratio of Al atoms when the total number of group III atoms of the nitride semiconductor constituting the first conductive cladding layer is set to 1). Furthermore, the resistivity of the first conductive cladding layer is 1 × 10⁻⁶ -3 Ω · cm or more 5×10 -3 Ω · It is preferable that it be less than or equal to cm. Other than this, the configuration is the same as that of the first conductive cladding layer described in the first embodiment.

[0093] <Second conductive cladding layer> In light-emitting devices, instead of a second-conductivity cladding layer with a gradient of Al composition, an electron-blocking layer with a constant Al composition is provided on the light-emitting layer, and a second-conductivity contact layer with a gradient of Al composition is provided on top of the electron-blocking layer. This electron-blocking layer and the second-conductivity contact layer with a gradient of Al composition together serve as the cladding layer. In this case, by growing the electron block layer at a lower temperature than conventional methods, it is possible to achieve both the effect of suppressing the degradation of the electron block layer and the second conductivity type contact layer, and the effect of improving the carrier injection efficiency into the light-emitting layer, similar to the laser diode according to the first embodiment. When the electron block layer and the second conductivity type contact layer are considered as a second conductivity type cladding layer, the inflow of organometallic gas is temporarily stopped before the growth of the electron block layer to interrupt the growth of the nitride semiconductor layer, and only a part of the electron block layer is grown at a low temperature. As a result, similar to the second conductivity type cladding layer of a laser diode, the concentration profile of carbon or oxygen decreases discontinuously, hydrogen is localized at the interface of the electron block layer on the light-emitting layer side, and a light-emitting element is obtained in which the electron block layer contains more impurities than conventional methods. Furthermore, by temporarily stopping the inflow of organometallic gas after the growth of the electron block layer and before the growth of the second conductivity type contact layer, thereby interrupting the growth of the nitride semiconductor layer, it becomes possible to include hydrogen at a higher concentration in the region of the second conductivity type cladding layer (the layer combining the electron block layer and the second conductivity type contact layer) that is separated from the nitride semiconductor substrate by the thickness of the electron block layer, compared to other regions.

[0094] The thickness of the electron blocking layer is preferably 10 nm or more and 15 nm or less. That is, in the light-emitting element, the region in which the concentration profile of carbon or oxygen contained in the electron blocking layer decreases discontinuously is preferably located in the region of 10 nm or more and 15 nm or less from the substrate side of the electron blocking layer.

[0095] Unlike the laser diode according to the first embodiment, the light-emitting element according to this embodiment does not have a first conductivity type waveguide layer and a second conductivity type waveguide layer. Therefore, it is difficult to evaluate α, which indirectly represents potential fluctuations. This is because when attempting to evaluate α, which indirectly represents potential fluctuations, the quantized light-emitting layer is excited, and the correct results cannot be obtained. However, by forming a nitride semiconductor layer under the same conditions as in the first embodiment, it is possible to form a nitride semiconductor layer having α, which indirectly represents similar potential fluctuations.

[0096] 3. Specific Examples of Nitride Semiconductor Devices The nitride semiconductor device of this embodiment will be described in more detail below with reference to Figures 4 to 7. The detailed configuration of each layer in each of the following examples is as described above.

[0097] (3.1) Example 1 Figure 4 is a schematic cross-sectional view of a laser diode 1, which is the first example. As shown in Figure 4, the laser diode 1 comprises a substrate 11, a semiconductor laminate 10 disposed on the substrate, a first electrode 13, and a second electrode 14. The semiconductor laminate 10 comprises a first conductivity type cladding layer 101 having an n-type conductivity, a first conductivity type waveguide layer 102, an emitting layer 103, a second conductivity type waveguide layer 104, and a second conductivity type cladding layer 105 having a p-type conductivity.

[0098] (3.2) Second example Figure 5 is a schematic cross-sectional view of a laser diode 2, which is a second example. As shown in Figure 5, the laser diode 2 comprises a substrate 11, a buffer layer 12, a semiconductor laminate 10 disposed on the substrate 11 (buffer layer 12), a first electrode 13, and a second electrode 14. The semiconductor laminate 10 comprises a first conductivity type cladding layer 101 having an n-type conductivity, a first conductivity type waveguide layer 102, an emitting layer 103, a second conductivity type waveguide layer 104, and a second conductivity type cladding layer 105 having a p-type conductivity. In other words, laser diode 2 differs from laser diode 1 in that it has a buffer layer 12.

[0099] (3.3) Third example Figure 6 is a schematic cross-sectional view of a laser diode 3, which is a third example. As shown in Figure 6, the laser diode 3 is connected to the substrate 11 and 、 The semiconductor laminate 10 comprises a semiconductor laminate 10 arranged on a substrate, a first electrode 13, and a second electrode 14. The semiconductor laminate 10 includes a first conductivity type cladding layer 101 having an n-type conductivity, a first conductivity type waveguide layer 102, an emissive layer 103, a second conductivity type waveguide layer 104, a second conductivity type cladding layer 105 having a p-type conductivity, and a contact layer 106. In other words, laser diode 3 differs from laser diode 1 in that it has a contact layer 106. The laser diode of this disclosure may also be configured to include the buffer layer 12 described in the second example and the contact layer 106 described in the third example.

[0100] (3.4) Fourth example Figure 7 shows the 4 This is a schematic cross-sectional view of a light-emitting element 4, which is an example of such an element. As shown in Figure 7, the light-emitting element 4 comprises a substrate 11, a semiconductor laminate 10 disposed on the substrate, a first electrode 13, and a second electrode 14. The semiconductor laminate 10 comprises a first conductivity type cladding layer 101 having an n-type conductivity, a light-emitting layer 103, and a second conductivity type cladding layer 105 having a p-type conductivity. In the light-emitting element 4, an electron blocking layer and a second conductivity type contact layer are provided and perform the role of the second conductivity type cladding layer 105. In other words, the light-emitting element 4 differs from the laser diode 1 in that it does not have a first conductivity type waveguide layer 102 and a second conductivity type waveguide layer 104. Furthermore, the light-emitting element 4 differs from the laser diode 1 in that it is provided with an electron blocking layer and a second conductivity type contact layer which function as a second conductivity type cladding layer 105. The light-emitting element of this disclosure may also have a configuration that includes the buffer layer 12 described in the second example.

[0101] 4. Effects The nitride semiconductor device described above has the following effects.

[0102] (1) The nitride semiconductor device of the present disclosure comprises an Al-containing nitride semiconductor substrate and a semiconductor laminate disposed on the nitride semiconductor substrate, wherein the semiconductor laminate has a first conductivity type cladding layer containing a first conductivity type nitride semiconductor, an emissive layer disposed on the first conductivity type cladding layer and formed of a nitride semiconductor containing one or more quantum wells, and a second conductivity type cladding layer disposed on the emissive layer and formed of a second conductivity type Al-containing nitride semiconductor, wherein the region of the second conductivity type cladding layer from the nitride semiconductor substrate side to 110 nm contains hydrogen at a higher concentration than other regions of the second conductivity type cladding layer. This makes it possible to achieve both the effect of suppressing the degradation of the second conductive cladding layer and the effect of improving the carrier injection efficiency into the light-emitting layer.

[0103] (2) In the nitride semiconductor device of the present disclosure, hydrogen is present at the interface of the second conductive cladding layer on the nitride semiconductor substrate side, with a concentration of 1 × 10⁻¹⁶ hydrogen atoms. 17 cm -3 The above 5 x 10 19 cm -3 The following are preferably included: This makes it possible to suppress the degradation of the second conductivity type cladding layer without hindering the improvement of the carrier injection efficiency into the light-emitting layer.

[0104] (3) In the nitride semiconductor device of the present disclosure, it is preferable that the compositional discontinuity region has a compositional gradient in which the Al composition d increases by 0.002 or more and 0.05 or less as it moves away from the nitride semiconductor substrate. This makes it possible to better achieve both the effect of suppressing the degradation of the second conductive cladding layer and the effect of improving the efficiency of carrier injection into the light-emitting layer.

[0105] (4) The method for manufacturing a nitride semiconductor laminate according to the present disclosure involves forming a first conductivity type cladding layer containing a first conductivity type nitride semiconductor on an Al-containing nitride semiconductor substrate, forming an emissive layer on the first conductivity type cladding layer using a nitride semiconductor containing one or more quantum wells, forming a portion of a second conductivity type cladding layer containing a second conductivity type nitride semiconductor under conditions where the wafer temperature is 900°C or more and 1000°C or less and the reactor pressure is 15 mbar or more and 350 mbar or less, and forming the remaining portion of the second conductivity type cladding layer under conditions where the wafer temperature is 1030°C or more and 1100°C or less and the reactor pressure is 15 mbar or more and 350 mbar or less, thereby forming a semiconductor laminate on the nitride semiconductor substrate. This allows a portion of the second conductive cladding layer to contain more carbon or oxygen compared to the remaining portion, thereby achieving both suppression of degradation and improvement of injection efficiency in the second conductive cladding layer.

[0106] (5) In the method for manufacturing a nitride semiconductor laminate according to the present disclosure, it is preferable that the reactor pressure when forming a part of the second conductivity type cladding layer is 15 mbar or more and 100 mbar or less. This allows a portion of the second conductive cladding layer to contain more carbon or oxygen compared to the remaining portion of the second conductive cladding layer, thereby improving the degradation suppression effect and injection efficiency in the second conductive cladding layer.

[0107] (6) In the method for manufacturing a nitride semiconductor laminate according to the present disclosure, it is preferable to introduce an organometallic gas when forming the first conductivity type cladding layer, the light-emitting layer and the second conductivity type cladding layer, to temporarily stop the inflow of the organometallic gas after forming the light-emitting layer but before forming a part of the second conductivity type cladding layer, and to temporarily stop the inflow of the organometallic gas after forming a part of the second conductivity type cladding layer but before forming the remaining part of the second conductivity type cladding layer. This temporarily interrupts the growth of the nitride semiconductor layer, localizing hydrogen and silicon at the substrate-side interface of the second-conductivity cladding layer. This further enhances the degradation suppression effect of the second-conductivity cladding layer and the efficiency of carrier injection into the light-emitting layer. [Examples]

[0108] <Sample 1> The laser diodes of this disclosure will be described below with reference to examples and comparative examples. However, the laser diodes of this disclosure are not limited to these examples. A 550 μm thick (0001) plane AlN single crystal substrate was used as the substrate. Next, a homoepitaxial AlN layer was formed on the substrate. The AlN layer was formed to a thickness of 500 nm under conditions of 1200°C. At this time, the ratio of the supply rate of Group III element raw material gas to the supply rate of nitrogen raw material gas (V / III ratio) was set to 50. The growth rate of the AlN layer at this time was 0.5 μm / hr. Trimethylaluminum (TMAl) was used as the Al raw material, and ammonia (NH3) was used as the N raw material.

[0109] A first conductivity type cladding layer was formed on this substrate. The first conductivity type cladding layer is an n-type AlGaN layer (Al: 75%, i.e., Al) using Si as a dopant impurity.0.75 Ga 0.25 The N layer was used. The first conductive cladding layer was formed to a thickness of 400 nm at a temperature of 1050°C, with a reactor pressure of 50 mbar and a V / III ratio of 4000. The growth rate of the first conductive cladding layer at this time was 0.4 μm / hr. Trimethylaluminum (TMAl) was used as the Al raw material. Triethylgallium (TEGa) was used as the Ga raw material. Ammonia (NH3) was used as the N raw material. Monosilane (SiH4) was used as the Si raw material.

[0110] Next, the first conductive cladding layer Conductive type An n-type waveguide layer was formed. The n-type waveguide layer is an n-type AlGaN layer (Al: 63%, i.e., Al) using Si as a dopant impurity. 0.63 Ga 0.37 The n-type waveguide layer was formed to a thickness of 40 nm at a temperature of 950°C, with a reactor pressure of 300 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. Furthermore, trimethylaluminum (TMAl) was used as the Al raw material. Triethylgallium (TEGa) was used as the Ga raw material. Ammonia (NH3) was used as the N raw material.

[0111] Next, an emissive layer was formed on the n-type waveguide layer. The emissive layer was formed by depositing a film to have a multiple quantum well structure in which a quantum well layer and a barrier layer are stacked in two periods. Here, the quantum well layer is an AlGaN layer with a thickness of 4.5 nm (Al: 52%, i.e., Al 0.52 Ga 0.48 The N layer was made of AlGaN (Al: 63%, i.e., Al 0.63 Ga 0.37 (N layers) The light-emitting layer was formed at a temperature of 950°C, with a reactor pressure of 300 mbar and a V / III ratio of 4000. The growth rate of the quantum well layer at this time was 0.18 μm / hr. The growth rate of the barrier layer was 0.15 μm / hr.

[0112] Next, the second layer is placed on the light-emitting layer. Conductive type A p-type waveguide layer was formed. The p-type waveguide layer is an AlGaN layer that does not contain dopants (Al: 63%, i.e., Al 0.63 Ga 0.37 The p-type waveguide layer was formed to a thickness of 70 nm at a temperature of 950°C, with a reactor pressure of 300 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. Trimethylaluminum (TMAl) was used as the Al raw material, and triethylgallium (TEGa) was used as the Ga raw material.

[0113] Next, a second conductivity type cladding layer was formed on the p-type waveguide layer. The second conductivity type cladding layer is a composition gradient layer in which the Al composition is gradient. The second conductivity type cladding layer consists of a 2.5 nm thick AlGaN layer (interface gradient portion) in which the Al composition is distributed in the direction away from the substrate, changing from Al=0.63 to 1.0, and a 330 nm thick p-type AlGaN layer in which the Al composition is distributed in the direction away from the substrate, changing from Al=1.0 to 0.7. Before growing the second conductive cladding layer, the inflow of organometallic gas was temporarily stopped, and the reactor pressure was set to 50 mbar at a temperature of 950°C while irradiating with only hydrogen and NH3. The first layer (A), with a thickness of 72.5 nm and an Al composition of 0.63 → 1.0 → 0.95 (formed from the interface gradient and a portion of the second conductive cladding layer), was formed under conditions of a V / III ratio of 4000. The growth rate at this time was 0.3~0.5 μm / hr. Here, layer (A) is a layer formed from the interface gradient and a portion of the second conductive cladding layer. Of the 72.5 nm thick layer (A), the region with an Al composition of 0.63 → 1.0 and a thickness of 2.5 nm is the "interface gradient," and the remaining region with an Al composition of 1.0 → 0.95 and a thickness of 70 nm is the "part of the second conductive cladding layer." Furthermore, the "interface gradient region" is also a region included in the second conductive cladding layer.

[0114] Next, the inflow of organometallic gas was temporarily stopped, and the reactor pressure was set to 50 mbar at a temperature of 1050°C while irradiating with only hydrogen and NH3. The remaining layer (B) (part of the remaining second conductive cladding layer), with a thickness of 257.5 nm and an Al composition of 0.98 → 0.7, was formed under conditions of a V / III ratio of 4000. The growth rate at this time was 0.3~0.5 μm / hr. Furthermore, trimethylaluminum (TMAl) was used as the Al raw material throughout the process. Triethylgallium (TEGa) was used as the Ga raw material. The interface between layer (A) and layer (B) described above corresponds to region P where the impurity concentration profile changes abruptly, or to a compositional discontinuity region Q where the Al composition is discontinuous in the direction away from the substrate.

[0115] Next, 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 from an AlGaN layer and a GaN layer. The AlGaN layer was a 30 nm thick p-type nitride semiconductor layer in which Mg was used as a dopant impurity, and the Al composition was distributed in the direction away from the substrate, changing from Al=0.7 to 0.4. The GaN layer was formed from GaN (i.e., Al:0%) with a thickness of 10 nm. The p-type contact layer was formed under the conditions that the reactor pressure was set to 150 mbar, the V / III ratio was 3650, and the temperature was 950 °C. The growth rate of the p-type contact layer at this time was 0.2 μm / hr.

[0116] Various analyses were performed on the nitride semiconductor laminate obtained as described above. As a result, the region where the Al composition at the interface between the well layer and the barrier layer in the light-emitting layer was inclined was 0.5 nm. α, which indirectly represents potential fluctuation, was 146 meV. Next, a discontinuity in the Al composition was observed at the interface between the p-type cladding layers (A) and (B), and the starting composition of (B) was 3% higher than that of (A). Also, at the interface between (A) and (B), hydrogen was 5×10 18 cm -3 , Si was 5×10 18 cm -3 were observed. The FWHM of the hydrogen peak at this time was 7.5 nm. Similarly, more oxygen and carbon were detected in (A) than in (B), and the concentration profile changed discontinuously at the interface between (A) and (B). The oxygen concentration and carbon concentration at this time were 3×10 17 cm -3 and 3×10 17 cm -3 respectively. Also, the p-type contact layer was removed with SF6 gas, and the surface was observed. As a result, the surface shape had a spiral step terrace structure based on a hexagon, and the step Terrace structure height was 0.3 nm, and the step Terrace structure density was 5×10 7 cm -2 .

[0117] The semiconductor laminate portion formed as described above was annealed in a N2 atmosphere at 700 °C for 10 minutes or more to further reduce the resistance of the p-type contact layer. A mesa structure in which the n-type cladding layer was exposed was formed by performing dry etching with a gas containing Cl2 using ICP. The formed mesa structure 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 a plan view, and the length in the <11-20> direction is the distance between the sides of the mesa structure.

[0118] In the mesa structure, Ni and Au were sequentially deposited in a long rectangular shape in the <1-100> direction on the second conductive contact layer to form multiple electrode metal regions, creating 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 was exposed, V, Al, Ni, Ti, and Au were sequentially deposited in a long rectangular shape in the <1-100> direction to form multiple electrode metal regions, creating an n-type first electrode. Using an RTA apparatus, the first and second electrodes were annealed at 550°C for 60 seconds under a nitrogen atmosphere. Furthermore, by performing multiple cleavage operations parallel to the <11-20> direction within the electrode metal region, the substrate was divided into stripes, forming individual laser diodes. The length of the mesa structure in the <1-100> direction after division was 600 μm. When the laser diode obtained in this manner was subjected to current injection and current-endface emission intensity measurement, the threshold voltage was found to be 8V and the oscillation threshold current was 3kA / cm². 2 The oscillation time at that time was 100 seconds.

[0119] <Sample 2> ~ <Sample 4> Laser diodes for Samples 2 to 4 were formed in the same manner as Sample 1, except that the Al composition of the n-type AlGaN layer, which uses Si as a dopant impurity to constitute the first conductive cladding layer, was changed as shown in Table 1.

[0120] <Sample 5> to <Sample 8> Laser diodes for Samples 5 to 8 were formed in the same manner as for Sample 1, except that the film thickness of the first conductive cladding layer was varied as shown in Table 1.

[0121] <Sample 9> to <Sample 25> Light-emitting layer and first conductive waveguide layer Laser diodes for Samples 9 to 25 were formed in the same manner as Sample 1, except that the wafer temperature and reactor pressure during nitride semiconductor layer growth when forming the second conductivity type waveguide layer were changed as shown in Table 1. Note that the growth temperature and growth pressure listed in the light-emitting layer section of Table 1 are for the light-emitting layer and the first Conductive type Waveguide layer and second Conductive type Temperature during waveguide layer formation and pressure The first at this time Conductive type The values ​​of α, which indirectly represent the potential fluctuations of the waveguide layer, are shown in Table 1.

[0122] <Sample 26> A laser diode for Sample 26 was formed in the same manner as for Sample 1, except that the wafer temperature during nitride semiconductor layer growth during the formation of the second conductivity type cladding layer was changed as shown in Table 1. The degree of discontinuity at the discontinuity point of the Al composition and the concentration of carbon or oxygen in the second conductivity type cladding layer were as shown in Table 1.

[0123] <Sample 27> ~ <Sample 29> Laser diodes for samples 27 to 29 were formed in the same manner as for sample 1, except that the reactor pressure during nitride semiconductor layer growth was changed as shown in Table 2 when a portion of the second conductivity type cladding layer was formed on the substrate side. The degree of discontinuity at the discontinuity point of the Al composition and the concentration of carbon or oxygen contained in the second conductivity type cladding layer were as shown in Table 2.

[0124] <Sample 30> ~ <Sample 32> Laser diodes for samples 30 to 32 were formed in the same manner as for sample 1, except that the wafer temperature during nitride semiconductor layer growth during the formation of the remaining portion of the second conductivity type cladding layer was changed as shown in Table 2. The degree of discontinuity at the discontinuity point of the Al composition and the concentration of carbon or oxygen in the second conductivity type cladding layer were as shown in Table 2.

[0125] <Sample 33> ~ <Sample 35> Laser diodes for samples 33 to 35 were formed in the same manner as for sample 1, except that the reactor pressure during nitride semiconductor layer growth during the formation of the remaining portion of the second conductivity type cladding layer was changed as shown in Table 2. The degree of discontinuity at the discontinuity point of the Al composition and the concentration of carbon or oxygen in the second conductivity type cladding layer were as shown in Table 2.

[0126] <Sample 36> ~ <Sample 39> Laser diodes for samples 36 to 39 were formed in the same manner as for sample 1, except that the thickness of the remaining portion of the second conductivity cladding layer was varied to change the overall film thickness of the second conductivity cladding layer as shown in Table 2. The degree of discontinuity at the point of discontinuity in the Al composition and the concentration of carbon or oxygen contained in the second conductivity cladding layer were as shown in Table 2.

[0127] <Sample 40> ~ <Sample 41> Laser diodes for samples 40 to 41 were formed in the same manner as for sample 1, except that the thickness of the composition gradient layer formed between the second conductivity waveguide layer and the second conductivity cladding layer was varied as shown in Table 2.

[0128] <Sample 42> ~ <Sample 46> Laser diodes for samples 42 to 46 were formed in the same manner as for sample 1, except that the thickness of a portion of the substrate-side second conductivity cladding layer where the Al composition decreases was varied to 30 nm, 5 nm, 2 nm, 110 nm, and 150 nm, and the thickness of the remaining portion of the second conductivity cladding layer was varied so that the total film thickness of the second conductivity cladding layer was 330 nm. Here, the thickness of a portion of the substrate-side second conductivity cladding layer is the distance from the substrate side to the region where the Al composition becomes discontinuous, or where the concentration profile of carbon or oxygen decreases discontinuously.

[0129] <Sample 47> ~ <Sample 50> Laser diodes for samples 47 to 50 were formed in the same manner as for sample 1, except that the hydrogen concentration in a portion of the substrate side of the second conductive cladding layer was changed by varying the growth interruption time.

[0130] <Sample 51> The laser diode of sample 51 was formed in the same manner as sample 1, except that the growth of the nitride semiconductor layer was not interrupted before or after forming a portion of the substrate side of the second conductivity type cladding layer.

[0131] <Sample 52> The laser diode of sample 52 was formed in the same manner as sample 1, except that a predetermined amount of Ga was continuously supplied during growth interruption, and the second conductivity type cladding layer was formed so that there were no discontinuities in Al composition at the interface between a portion of the substrate side of the second conductivity type cladding layer and the remaining portion.

[0132] [Table 1]

[0133] [Table 2]

[0134] As shown in Tables 1 and 2, for samples 1 to 50, the growth of the nitride semiconductor layer was interrupted before and after the formation of a portion of the substrate side of the second conductivity type cladding layer. Laser diodes equipped with a second conductivity type cladding layer containing a higher concentration of hydrogen in the region from 1 nm to 110 nm from the nitride semiconductor substrate side compared to other regions showed improved threshold voltage and oscillation threshold voltage compared to the laser diode of sample 46, which does not have such a second conductivity type cladding layer. current density Overall, the performance decreased, and the oscillation time increased. This confirmed that both the suppression of cladding layer degradation and the improvement of carrier injection efficiency could be achieved.

[0135] While embodiments of the present disclosure have been described above, these embodiments are merely illustrative examples of apparatus and methods for realizing the technical concept of the present disclosure, and the technical concept of the present disclosure does not specify the material, shape, structure, arrangement, etc., of the components. The technical concept of the present disclosure can be modified in various ways within the technical scope defined by the claims described in the claims. [Explanation of Symbols]

[0136] 1,2,3 Laser Diodes 4 light-emitting elements 10 Semiconductor stacked section 11 circuit boards 12 buffer layers 13 1st electrode 14 2nd electrode 101 First conductive cladding layer 102 First Conductivity Waveguide Layer 103 Light-emitting layer 104 Second Conductive Waveguide Layer 105 Second conductive cladding layer 106 Contact Layer

Claims

1. Al-containing nitride semiconductor substrate, The semiconductor laminate is disposed on the nitride semiconductor substrate, The aforementioned semiconductor stacked portion is A first conductivity type cladding layer containing a first conductivity type nitride semiconductor, A light-emitting layer is disposed on the first conductive cladding layer and is made of a nitride semiconductor containing one or more quantum wells, The light-emitting layer is disposed on the aforementioned light-emitting layer and comprises a second conductivity type cladding layer made of a nitride semiconductor containing a second conductivity type Al, A nitride semiconductor device in which a region of the second conductivity type cladding layer from the nitride semiconductor substrate side, between 1 nm and 110 nm in length, contains hydrogen at a higher concentration than other regions of the second conductivity type cladding layer.

2. At the interface of the second conductive cladding layer on the nitride semiconductor substrate side, hydrogen is present in a quantity of 1 × 10⁻¹⁶. １７ cm －３ The above 5 x 10 １９ cm －３ The nitride semiconductor device according to claim 1, which includes the following:

3. The second conductive cladding layer is Al ｄ Ga （１－ｄ） The nitride semiconductor element according to claim 1, wherein N (0.1 ≤ d ≤ 1).

4. The nitride semiconductor element according to claim 1, wherein the half-width of the hydrogen concentration profile in the region of the second conductive cladding layer containing hydrogen at a higher concentration than other regions is 5 nm or more and 10 nm or less.

5. The nitride semiconductor device according to claim 1, wherein the nitride semiconductor substrate is an AlN single crystal substrate.

6. The first conductive cladding layer is Al ａ Ga （１－ａ） The nitride semiconductor element according to claim 1, formed with N (0.65 < a ≤ 0.9).

7. The nitride semiconductor device according to claim 1, wherein the thickness of the first conductive cladding layer is 250 nm or more and 800 nm or less.

8. A first conductive waveguide layer is disposed between the first conductive cladding layer and the light-emitting layer to confine light to the light-emitting layer, The nitride semiconductor element according to claim 1, further comprising a second conductive waveguide layer disposed between the second conductive cladding layer and the light-emitting layer to confine light to the light-emitting layer.

9. The second conductive contact layer is disposed on the second conductive cladding layer and is made of a nitride semiconductor containing GaN, The second conductive type clad layer is Al ｄ Ga （１－ｄ） N (0.1 ≦ d ≦ 1), and has a composition gradient in which the Al composition d decreases as it moves away from the nitride semiconductor substrate, and the nitride semiconductor device according to claim 3, wherein the film thickness is 500 nm or less.

10. The nitride semiconductor element according to claim 9, wherein the second conductive cladding layer has a composition gradient in which the Al composition d decreases in the range of 1 to 0.7 as it moves away from the nitride semiconductor substrate.

11. The nitride semiconductor element according to claim 2, wherein the film thickness of the second conductive cladding layer is 250 nm or more and 500 nm or less.

12. The nitride semiconductor element according to claim 1, wherein the film thickness T0 of the first conductive cladding layer is 3300 × a - 2100 nm or more and 15700 × a - 10100 nm or less (where a is the ratio of Al atoms when the total number of group III atoms of the nitride semiconductor constituting the first conductive cladding layer is set to 1.

13. The resistivity of the first conductive cladding layer is 1 × 10⁻⁶ －３ Ω・cm or more 5×10 －３ The nitride semiconductor element according to claim 12, wherein the value is Ω·cm or less.

14. A first conductivity type cladding layer containing a first conductivity type nitride semiconductor is formed on an Al-containing nitride semiconductor substrate. A light-emitting layer is formed on the first conductive cladding layer using a nitride semiconductor containing one or more quantum wells. Under conditions where the wafer temperature is 900°C or higher and 1000°C or lower, and the reactor pressure is 15 mbar or higher and 350 mbar or lower, a portion of the second conductivity type cladding layer containing a second conductivity type nitride semiconductor is formed. A method for manufacturing a nitride semiconductor laminate, comprising forming the remaining portion of the second conductive cladding layer on the nitride semiconductor substrate under the conditions that the wafer temperature is 1030°C or higher and 1100°C or lower, and the reactor pressure is 15 mbar or higher and 350 mbar or lower.

15. The method for manufacturing a nitride semiconductor laminate according to claim 14, wherein the reactor pressure when forming a part of the second conductive cladding layer is 15 mbar or more and 100 mbar or less.

16. During the formation of the first conductive cladding layer, the light-emitting layer, and the second conductive cladding layer, an organometallic gas is introduced. After forming the light-emitting layer, and before forming a portion of the second conductive cladding layer, the inflow of the organometallic gas is temporarily stopped. A method for manufacturing a nitride semiconductor laminate according to claim 14, wherein the inflow of the organometallic gas is temporarily stopped after forming a portion of the second conductive cladding layer and before forming the remaining portion of the second conductive cladding layer.

17. After forming the semiconductor laminate by the method for manufacturing a nitride semiconductor laminate according to any one of claims 14 to 16, Unnecessary portions of each layer of the semiconductor stack are removed by etching. An electrode is formed on the semiconductor stacked portion, A method for manufacturing a nitride semiconductor element, comprising dividing the nitride semiconductor substrate on which each layer of the semiconductor stack is formed into individual pieces by dicing.

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