METHOD FOR PRODUCE A NITRID SEMICONDUCTOR STACK AND NITRID SEMICONDUCTOR ELEMENT AND NITRID SEMICONDUCTOR ELEMENT

Abstract

A nitride semiconductor element is provided that is capable of achieving both cladding layer degradation suppression and carrier injection efficiency. A nitride semiconductor stack for forming a nitride semiconductor element is obtained by forming a first-conductivity-type cladding layer containing a first-conductivity-type nitride semiconductor on a nitride semiconductor substrate containing aluminum; forming a light-emitting layer using a nitride semiconductor containing one or more quantum wells on the first-conductivity-type cladding layer; and forming part of a second-conductivity-type cladding layer containing a second-conductivity-type nitride semiconductor.under conditions of a wafer temperature of 900 °C or more and 1000 °C or less and a reactor pressure of 15 mbar or more and 350 mbar or less, and forming a remaining part of the cladding layer of the second conductivity type under conditions of a wafer temperature of 1030 °C or more and 1100 °C or less and a reactor pressure of 15 mbar or more and 350 mbar or less, to form a semiconductor stack part on the nitride semiconductor substrate.

Description

Technical field

[0001] The present disclosure relates to a method for producing a nitride semiconductor stack and a nitride semiconductor element and a nitride semiconductor element. General state of the art

[0002] Nitride semiconductors are commonly used as materials for light-emitting diodes (LEDs), laser diodes (LDs), and similar devices. Nitride semiconductors exhibit a direct-junction recombination form and are therefore suitable for LEDs and LDs due to their high recombination efficiency and optical gain. As an example of a laser diode using such a nitride semiconductor, a technique is disclosed in which a current-injection laser diode is oscillated in the ultraviolet range (e.g., NPL 1). Bibliography Non-patent literature

[0003] NPL 1: Zhang et al., Applied Physics Express 12, 124003 (2019) Brief description of the invention Technical task

[0004] The nitride semiconductor element described above, such as a laser diode, can improve the injection of carriers (electrons or holes), but does not exhibit sufficiently suppressed degradation of a cladding layer.

[0005] This disclosure is based on the objective of providing a method for producing a nitride semiconductor stack and a nitride semiconductor element capable of achieving both degradation suppression of a cladding layer and an improvement in carrier injection efficiency, and of providing a nitride semiconductor element. Solution to the task

[0006] To accomplish the task described above, a method for fabricating a nitride semiconductor stack according to one aspect of the disclosure comprises: forming a first-conductivity-type cladding layer containing a first-conductivity-type nitride semiconductor on a nitride semiconductor substrate containing Al; forming a light-emitting layer using a nitride semiconductor containing one or more quantum wells on the first-conductivity-type cladding layer; forming part of a second-conductivity-type cladding layer containing a second-conductivity-type nitride semiconductor under wafer temperature conditions of 900 °C or more and 1000 °C or less, and reactor pressures of 15 mbar or more and 350 mbar or less.and forming a remaining part of the cladding layer of the second conductivity type under conditions of a wafer temperature of 1030 °C or more and 1100 °C or less and a reactor pressure of 15 mbar or more and 350 mbar or less, to form a semiconductor stack part on the nitride semiconductor substrate.

[0007] A method for producing a nitride semiconductor element according to a further aspect of the disclosure comprises: after forming the semiconductor stack part by the above-described method for producing a nitride semiconductor stack, removing an unnecessary section of the individual layers of the semiconductor stack part by etching; forming an electrode on the semiconductor stack part; and dividing the nitride semiconductor substrate on which the individual layers of the semiconductor stack part were formed into individual pieces by singulation.

[0008] A nitride semiconductor element according to another aspect of the present disclosure comprises: a nitride semiconductor substrate containing Al; and a semiconductor stack part arranged on the nitride semiconductor substrate. The semiconductor stack part has: a cladding layer of a first conductivity type containing a nitride semiconductor of a first conductivity type; a light-emitting layer arranged on the cladding layer of the first conductivity type and formed from a nitride semiconductor with one or more quantum wells; and a cladding layer of a second conductivity type arranged on the light-emitting layer and formed from a nitride semiconductor of a second conductivity type containing Al. The cladding layer of the second conductivity type has a surface with a helical stepped and terraced structure, which, in plan view, has terraces and steps that are non-linear.

[0009] It should be noted that the above summary of the invention does not list all features of the invention as disclosed. Advantageous effects of the invention

[0010] The present disclosure can provide a method for producing a nitride semiconductor stack and a nitride semiconductor element capable of achieving both degradation suppression of a cladding layer and an improvement in carrier injection efficiency, and a nitride semiconductor element. Brief description of the drawings Fig. 1 is a curve diagram showing a configuration example of the Al composition in a nitride semiconductor element according to an embodiment of the present disclosure; Fig.2A is an AFM image showing the structure of the upper surface of a cladding layer of a second conductivity type of the nitride semiconductor element according to the embodiment of the present disclosure; Fig. Figure 2B is a SEM image showing the structure of the upper surface of the cladding layer of the second conductivity type of the nitride semiconductor element according to the embodiment of the present disclosure; Fig. Figure 3 is an AFM image showing the structure of the top surface of a cladding layer of a second conductivity type of a typical nitride semiconductor element; Fig. Figure 4 is a schematic top view illustrating a configuration example of a nitride semiconductor element according to the embodiment of the present disclosure; Fig.Figure 5 is a schematic cross-sectional view illustrating a configuration example of the nitride semiconductor element according to the embodiment of the present disclosure; Fig. Figure 6 is a schematic cross-sectional view illustrating a configuration example of the nitride semiconductor element according to the embodiment of the present disclosure; and Fig. Figure 7 is a schematic cross-sectional view illustrating a configuration example of the nitride semiconductor element according to the embodiment of the present disclosure. Description of the embodiments

[0011] In the following, a nitride semiconductor element according to the present disclosure is described with reference to embodiments; however, the following embodiments do not limit the invention defined by the claims. The respective combinations of features described in the embodiments are not essential for the solution of the invention.

[0012] In the following description, "top" and "bottom" do not necessarily refer to the vertical direction relative to the ground. More precisely, the directions "top" and "bottom" are not limited to the direction of gravity. "Top" and "bottom" are merely convenient terms for indicating the relative positions of surfaces, films, substrates, and the like, and do not restrict the technical concept of the present invention. For example, it is self-evident that when the paper is rotated 180 degrees, "top" becomes "bottom" and "bottom" becomes "top." 1. First embodiment

[0013] The following is a description of a nitride semiconductor element according to a first embodiment of the present disclosure. The nitride semiconductor element according to the present embodiment is, for example, a laser diode.

[0014] The following description concerns the case where the nitride semiconductor element is a laser diode. (1.1) Configuration of the laser diode

[0015] The laser diode according to the present embodiment comprises: a nitride semiconductor substrate containing Al; and a semiconductor stack part arranged on the nitride semiconductor substrate. The semiconductor stack part has: a cladding layer of a first conductivity type, containing a nitride semiconductor of a first conductivity type; a light-emitting layer arranged on the cladding layer of the first conductivity type and formed from a nitride semiconductor with one or more quantum wells; and a cladding layer of a second conductivity type, arranged on the light-emitting layer and formed from a nitride semiconductor of a second conductivity type, containing Al. The cladding layer of the second conductivity type described above has a surface with a helical stepped and terraced structure, which, in plan view, exhibits terraces and steps that are non-linear.

[0016] A detailed description of the individual layers of the laser diode follows. <nitridhalbleitersubstrat>

[0017] The nitride semiconductor substrate (hereinafter also referred to as the "substrate") contains a nitride semiconductor containing aluminum. The aluminum-containing nitride semiconductor is, for example, AlN. In particular, the substrate is preferably an AlN single-crystal substrate. The aluminum-containing nitride semiconductor is not limited to AlN and can, for example, be AlGaN. If the substrate is, for example, a nitride semiconductor single-crystal substrate such as AlN or AlGaN, the difference in the lattice constant decreases with the formation of the nitride semiconductor layer on the top side of the substrate, and the nitride semiconductor layer grows in a lattice-matched system, thereby reducing dislocations.

[0018] The dislocation density of the substrate is preferably 5 × 10 4 cm -2 or less. In particular, from the perspective of improving the luminescence intensity and reducing an oscillation threshold current, the dislocation density is more preferably 1 × 10 3 cm -2 or more and 1 × 10 4 cm -2 or less.

[0019] The substrate can be formed on a heterosubstrate, provided it contains an aluminum nitride semiconductor. For example, AlN can be grown on a sapphire (Al₂O₃) substrate.

[0020] The term "contains" in the expression "contains a nitride semiconductor" means that a layer primarily contains a nitride semiconductor; however, this term also includes cases where another element is present. In particular, the expression also includes cases where the composition of this layer has been slightly modified, for example, by adding a small amount of an element other than the nitride semiconductor (for example, a few percent or less of an element such as Ga (if Ga is not a major element), In, As, P, or Sb). In expressions relating to the composition of the other layers, the word "contains" carries the same meaning. The small amount of elements contained is not limited to those described above.

[0021] As an example, the substrate preferably has a layer thickness of 100 µm or more and 600 µm or less. The plane orientation includes the c-plane (0001), the a-plane (11-20), the m-plane (10-10), and the like, with a substrate in the c-plane (0001) being more preferred. The substrate can, without restriction, be formed in a plane inclined at a certain angle (for example, from -4° to 4°, preferably from -0.4° to 0.4°) from the normal direction of the c-plane (0001). <pufferschicht>

[0022] A buffer layer can be formed on the substrate, specifically between the substrate and the cladding layer of the first conductivity type. The buffer layer preferably covers the entire surface of the substrate. By including the buffer layer, a nitride semiconductor layer with a small difference in lattice constant, a small difference in the coefficient of thermal expansion, and few defects is formed on the buffer layer.

[0023] The buffer layer is preferably an aluminum-containing nitride semiconductor layer and is formed, for example, from a nitride semiconductor such as AlN or AlGaN. The buffer layer may contain foreign atoms, such as carbon, silicon, iron, and magnesium.

[0024] The buffer layer has a thickness of several micrometers, for example. In particular, the thickness of the buffer layer is preferably greater than 10 nm and less than 10 µm. If the thickness of the buffer layer is greater than 10 nm, the crystallinity of the nitride semiconductor, such as AlN, increases. If the thickness of the buffer layer is less than 10 µm, cracks formed by crystal growth across the entire wafer surface are less likely to occur in the buffer layer. <Mantelschicht des ersten Leitfähigkeitstyps>

[0025] The cladding layer of the first conductivity type is formed on the substrate. The word "on" in the expression "the cladding layer of the first conductivity type is formed on the substrate" means that the cladding layer of the first conductivity type is formed on a surface of the substrate. The above expression also includes a case in which another layer is present between the substrate and the cladding layer of the first conductivity type. In the relationships between the other layers, the word "on" carries the same meaning. For example, a case in which the cladding layer of the second conductivity type is formed over an electron barrier layer described above on a waveguide layer of the first conductivity type is likewise included in the expression "the cladding layer of the second conductivity type is formed on the waveguide layer of the first conductivity type."

[0026] In the description of the present embodiment, the “first conductivity type” and the “second conductivity type” mean that the semiconductors have different types of conductivity, for example one being n-type and the other being p-type.

[0027] The cladding layer of the first conductivity type is a layer of a nitride semiconductor containing Al and Ga. For example, the cladding layer of the first conductivity type is made of Al. a Ga (1-a) N (0 < a < 1) is formed. This allows for an improvement in the crystallinity of the light-emitting layer and an improvement in the luminescence efficiency when a material with a band gap energy in the low-ultraviolet range is incorporated into the light-emitting layer. From the point of view of achieving high luminescence efficiency, the nitride semiconductor forming the cladding layer of the first conductivity type is preferably a mixed crystal of AlN and GaN. From the point of view of growing the cladding layer of the first conductivity type and the respective layers formed above the cladding layer of the first conductivity type in a continuous strand onto the substrate, the cladding layer of the first conductivity type is more preferably made of Al a Ga (1-a) N (0.65 < a ≤ 0.9) was formed.

[0028] The cladding layer of the first conductivity type can be a gradient layer, such that the Al composition increases with increasing distance from the substrate, for example, to control the conductivity in the longitudinal direction. In this case, the restriction regarding the Al composition described above can be described as the Al composition obtained by averaging the Al composition at a position in the layer thickness direction within the cladding layer of the first conductivity type with the layer thickness of the cladding layer of the first conductivity type.

[0029] If the cladding layer of the first conductivity type is an n-type semiconductor layer, it may contain impurities such as elements of group V other than N, for example P, As and Sb, C, H, F, O, Mg and Si, but the types of impurities are not limited to these. From the point of view of reducing electrical resistance and the difficulty of obtaining sources, the impurity in the cladding layer of the first conductivity type is preferably Si, and the impurity concentration is preferably 5 × 10⁻⁶. 18 cm -3 or more and 5 × 10 19 cm -3 .

[0030] The sheath layer of the first conductivity type preferably has a resistance of 1 × 10 -3 Ωcm or more and 5 × 10 -3 Ωcm or less. This allows for efficient carrier injection.

[0031] From the point of view of lattice relaxation in the cladding layer of the first conductivity type and from the point of view of the layer resistance, the cladding layer of the first conductivity type preferably has a layer thickness of 250 nm or more and 800 nm or less and more preferably a layer thickness of 300 nm or more and 450 nm or less. <Lichtemittierende Schicht>

[0032] The light-emitting layer is a layer of a nitride semiconductor containing Al and Ga. To achieve high luminescence efficiency, the nitride semiconductor in the light-emitting layer is preferably a mixed crystal, for example of AlN and GaN, and is, for example, made of Al b Ga (1-b) N (0 < b < 1) is formed. The light-emitting layer may contain foreign atoms, such as elements of group V other than N, for example P, As and Sb, C, H, F, O, Mg and Si, but the types of elements of the foreign atoms are not limited to these.

[0033] The light-emitting layer can also adopt a multiple quantum well structure or a single quantum well structure. The number of quantum well structures varies depending on the longitudinal conductivity of the cladding layer of the first conductivity type and the cladding layer of the second conductivity type, and is preferably any number from 1 to 5.

[0034] In the laser diode of the present embodiment, α, which indirectly represents potential fluctuations of the nitride semiconductor layer, is preferably 130 meV or more and 350 meV or less. The nitride semiconductor layer represented by this α can be not only the light-emitting layer, but also the waveguide layer of the first conductivity type or the waveguide layer of the second conductivity type, which will be described later. When α of the light-emitting layer, the waveguide layer of the first conductivity type, or the waveguide layer of the second conductivity type is 130 meV or more and 350 meV or less, efficient recombination of localized carriers occurs, thus improving the luminescence efficiency.

[0035] In this document, "potential fluctuations of the nitride semiconductor layer" is an index indicating the Ga distribution state in the plane direction of the nitride semiconductor layer, and "α, which indirectly represents the potential fluctuations," is an index indicating the deviation from alloy uniformity in the plane direction of the nitride semiconductor layer. When α is (approximately) 30 meV, α indicates that Ga is uniformly distributed in the plane direction of the nitride semiconductor layer, and in particular, that Al and Ga are uniformly arranged.

[0036] These potential fluctuations occur in the full width at half maximum (FWHM) of the emission spectrum of the nitride semiconductor layer. Specifically, the FWHM of the emission spectrum becomes narrower the closer the nitride semiconductor layer approaches a perfectly uniform crystal. Furthermore, the possible values ​​of the FWHM also vary depending on the aluminum composition of the nitride semiconductor. The potential fluctuations of the nitride semiconductor layer are therefore assessed using α, which represents the deviation from the FWHM of the emission spectrum in a uniform state for the respective aluminum composition. An aluminum composition x of the nitride semiconductor layer and the FWHM of the emission spectrum at the emission wavelength x can be represented by the equation FWHM (meV) = αx + 10 meV.In this context, the state at a large α is far from a uniform state, meaning that Ga and the like are isolated or spatially limited.

[0037] At the interface between a pot layer and a barrier layer in the light-emitting layer, the thickness of a region in which the Al concentration profile changes in a gradient is preferably 0.3 nm or more and 0.6 nm or less.

[0038] This can improve carrier inclusion and luminescence intensity. <wellenleiterschicht>

[0039] From the perspective of optical confinement of the laser diode, the laser diode of the present embodiment can comprise a waveguide layer formed above and below the light-emitting layer, such that it encloses the light-emitting layer and has the effect of confining the light emitted by the light-emitting layer. The waveguide layer preferably comprises two layers: a waveguide layer of the first conductivity type, arranged between the cladding layer of the first conductivity type and the light-emitting layer, and a waveguide layer of the second conductivity type, arranged between the cladding layer of the second conductivity type and the light-emitting layer.

[0040] In particular, the laser diode of the present embodiment can, for example, comprise the waveguide layer of the first conductivity type, which is arranged between the cladding layer of the first conductivity type and the light-emitting layer and encloses light in the light-emitting layer, and the waveguide layer of the second conductivity type, which is arranged between the cladding layer of the second conductivity type and the light-emitting layer and encloses light in the light-emitting layer.

[0041] From the perspective of optical confinement, the waveguide layer is preferably a nitride semiconductor containing Al, Ga with a band gap that has a higher energy than that of the light-emitting layer. The waveguide layer preferably has an Al composition and a layer thickness that enhances the superposition between the intensity distribution of the electric field of light remaining in the device and that of the light-emitting layer. From the perspective of carrier confinement in the light-emitting layer, if the light-emitting layer is Al b Ga (1-b) N (0 < b < 1) and the waveguide layer Al c Ga (1-c) N (0 < c < 1) is satisfied, preferably b < c and c ≥ b + 0.05. For example, if a light-emitting layer with an emission wavelength of 265 nm is used as an example, then b is preferably 0.52 and c is 0.57 or more.

[0042] From the point of view of optical inclusion and layer resistance, the total layer thickness of the waveguide layer (total layer thickness of the layer thickness of the waveguide layer of the first conductivity type and the layer thickness of the waveguide layer of the second conductivity type) is preferably 70 nm or more and 150 nm or less.

[0043] While the waveguide layer may contain foreign atoms, such as elements of group V other than N, for example P, As and Sb, C, H, F, O, Mg and Si, the types of foreign atoms are not limited to these. From the perspective of reducing electrical resistance and the difficulty of obtaining sources, the foreign atom in the waveguide layer of the first conductivity type is preferably Si, and the foreign atom concentration is preferably 5 × 10⁻⁶. 18 cm -3 or more and 5 × 10 19 cm -3 .

[0044] The aluminum composition of the waveguide layer of the first conductivity type and the waveguide layer of the second conductivity type is preferably uniform in the layer thickness direction without restriction. To prevent light absorption by metal located above the cladding layer of the second conductivity type described below (for example, the second electrode), the aluminum composition of the waveguide layer of the second conductivity type can be higher than that of the waveguide layer of the first conductivity type. For the same purpose, the layer thickness of the waveguide layer of the second conductivity type can be greater than that of the first waveguide. <Mantelschicht des zweiten Leitfähigkeitstyps>

[0045] The cladding layer of the second conductivity type is formed on the light-emitting layer and is a nitride semiconductor layer containing Al and Ga with conductivity of the second conductivity type. The cladding layer of the second conductivity type is, for example, made of Al d Ga (1-d) N (0.1 ≤ d ≤ 1) is formed. In particular, the cladding layer of the second conductivity type is formed on the waveguide layer of the second conductivity type. Thus, the cladding layer of the second conductivity type can easily achieve lattice matching with the light-emitting layer or the waveguide layer, and a restriction of the dislocation density is made possible.

[0046] The cladding layer of the second conductivity type is not restricted with respect to its conductivity type, as long as it has sufficient conductivity to inject carriers (electrons or holes) into the light-emitting layer and to increase the superposition between the intensity distribution of the electric field of the light mode remaining in the device and the light-emitting layer (i.e., to increase the optical confinement). The cladding layer of the second conductivity type can, for example, be p-type AlGaN doped with Mg. The cladding layer of the second conductivity type can contain foreign atoms, such as elements of group V other than N, for example P, As, and Sb, C, H, F, O, Mg, and Si, but the types of foreign atoms are not limited to these.

[0047] From the perspective of more efficient injection of carriers into the light-emitting layer, the mantle layer of the second conductivity type is a composition gradient layer made of Al d Ga (1-d) N (0,1 ≤ d ≤ 1) is formed, whose composition has such a gradient that the Al composition d as a whole becomes smaller with increasing distance from the substrate as a layer, but in a part of the mantle layer of the second conductivity type the Al composition d increases with increasing distance from the substrate.

[0048] The cladding layer of the second conductivity type preferably exhibits a composition gradient in which the Al composition d decreases in the range of 1 to 0.7 with increasing distance from the side of the nitride semiconductor substrate. The profile (gradient) of the Al composition d in the cladding layer of the second conductivity type can decrease continuously or intermittently. "Intermittent decrease" means that a portion of a layer of the cladding layer of the second conductivity type contains a section in which the Al composition d is constant (in the layer thickness direction). More precisely, the cladding layer of the second conductivity type can contain a section in which the Al composition d does not decrease in the direction away from the substrate (a section in which the Al composition d is constant or increases).

[0049] From the perspective of lattice matching, the cladding layer of the second conductivity type preferably has a thickness of 500 nm or less. From the perspective of optical inclusion, the layer thickness is more preferably 250 nm or more and 500 nm or less.

[0050] Fig. Figure 1 illustrates the Al composition (shown with the bold line) and the composition of the foreign atoms (shown with the solid line) in the individual layers of the laser diode. Fig. Figure 1 illustrates, as an example, a structure in which no buffer layer is provided.

[0051] As in Fig. As illustrated in Figure 1, the cladding layer of the second conductivity type exhibits a composition with a gradient such that the Al composition decreases with increasing distance from the substrate. A portion of the cladding layer of the second conductivity type is doped with foreign atoms, such as carbon or oxygen. A portion of the interface gradient, provided at the waveguide layer of the second conductivity type, in which the Al composition increases and the concentration profile increases discontinuously at the starting point of the composition gradient layer (interface on the side of the waveguide layer of the second conductivity type), is also doped with these foreign atoms.

[0052] Typically, the cladding layer of the second conductivity type is formed from a nitride semiconductor, which in many cases is only lightly doped to prevent diffusion of foreign atoms and improve injection efficiency. However, by enclosing a large number of foreign atoms in the portion of the cladding layer of the second conductivity type, both degradation suppression and improved injection efficiency can be achieved.

[0053] The outer layer of the second conductivity type preferably has a region in which the concentration profile of carbon or oxygen contained in the outer layer of the second conductivity type changes discontinuously at at least one location with increasing distance from the substrate. More precisely, the outer layer of the second conductivity type preferably has a region in which the concentration profile of the foreign atoms is convex in the direction of the concentration increase.Since the cladding layer of the second conductivity type has such a discontinuous region, the cladding layer of the second conductivity type has a part of the cladding layer of the second conductivity type that has an effect of suppressing the degradation of the cladding layer of the second conductivity type, while the remaining part of the cladding layer of the second conductivity type has an improvement effect for the efficiency of the injection of carriers (electrons or holes) into the light-emitting layer.In this case, the carbon or oxygen concentration profile in the cladding layer of the second conductivity type exhibits a steep gradient, which increases the efficiency of carrier injection into the light-emitting layer. The cladding layer of the second conductivity type can thus both suppress degradation and improve the efficiency of carrier injection into the light-emitting layer. Generally, the presence of a region where the concentration profile of foreign atoms is convex in one direction of concentration increase is detrimental to the efficiency of carrier injection into the light-emitting layer.Depending on the thickness of the second mantle layer, the presence of an area where the carbon or oxygen concentration profile has a steep gradient is, overall, advantageous with regard to the efficiency of injecting carriers into the light-emitting layer.

[0054] The “area in which the concentration profile changes discontinuously at at least one point with increasing distance from the substrate (nitride semiconductor substrate)” refers to an area in which the foreign atom concentration in a specific region (the foreign atom concentration measured at a measurement point within that region) differs by a factor of two or more from the surrounding foreign atom concentration (the foreign atom concentration measured at a measurement point adjacent to that region). For example, in Fig. As illustrated in Figure 1, the mantle layer of the second conductivity type has a region P in which the foreign atom concentration profile changes abruptly.

[0055] The cladding layer of the second conductivity type, as described above, has a region P in which the foreign atom concentration profile decreases discontinuously. This region P, in which the concentration profile decreases discontinuously, is preferably located in a range of 1 nm or more to 110 nm or less, and more preferably in a range of 5 nm or more to 110 nm or less, from the substrate side of the cladding layer of the second conductivity type. This prevents the degradation of the cladding layer of the second conductivity type without hindering the improvement in the efficiency of carrier injection into the light-emitting layer.

[0056] A region located on the substrate side, relative to region P of the sheath layer of the second conductivity type, where the foreign atom concentration profile decreases discontinuously, is preferably made of Al e Ga (1-e )N (0.8 ≤ e ≤ 1.0) is formed. This prevents the degradation of the cladding layer of the second conductivity type without hindering the improvement in the efficiency of injecting carriers into the light-emitting layer.

[0057] The carbon concentration in a region on the substrate side, relative to region P of the sheath layer of the second conductivity type where the foreign atom concentration profile decreases discontinuously, is more preferably 1 × 10 17 cm -3 or more and 1 × 10 18 cm -3 or less. Likewise, the oxygen concentration in a region on the substrate side, relative to region P of the sheath layer of the second conductivity type where the foreign atom concentration profile decreases discontinuously, is more preferably 1 × 10 17 cm -3 or more and 1 × 10 18 cm -3 or less. This successfully results in the formation of a layer that suppresses degradation of the cladding layer of the second conductivity type and a layer that improves the efficiency of carrier injection into the light-emitting layer. This makes it possible to successfully achieve both the effect of suppressing degradation of the cladding layer of the second conductivity type and the effect of improving the efficiency of carrier injection into the light-emitting layer in the laser diode.

[0058] As described above, the sheath layer of the second conductivity type of embodiment contains Fig. 1 Al d Ga (1-d) N (0.1 ≤ d ≤ 1) and exhibits a composition gradient in which the Al composition decreases with increasing distance from the nitride semiconductor substrate. Furthermore, at least a portion of the cladding layer of the second conductivity type is a region Q with discontinuous composition, in which the Al composition is discontinuous in the direction away from the substrate. In the region Q with discontinuous composition, the Al composition d increases with increasing distance from the substrate. Since the cladding layer of the second conductivity type includes the region Q with discontinuous composition, the laser diode can thus achieve both the effect of suppressing the degradation of the cladding layer of the second conductivity type and the effect of improving the efficiency of carrier injection into the light-emitting layer.

[0059] The region Q with discontinuous composition is preferably located in a range of 1 nm or more to 110 nm or less, and more preferably in a range of 5 nm or more to 110 nm or less, from the nitride semiconductor substrate side of the cladding layer of the second conductivity type. More precisely, the starting point of region Q with discontinuous composition preferably coincides with the starting point of region P. By enclosing region Q with discontinuous composition on the nitride semiconductor substrate side of the cladding layer of the second conductivity type, the degradation of the cladding layer of the second conductivity type can be prevented without hindering the improvement in the efficiency of carrier injection into the light-emitting layer.

[0060] The region Q with discontinuous composition preferably exhibits a composition gradient in which the Al composition d increases by 0.002 or more and by 0.05 or less with increasing distance from the substrate. Since the region Q with discontinuous composition has such a composition gradient, a layer with an effect of suppressing the degradation of the cladding layer of the second conductivity type and a layer with an effect of improving the efficiency of carrier injection into the light-emitting layer are formed. This makes it possible to achieve both the effect of suppressing the degradation of the cladding layer of the second conductivity type and the effect of improving the efficiency of carrier injection into the light-emitting layer in the laser diode even more successfully.

[0061] The sheath layer of the second conductivity type preferably contains 1 × 10 17 cm -3 or more and 5 × 10 19 cm -3 or less hydrogen at the interface on the substrate side (i.e., the interface with the waveguide layer of the second conductivity type). At least a subregion of the cladding layer of the second conductivity type contains hydrogen at a concentration higher than in other regions of the cladding layer of the second conductivity type. The cladding layer of the second conductivity type contains traces of hydrogen overall, and the cladding layer of the second conductivity type of the laser diode of the present embodiment includes a region (the subregion described above) that contains a partially high hydrogen concentration. Thus, the laser diode can compensate for point defects and achieve both the effect of suppressing the degradation of the cladding layer of the second conductivity type and the effect of improving the efficiency of carrier injection into the light-emitting layer in the laser diode.

[0062] The region where the hydrogen concentration is higher than in other regions of the cladding layer of the second conductivity type is preferably a region in the range of 1 nm or more to 110 nm or less, and more preferably a region in the range of 5 nm or more to 110 nm or less from the substrate side of the cladding layer of the second conductivity type. This makes it possible to compensate for point defects and suppress the degradation of the cladding layer of the second conductivity type without hindering the improvement in the efficiency of carrier injection into the light-emitting layer.

[0063] The full width at half maximum (FWHM) of the hydrogen concentration profile in the region where hydrogen is present in a higher concentration than in other regions of the cladding layer of the second conductivity type is preferably 5 nm or more and 10 nm or less. This makes it possible to effectively compensate for point defects and improve the efficiency of injecting carriers into the light-emitting layer.

[0064] The cladding layer of the second conductivity type can be 1 × 10 17 cm -3 or more and 5 × 10 19 cm -3 or less silicon is contained in the interface on the substrate side. At least one subregion of the cladding layer of the second conductivity type can contain silicon at a concentration higher than that of other regions of the cladding layer of the second conductivity type. The region in which the silicon concentration is higher than in other regions of the cladding layer of the second conductivity type is preferably a region in the range of 1 nm or more to 110 nm or less, and more preferably a region in the range of 5 nm or more to 110 nm or less from the substrate side of the cladding layer of the second conductivity type.

[0065] The surface of the mantle layer of the second conductivity type described above exhibits a spirally stepped and terraced structure with terraces and steps that are not linear in plan view, as shown in Fig. Figure 2A illustrates this. One example of the spiral stepped and terraced structure includes a fundamentally hexagonal shape where one of the outlines gradually becomes shorter. Other examples of the spiral stepped and terraced structure include a fundamentally circular shape where the radius gradually decreases, and a shape that is fundamentally a mixture of a hexagonal shape and straight lines where the length of the sides gradually decreases. For comparison, Figure 2A illustrates this. Fig. 3. A spirally stepped and terraced structure with terraces and steps that are linear in plan view. This makes it possible to achieve even more successfully both the effect of suppressing the degradation of the cladding layer of the second conductivity type and the effect of improving the efficiency of the injection of carriers into the light-emitting layer in the laser diode.

[0066] Such a mantle layer of the second conductivity type is formed by growth at a lower temperature than usual (described in detail later), resulting in a transition from the linear stepped and terraced structure to the spiral stepped and terraced structure. Fig. 2A is an atomic force microscopy (AFM) image illustrating the spiral stepped and terraced structure. Fig. Image 2B is a scanning electron micrograph (SEM) illustrating the circular stepped and terraced structure. A greater improvement in the luminescence efficiency of the second conductivity-type mantle layer is achieved when the helical stepped and terraced structure, rather than the circular or linear stepped and terraced structure, is formed on the surface of the second conductivity-type mantle layer. This is thought to be due to the segregation of Ga during the growth of a helical stepped and terraced structure, which increases the current injection efficiency.

[0067] The spirally shaped, stepped and terraced structure preferably has a height of 0.2 nm or more and 0.4 nm or less.

[0068] The spirally shaped, stepped and terraced structure preferably has a distribution density of 1 × 10 7 cm -2 or more and 5 × 10 8 cm -2 or less.

[0069] This achieves a significantly higher effect in suppressing the degradation of the second conductivity type cladding layer and in increasing current injection efficiency.

[0070] When a nitride semiconductor layer with a helical stepped and terraced structure is formed, and then a nitride semiconductor layer is formed using a standard procedure to create a cladding layer of the second conductivity type, the helical stepped and terraced structure also appears on the surface of the cladding layer of the second conductivity type. The helical stepped and terraced structure can be observed on the surface of the cladding layer of the second conductivity type when examining its surface shape. However, when a contact layer of the second conductivity type, as described below, is formed on the cladding layer of the second conductivity type, the helical stepped and terraced structure does not appear on the surface of the contact layer of the second conductivity type.However, if only the contact layer of the second conductivity type is removed using sulfur hexafluoride (SF6) gas or the like, in order to expose the contact layer of the second conductivity type, and the surface of the mantle layer of the second conductivity type is observed, for example by SEM or the like, the spiral stepped and terraced structure on the surface of the mantle layer of the second conductivity type can be observed. <Grenzflächengradiententeil>

[0071] The laser diode according to the present embodiment can have an interface gradient part which Al g Ga (1-g) N (0, 1 ≤ g ≤ 1) contains and in which an Al composition g increases with increasing distance from the nitride semiconductor substrate at the light-emitting layer (waveguide of the second conductivity type). The provision of the interface gradient component as in the present embodiment causes relaxation of the electric field and an improvement in the degradation suppression effect.

[0072] The interface gradient portion preferably has a layer thickness of 2 nm or more and 5 nm or less, and more preferably 2 nm or more and 3 nm or less. In this case, the degradation suppression effect is further improved. <Kontaktschicht des zweiten Leitfähigkeitstyps>

[0073] The semiconductor stack portion of the laser diode of the present embodiment can further comprise the contact layer of the second conductivity type, which is arranged on the cladding layer of the second conductivity type. The nitride semiconductor forming the contact layer of the second conductivity type is, for example, made of GaN, AlN, or InN, or a mixed crystal thereof, and preferably a GaN-containing nitride semiconductor.

[0074] In the case of a p-type contact layer, the contact layer of the second conductivity type can contain foreign atoms such as elements of group V other than N, for example P, As and Sb, C, H, F, O, Mg, Si and Be. Considering the versatility of a source gas, the foreign atom in the contact layer of the second conductivity type is preferably Mg. From the perspective of reducing the contact resistance, the Mg concentration is preferably 8 × 10⁻⁶. 19 cm -3 or more and 5 × 10 21 cm -3 or less and more preferably 5 × 10 20 cm -3 or more and 5 × 10 21 cm -3 or less.

[0075] The contact layer of the second conductivity type preferably has a thickness of 1 nm or more and 20 nm or less. Since the thickness of the contact layer of the second conductivity type is smaller, the carrier injection efficiency of the light-emitting layer is further improved. If the thickness is greater, the carrier injection efficiency decreases further. <elektronensperrschicht>

[0076] The semiconductor stack portion of the laser diode of the present embodiment can further comprise an electron barrier layer with a band gap larger than that of the light-emitting layer above the light-emitting layer. The electron barrier layer can, for example, be provided on the light-emitting layer or can also be provided within the waveguide layer of the second conductivity type, between the waveguide layer of the second conductivity type and the light-emitting layer, or between the waveguide layer of the second conductivity type and the cladding layer of the second conductivity type.

[0077] The electron barrier layer has a thickness of preferably 30 nm or less and more preferably 20 nm or less to facilitate quantum tunneling of the carriers (holes). <elektrode>

[0078] The laser diode can emit or oscillate light by injecting a current through a second electrode, located on the cladding layer of the second conductivity type, and a first electrode, located on the cladding layer of the first conductivity type. The first electrode is configured to be in electrical contact with the cladding layer of the first conductivity type, and the second electrode is configured to be in electrical contact with the cladding layer of the second conductivity type.

[0079] Regarding the first electrode, it can, for example, be located on the back side of the substrate. The first electrode is positioned on the cladding layer of the first conductivity type by removing a layer above this layer, for example, by chemical etching or dry etching. Specifically, the first electrode is positioned in a region where no mesa structure is formed in the cladding layer of the first conductivity type.

[0080] If the cladding layer of the first conductivity type 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 and Zr, mixed crystals thereof or conductive oxide such as ITO or Ga2O3.

[0081] If the cladding layer of the first conductivity type 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 and Zr, mixed crystals thereof or conductive oxide such as ITO or Ga2O3.

[0082] If the cladding layer of the second conductivity type 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 and Zr, mixed crystals thereof or conductive oxide such as ITO or Ga2O3.

[0083] If the cladding layer of the second conductivity type 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 and Zr, mixed crystals thereof or conductive oxide such as ITO or Ga2O3.

[0084] The arrangement area and shape of the first electrode and the second electrode are not restricted, as long as the respective electrical contact is achieved with the sheath layer of the first conductivity type and the sheath layer of the second conductivity type (contact layer of the second conductivity type, if the contact layer of the second conductivity type is present). (1.2) Method for producing the nitride semiconductor stack and the nitride semiconductor element

[0085] The laser diode, which is the nitride semiconductor element of the present embodiment, can be fabricated by singulating a stack of nitride semiconductors, which is produced in a single step of forming individual layers of a nitride semiconductor layer on a substrate. A method for fabricating a nitride semiconductor stack and a method for fabricating a laser diode as an example of a method for fabricating a nitride semiconductor element are described below. (1.2.1) Method for producing the nitride semiconductor stack (forming the substrate)

[0086] The substrate is formed using a standard substrate growth method, such as vapor phase growth, sublimation, hydride gas phase epitaxy (HVPE), or liquid phase growth. (Formation of the semiconductor stack layer)

[0087] The individual layers of the semiconductor stack layer formed on the substrate can be formed, for example, by molecular beam epitaxy (MBE), hydride gas phase epitaxy (HVPE), metal-organic vapor deposition (MOCVD), or the like.

[0088] Among the layers formed on the substrate, the layer of a nitride semiconductor can be formed, for example, using an Al source comprising trimethylaluminium (TMAl), a Ga source comprising trimethylgallium (TMGa) or triethylgallium (TEGa), or the like, or an N source comprising ammonia (NH3).

[0089] The semiconductor stack layer is formed on the substrate. A metal-organic gas is introduced into a chamber for the formation of the semiconductor stack layer. First, the cladding layer of the first conductivity type, which contains a nitride semiconductor of the first conductivity type, is formed on the substrate.

[0090] Then, the waveguide layer of the first conductivity type, containing a nitride semiconductor such as AlGaN, is formed on the cladding layer of the first conductivity type. Next, the light-emitting layer is formed using a nitride semiconductor (AlGaN or the like) containing one or more quantum wells. Finally, the waveguide layer of the second conductivity type, also containing a nitride semiconductor such as AlGaN, is formed on top of the light-emitting layer.

[0091] The waveguide layer of the first conductivity type, the light-emitting layer and the waveguide layer of the second conductivity type are preferably formed under conditions which, when the wafer temperature is Tw and the reactor pressure is Vw, satisfy -2Tw + 2050 < Vw < -2Tw + 2350 (850 °C < Tw < 970 °C).

[0092] This allows the formation of a light-emitting layer in which Ga is unevenly distributed in the plane direction of the nitride semiconductor layer. Similarly, a waveguide of the first conductivity type and a waveguide of the second conductivity type can be formed, in which Ga is unevenly distributed in the plane direction of the nitride semiconductor layer. This results in a localized enrichment of the carriers, which can improve the recombination rate and the luminescence efficiency.

[0093] Next, the cladding layer of the second conductivity type is formed on the waveguide layer of the second conductivity type.

[0094] Before the formation of part of the cladding layer of the second conductivity type, the inflow of the metal-organic gas is temporarily stopped to interrupt the growth of the nitride semiconductor layer, and the deposition conditions are changed.

[0095] Then, the portion of the cladding layer of the second conductivity type is preferably formed using a nitride semiconductor of a second conductivity type by changing the conditions so that 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 the inflow of the metal-organic gas is resumed.

[0096] After the formation of the cladding layer of the second conductivity type and before the formation of the remaining part of the cladding layer of the second conductivity type, the inflow of the metal-organic gas is temporarily stopped to interrupt the growth of the nitride semiconductor layer again, and the deposition conditions are changed.

[0097] Then the conditions are changed so that 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, and the inflow of the metal-organic gas is resumed, forming the remaining part of the second conductivity type of jacket layer.

[0098] By forming the cladding layer of the first conductivity type, the waveguide layer of the first conductivity type, the light-emitting layer and the waveguide layer of the second conductivity type as described above, the recombination rate of the carriers can be improved and point defects of the individual layers can be reduced, thereby improving degradation suppression and luminescence efficiency.

[0099] By setting the wafer temperature lower during the formation of part of the second conductivity-type cladding layer than during the formation of the remaining part, a region can be formed in which the carbon or oxygen concentration profile decreases discontinuously with increasing distance from the substrate in that part of the second conductivity-type cladding layer, and the remaining part of the second conductivity-type cladding layer can be formed at least at one location. In particular, the second conductivity-type cladding layer can be formed such that it contains a greater amount of carbon or oxygen than the remaining part of the second conductivity-type cladding layer. This can achieve both degradation suppression and an improvement in injection efficiency in the second conductivity-type cladding layer.

[0100] By setting the reactor pressure lower when forming part of the second conductivity type of shell than the reactor pressure when forming the remaining part of the second conductivity type of shell, the second conductivity type of shell can be formed in such a way that it contains a greater amount of carbon or oxygen, which are foreign atoms, than the remaining part of the second conductivity type of shell.

[0101] Temporarily halting the inflow of the metal-organic gas before the formation of part of the cladding layer of the second conductivity type leads to a localized enrichment of hydrogen or silicon at the interface on the substrate side of the cladding layer of the second conductivity type. Specifically, if, for example, a hydrogen gas (H2) is used as the carrier gas, the hydrogen (H) is more likely to be locally enriched in the uppermost layer of the nitride semiconductor layer, the growth of which is interrupted (for example, the interface between the waveguide layer of the second conductivity type and the cladding layer of the second conductivity type, and a portion within the cladding layer of the second conductivity type).Thus, the laser diode can further improve the effect of suppressing the degradation of the cladding layer of the second conductivity type and the effect of improving the efficiency of injecting carriers into the light-emitting layer.

[0102] When the growth of the nitride semiconductor layer is interrupted, some elements (e.g., Ga in the case of AlGaN) are typically lost, thus minimizing the growth interruption. However, by interrupting the growth and actively introducing hydrogen, and by locally enriching hydrogen at the interface between the waveguide layer of the second conductivity type and the cladding layer of the second conductivity type, and in a portion of the cladding layer of the second conductivity type, point defects of the interface are compensated, so that V III -H3 is achieved, which can improve the degradation suppression effect.

[0103] If the cladding layer of the second conductivity type is a p-type semiconductor layer, it typically does not contain silicon acting as an n-type impurity atom. However, by interrupting the growth and actively introducing silicon, and by locally enriching the silicon obtained from sources or a susceptor in the interface between the waveguide layer of the second conductivity type and the cladding layer of the second conductivity type, and in a portion of the cladding layer of the second conductivity type, point defects of the interface are compensated, thus improving the degradation suppression effect.

[0104] The region in which the carbon or oxygen concentration profile decreases discontinuously with increasing distance from the substrate in the portion of the cladding layer of the second conductivity type and in the remaining portion of the cladding layer of the second conductivity type is formed, as described above, at least at one location in the present embodiment by setting the wafer temperature lower during the formation of the portion of the cladding layer of the second conductivity type than the wafer temperature during the formation of the remaining portion of the cladding layer of the second conductivity type. However, the manufacturing process is not limited to this manufacturing process.The region in which the carbon or oxygen concentration profile decreases discontinuously with increasing distance from the substrate can also be formed, for example, by selectively changing the flow rate of the metal-organic gas during the formation of the mantle layer of the second conductivity type.

[0105] If required, an intermediate layer can be formed between the cladding layer of the second conductivity type and the waveguide layer of the second conductivity type using an AlGaN or similar nitride semiconductor, the contact layer of the second conductivity type can be provided on the cladding layer of the second conductivity type using a GaN or similar nitride semiconductor, or the electron barrier layer can be formed over the light-emitting layer. (1.2.2) Method for fabricating the nitride semiconductor element (laser diode) (forming a mesa structure)

[0106] The laser diode is fabricated in a single step of semiconductor stack formation by removing an unnecessary portion of each layer formed on the substrate through etching (mesastructure formation step). An unnecessary portion of the semiconductor stack layer can be removed, for example, by etching with inductively coupled plasma (ICP) or similar techniques.

[0107] In the mesa structure formation step, removing the unnecessary section of each layer of a conductor stack layer by etching exposes part of the cladding layer of the first conductivity type. (Formation of the electrode)

[0108] The laser diode can also be fabricated in a single step of electrode formation. The electrodes, such as the first and second electrodes, are formed by various electron beam deposition (EB) metal deposition processes, such as resistive evaporation, electron gun deposition, or sputtering, although the process is not limited to the above. The electrodes can be formed as single layers or by stacking multiple layers.

[0109] After the metal layer has formed, the electrodes can each be subjected to heat treatment in an oxygen, nitrogen or air atmosphere. (Separate)

[0110] Finally, the substrate on which the individual layers were formed by the steps described above is separated into individual pieces by singulation to produce a nitride semiconductor element (laser diode).

[0111] In particular, the first electrode is formed on the surface of the cladding layer of the first conductivity type. The second electrode is formed on the topmost layer (for example, the cladding layer of the second conductivity type) of the mesa structure formed in a portion of the semiconductor stack. The formed electrode is alloyed by heating it in a rapid thermal annealing (RTA) device, which is a heat treatment using an infrared lamp, or by laser annealing, which is a heat treatment using laser pulses, to achieve contact with the semiconductor stack. The alloying process is not particularly restricted as long as sufficient contact with the semiconductor stack is achieved.

[0112] Then the laser diode produced in the method for manufacturing a nitride semiconductor element according to the present embodiment can improve the carrier injection efficiency and increase the luminescence intensity. (1.3) Method for measuring the physical properties and the like of the laser diode

[0113] The physical properties and the like of the laser diode described above can be measured as follows. (Method for measuring layer thickness)

[0114] The layer thickness of the individual layers of the laser diode can be measured by excising a predetermined cross-section perpendicular to the substrate, viewing this cross-section with a transmission electron microscope (TEM), and using the TEM's length measurement function. The measurement procedure involves, firstly, viewing a cross-section perpendicular to the main surface of the laser diode substrate with the TEM. Specifically, the viewing width in the TEM image, which shows the cross-section perpendicular to the main surface of the laser diode substrate, is defined by a region of 2 µm or more in a direction parallel to the main surface of the substrate. Within this viewing width, a contrast is observed at the interface between two layers of different compositions, allowing the thickness to be observed up to this interface in a continuous viewing area 200 nm wide.The thickness of the individual layers can be obtained by calculating the mean thickness of the layers in this 200 nm wide viewing area at five points, which are arbitrarily extracted from the viewing width of 2 µm or more described above. (Measurement of the foreign atom concentration and the doping concentration)

[0115] The concentration of dopants or foreign atoms in the individual layers of the laser diode can be measured by secondary ion mass spectrometry (SIMS).

[0116] To measure the concentration of dopants or foreign atoms in the individual layers of the laser diode, the measurement can be performed in a state with electrodes removed by chemical etching or physical polishing, after the laser diode has been processed into a device. The concentration of dopants or foreign atoms in the individual layers can also be measured by sputtering from the substrate side where no electrodes are formed.

[0117] In particular, the SIMS measurement is performed according to the measurement conditions specified by the Evans Analytical Group (EAG). A cesium (Cs) ion beam with an energy of 14.5 keV is used to sputter a sample during the measurement. (Method for measuring the atomic concentration of individual layers)

[0118] One method for measuring the concentration of atoms in the individual layers of the laser diode involves reciprocal space mapping (RSM) using X-ray diffraction (XRD). Specifically, the lattice relaxation rate to a basis and the Al composition can be analyzed by examining reciprocal lattice map data near the diffraction peak, which is obtained using an asymmetric plane as the diffraction plane. Examples of diffraction planes include the (10-15) and (20-24) planes.

[0119] Layers or areas for which sufficient reflectance cannot be obtained using XRD, such as the light-emitting layer, the gradient layer and elevations formed in the individual layers, can be measured using X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDX) and electron energy-loss spectroscopy (EELS).

[0120] In EELS, the composition of a sample is analyzed by measuring the energy lost when the electron beam passes through the sample. Specifically, the energy loss spectrum of the transmitted electron beam intensity is measured and analyzed in a thin sample, such as one used for TEM observation. The composition can then be determined from the peak position, exploiting the fact that the peak position, which appears around the energy loss magnitude of 20 eV, changes depending on the composition of the respective layer.

[0121] In the same way as in the method for calculating the layer thickness using the TEM analysis described above, the Al composition of the individual layers is obtained by calculating the mean value of the Al composition in the observation width of 200 nm at five locations arbitrarily extracted from the observation area of ​​2 µm or more.

[0122] In EDX, for example, a characteristic X-ray beam generated by the electron beam in the thin sample used for TEM observation is measured and analyzed. In the same way as in the method for calculating the layer thickness using the TEM observation described above, the Al composition of the individual layers is obtained by calculating the average Al composition at five arbitrarily selected locations within a 200 nm viewing width, taken from the 2 µm or larger viewing area.

[0123] In XPS, the depth-directed evaluation is performed by conducting an XPS measurement during sputter etching using an ion beam. Ar+ is generally used for the ion beam, although other ion species, such as Ar cluster ions, are acceptable as long as they are ions that can be emitted by an ion gun mounted in the XPS device. The distribution of the Al composition in the depth direction of the individual layers is obtained by measuring and analyzing the XPS peak intensity of Al, Ga, and N. Alternatively, instead of sputter etching, the laser diode can be polished obliquely, such that a cross-section perpendicular to the main surface of the substrate is exposed in a magnified manner, and this exposed cross-section is then measured using XPS.

[0124] The composition of the individual layers can be determined using Auger electron spectroscopy (AES) and XPS. In this case, the composition can be measured using Auger electron spectroscopy on the cross-section exposed by sputter etching or oblique polishing. The composition of the individual layers can also be measured by SEM-EDX on the cross-section exposed by sputter etching or oblique polishing. (Method for measuring potential fluctuations)

[0125] α, which indirectly indicates potential fluctuations, is calculated using the equation FWHM (meV) - αx + 10 meV, taking into account the Al composition x of the nitride semiconductor layer and the full width at half maximum (FWHM) at the emission wavelength. Specifically, FWHM is determined from the emission spectrum obtained by applying a photoluminescence measurement to the nitride semiconductor layer. α can be obtained using the Al composition x of the nitride semiconductor layer. The photoluminescence measurement uses a light source with a wavelength shorter than the band gap of the nitride semiconductor layer being excited. A 213 nm YAG laser with frequency tripling is used as an example. More accurate values ​​can be obtained by measuring a sample cooled to 10 K or less.If a layer with a smaller band gap than that of the nitride semiconductor layer to be excited is present, a specific layer can be measured by removing the layer through etching or similar methods. In particular, if the light-emitting layer is present on the waveguide layer of the first conductivity type, the quantized light-emitting layer will be excited by excitation light, so that correct values ​​can be obtained by removing the light-emitting layer by etching and subsequently measuring the waveguide layer of the first conductivity type. (Method for measuring surface shape)

[0126] Methods for measuring the surface shape of the cladding layer of the second conductivity type include scanning electron microscopy (SEM) and atomic force microscopy (AFM).

[0127] In particular, the surface of the cladding layer of the second conductivity type is examined at an accelerating voltage of 30 kV using a Hitachi High-Tech SU9000 scanning electron microscope. The surface shape of the cladding layer of the second conductivity type can be clearly seen by setting a magnification of 10,000x to 50,000x. Under these conditions, the number of spiral-shaped, stepped, and terraced structures in the field of view is measured, and a value obtained by dividing the number by the area is used as the density of the spiral-shaped, stepped, and terraced structure.

[0128] The step height of the spirally stepped and terraced surface structure of the mantle layer of the second conductivity type can be measured using AFM. Specifically, the observation is carried out using a Hitachi High-Tech scanning probe microscope. In AFM mode, a 2 µm square area is examined with the scanning probe microscope. The step height can then be determined from the resulting AFM image. (Areas of application of the nitride semiconductor element)

[0129] The laser diode according to the present disclosure is applicable, for example, to devices in the field of medicine and life sciences, in the environmental field, in the industrial field, in the field of everyday and household appliances, in the agricultural field and in other fields.The laser diode is applicable to synthesis and decomposition devices for chemicals or chemical substances, sterilization devices for liquids, gases and solids (containers, food, medical devices and the like), cleaning devices for semiconductors and the like, surface modification devices for films, glass and metal, exposure devices for semiconductor manufacturing, flat panel displays (FPDs), printed circuit boards (PCBs) and other electronic products, printing and coating devices, bonding and sealing devices, transfer and forming devices for films, samples, dummies and the like, and measuring and testing devices for banknotes, scratches, blood, chemical substances and the like.

[0130] Examples of liquid sterilizers include, but are not limited to, automatic ice makers and ice compartments and water supply tanks for ice storage containers and ice makers in refrigerators, freezers, ice machines, humidifiers, dehumidifiers, cold water tanks, hot water tanks and flow pipes for water dispensers, stationary water purifiers, portable water purifiers, water heating devices, wastewater treatment devices, disposal devices, toilet drain plugs, washing machines, dialysis water disinfection modules, plug-in disinfectors for peritoneal dialysis and disaster water storage systems.

[0131] Examples of gas sterilizers include, but are not limited to, air purifiers, air conditioners, ceiling fans, floor or bed vacuums, futon dryers, shoe dryers, washing machines, clothes dryers, home sterilization lamps, warehouse ventilation systems, shoe cabinets and wardrobes.

[0132] Examples of solid sterilizers (including surface sterilizers) include, but are not limited to, vacuum packaging machines, conveyor belts, tool sterilizers for medical, dental, hairdressing and beauty salon use, toothbrushes, toothbrush cases, chopstick cases, cosmetic bags, drain covers, bidets and toilet lids. 2. Second embodiment

[0133] The following is a description of a nitride semiconductor element according to a second embodiment of the present disclosure. The nitride semiconductor element according to the present embodiment is, for example, a light-emitting element.

[0134] The following description concerns the case where the nitride semiconductor element is a light-emitting element. (2.1) Configuration of the light-emitting element

[0135] The light-emitting element according to the present embodiment comprises: a nitride semiconductor substrate containing Al; and a semiconductor stack part arranged on the nitride semiconductor substrate. The semiconductor stack part has: a cladding layer of a first conductivity type containing a nitride semiconductor of a first conductivity type; a light-emitting layer arranged on the cladding layer of the first conductivity type and formed from a nitride semiconductor with one or more quantum wells; and a cladding layer of a second conductivity type arranged on the light-emitting layer and formed from a nitride semiconductor of a second conductivity type containing Al. The cladding layer of the second conductivity type has a surface with a helical stepped and terraced structure, which, in plan view, exhibits terraces and steps that are non-linear.

[0136] The light-emitting element of the present embodiment differs from the laser diode of the first embodiment in that the light-emitting element does not include a waveguide layer of the first conductivity type and a waveguide layer of the second conductivity type. In the light-emitting element according to the present embodiment, the cladding layer of the second conductivity type is sometimes used as a barrier layer.

[0137] The light-emitting element of the present embodiment has a different configuration than the cladding layer of the first conductivity type of the laser diode of the first embodiment. Therefore, the cladding layer of the first conductivity type and the cladding layer of the second conductivity type of the light-emitting element are described in detail below.

[0138] Layers other than the cladding layer of the first conductivity type, namely the nitride semiconductor substrate, the buffer layer and the light-emitting layer, are similar to the layers described in the first embodiment, which is why their description is omitted. <Mantelschicht des ersten Leitfähigkeitstyps>

[0139] The cladding layer of the first conductivity type is a layer of a nitride semiconductor containing Al and Ga. For example, the cladding layer of the first conductivity type is made of Al. a Ga( 1-a )N (0 < a < 1) and preferably, for example, made of Al a Ga( 1-a )N (0,7 ≤ a ≤ 1) formed.

[0140] The cladding layer of the first conductivity type is preferably formed from an n-type semiconductor.

[0141] The cladding layer of the first conductivity type preferably has a layer thickness T0 of 3300 × a - 2100 nm or more and 15700 × a - 10100 nm or less (where a is the proportion of Al atoms if the totality of atoms of group III of the nitride semiconductor 1 forming the cladding layer of the first conductivity type).

[0142] The sheath layer of the first conductivity type preferably has a resistance of 1 × 10 -3 Ωcm or more and 5 × 10 -3 Ωcm or less.

[0143] The remaining configurations are the same as the configurations of the sheath layer of the first conductivity type described in the first embodiment. <Mantelschicht des zweiten Leitfähigkeitstyps>

[0144] In the light-emitting element, an electron barrier layer with a constant aluminum composition is provided not on the cladding layer of the second conductivity type with a graded aluminum composition, but rather on the light-emitting layer itself, and the contact layer of the second conductivity type with a graded aluminum composition is provided on the electron barrier layer. The electron barrier layer and the contact layer of the second conductivity type with a graded aluminum composition function as a cladding layer.

[0145] By growing the electron barrier layer at a lower temperature than usual, it is possible, as with the laser diode of the first embodiment, to achieve an effect of suppressing the degradation of the electron barrier layer and the contact layer of the second conductivity type, and an effect of improving the efficiency of carrier injection into the light-emitting layer. If the electron barrier layer and the contact layer of the second conductivity type are considered as the cladding layer of the second conductivity type, the inflow of the metal-organic gas is temporarily stopped before the electron barrier layer is grown in order to interrupt the growth of the nitride semiconductor layer, and only a portion of the electron barrier layer is grown at the lower temperature.As with the cladding layer of the second conductivity type of the laser diode, a light-emitting element is obtained in which the carbon or oxygen concentration profile decreases discontinuously, hydrogen is locally enriched in the interface on the side of the light-emitting layer of the electron barrier layer, and the electron barrier layer contains a larger quantity of foreign atoms than usual.

[0146] After the growth of the electron barrier layer and before the growth of the contact layer of the second conductivity type, the inflow of the metal-organic gas is temporarily stopped to interrupt the growth of the nitride semiconductor layer, whereby an area away from the nitride semiconductor substrate side of the cladding layer of the second conductivity type (layer obtained by combining the electron barrier layer and the contact layer of the second conductivity type), corresponding to the thickness of the electron barrier layer, may contain hydrogen in a higher concentration than in other areas.

[0147] The electron barrier layer preferably has a thickness of 10 nm or more and 15 nm or less. In particular, the light-emitting element has a region in which the concentration profile of carbon or oxygen in the electron barrier layer decreases discontinuously, preferably in a range of 10 nm or more to 15 nm or less starting from the substrate side of the electron barrier layer.

[0148] Unlike the laser diode according to the first embodiment, the light-emitting element according to the present embodiment does not contain the waveguide layer of the first conductivity type or the waveguide layer of the second conductivity type. This makes it more difficult to determine α, which indirectly represents potential fluctuations. If an attempt is made to determine α, which indirectly represents potential fluctuations, the quantized light-emitting layer is excited, so that incorrect results are not obtained. However, forming the nitride semiconductor layer under the same conditions as in the first embodiment makes it possible to form a nitride semiconductor layer with the same α, which indirectly represents potential fluctuations. 3. Specific examples of the nitride semiconductor element

[0149] In the following, the nitride semiconductor element of the present embodiment is described with reference to Fig. 4 to Fig. Section 7 is described in more detail. The detailed configuration of the individual layers in the following examples is as described above. (3.1) First example

[0150] Fig. Figure 4 is a schematic cross-sectional view of a laser diode 1 as a first example. As in Fig. As shown in Figure 4, the laser diode 1 comprises a substrate 11, a semiconductor stack part 10 arranged on the substrate, a first electrode 13 and a second electrode 14. The semiconductor stack part 10 comprises a cladding layer 101 of the first conductivity type, whose conductivity type is n-type, a waveguide layer 102 of the first conductivity type, a light-emitting layer 103, a waveguide layer 104 of the second conductivity type and a cladding layer 105 of the second conductivity type, whose conductivity type is p-type. (3.2) Second example

[0151] Fig. Figure 5 is a schematic cross-sectional view of a laser diode 2 as a second example. As in Fig. As shown in Figure 5, the laser diode 2 comprises the substrate 11, a buffer layer 12, the semiconductor stack part 10, which is arranged on the substrate 11 (buffer layer 12), the first electrode 13 and the second electrode 14. The semiconductor stack part 10 comprises the cladding layer 101 of the first conductivity type, whose conductivity type is n-type, the waveguide layer 102 of the first conductivity type, the light-emitting layer 103, the waveguide layer 104 of the second conductivity type and the cladding layer 105 of the second conductivity type, whose conductivity type is p-type.

[0152] In particular, laser diode 2 differs from laser diode 1 in that the buffer layer 12 is present. (3.3) Third example

[0153] Fig. Figure 6 is a schematic cross-sectional view of a laser diode 3 as a third example. As in Fig. As shown in Figure 6, the laser diode 3 comprises the substrate 11, the buffer layer 12, the semiconductor stack part 10 formed on the substrate, the first electrode 13, and the second electrode 14. The semiconductor stack part 10 comprises the cladding layer 101 of the first conductivity type, whose conductivity type is n-type, the waveguide layer 102 of the first conductivity type, the light-emitting layer 103, the waveguide layer 104 of the second conductivity type, the cladding layer 105 of the second conductivity type, whose conductivity type is p-type, and a contact layer 106.

[0154] In particular, the laser diode differs from the laser diode 1 in that it includes the contact layer 106.

[0155] The laser diode of the present disclosure can be configured to include the buffer layer 12 described in the second example and the contact layer 106 described in the third example. (3.4) Fourth example

[0156] Fig. Figure 7 is a schematic cross-sectional view of a light-emitting element 4 as a first example. As in Fig. As shown in Figure 7, the light-emitting element 4 comprises the substrate 11, the semiconductor stack part 10 arranged on the substrate, the first electrode 13, and the second electrode 14. The semiconductor stack part 10 comprises the cladding layer 101 of the first conductivity type, which is n-type, the light-emitting layer 103, and the cladding layer 105 of the second conductivity type, which is p-type. Within the light-emitting element 4, the electron barrier layer and the contact layer of the second conductivity type are provided to function as the cladding layer 105 of the second conductivity type.

[0157] In particular, the light-emitting element 4 differs from the laser diode 1 in that the waveguide layer 102 of the first conductivity type and the waveguide layer 104 of the second conductivity type are not present. The light-emitting element 4 differs from the laser diode 1 in that the electron barrier layer and the contact layer of the second conductivity type are provided to function as the cladding layer 105 of the second conductivity type.

[0158] The light-emitting element can be configured to include the buffer layer 12 described in the second example. 4. Effects

[0159] The nitride semiconductor element described above exhibits the following effects.

[0160] The nitride semiconductor element of the present disclosure comprises: the nitride semiconductor substrate containing Al; and the semiconductor stack part arranged on the nitride semiconductor substrate. The semiconductor stack part includes: the cladding layer of the first conductivity type, containing a nitride semiconductor of the first conductivity type; the light-emitting layer, arranged on the cladding layer of the first conductivity type and formed from a nitride semiconductor with one or more quantum wells; and the cladding layer of the second conductivity type, arranged on the light-emitting layer and formed from a nitride semiconductor of the second conductivity type, containing Al. The cladding layer of the second conductivity type has a surface with a helical stepped and terraced structure, which, in plan view, exhibits terraces and steps that are non-linear.

[0161] This makes it possible to achieve both the degradation prevention effect of the cladding layer of the second conductivity type and the effect of improving the efficiency of the injection of carriers into the light-emitting layer in the laser diode.

[0162] (2) In the nitride semiconductor element of the present disclosure, the spiral stepped and terraced structure preferably has a height of 0.2 nm or more and 0.4 nm or less.

[0163] This further improves the current injection efficiency and achieves a significantly higher degradation prevention effect of the cladding layer of the second conductivity type.

[0164] (3) In the nitride semiconductor element of the present disclosure, the spiral stepped and terraced structure preferably has a distribution density of 1 × 10 7 cm -2 or more and 5 × 10 8 cm -2 or less.

[0165] This further improves the current injection efficiency and achieves a significantly higher degradation prevention effect of the cladding layer of the second conductivity type.

[0166] (4) The process for fabricating a nitride semiconductor stack of the present disclosure comprises: forming the first conductivity-type cladding layer, containing a first conductivity-type nitride semiconductor, on the nitride semiconductor substrate containing Al; forming the light-emitting layer using a nitride semiconductor containing one or more quantum wells, on the first conductivity-type cladding layer; forming the portion of the second conductivity-type cladding layer, containing a second conductivity-type nitride semiconductor, under conditions of a wafer temperature of 900 °C or more and 1000 °C or less and a reactor pressure of 15 mbar or more and 350 mbar or less;and forming the remaining part of the cladding layer of the second conductivity type under conditions of a wafer temperature of 1030 °C or more and 1100 °C or less and a reactor pressure of 15 mbar or more and 350 mbar or less, to form the semiconductor stack part on the nitride semiconductor substrate.

[0167] In this way, the part of the mantle layer of the second conductivity type can be formed in such a way that it contains a larger amount of carbon or oxygen than the rest of the mantle layer of the second conductivity type, and both degradation suppression and improvement of injection efficiency into the mantle layer of the second conductivity type can be achieved.

[0168] (5) In the process for producing a nitride semiconductor stack of the present disclosure, the reactor pressure during the formation of part of the cladding layer of the second conductivity type is preferably 15 mbar or more and 100 mbar or less.

[0169] In this way, the part of the mantle layer of the second conductivity type can be formed in such a way that it contains a larger amount of carbon or oxygen than the rest of the mantle layer of the second conductivity type, and both the degradation suppression effect and the improvement of the injection efficiency into the mantle layer of the second conductivity type can be achieved.

[0170] (6) The method for producing a nitride semiconductor stack of the present disclosure preferably comprises: introducing a metal-organic gas during the formation of the cladding layer of the first conductivity type, the light-emitting layer and the cladding layer of the second conductivity type; temporarily stopping the inflow of the metal-organic gas after the formation of the light-emitting layer and before the formation of part of the cladding layer of the second conductivity type; and temporarily stopping the inflow of the metal-organic gas after the formation of part of the cladding layer of the second conductivity type and before the formation of the remaining part of the cladding layer of the second conductivity type.

[0171] This allows the growth of the layer containing the nitride semiconductor to be temporarily interrupted, and hydrogen or silicon to be locally enriched at the interface on the substrate side of the second conductivity type cladding layer, and the effect of suppressing the degradation of the second conductivity type cladding layer and improving the efficiency of carrier injection into the light-emitting layer can be further enhanced. EXAMPLES<Probe 1>

[0172] The laser diode of the present disclosure is described below with reference to examples and comparative examples. The laser diode of the present disclosure is not limited to these examples.

[0173] A (0001)-plane AlN single crystal substrate with a thickness of 550 µm was used as the substrate.

[0174] Next, a homoepitaxial AlN layer was formed on the substrate. The AlN layer was 500 nm thick and formed at 1200 °C. The V / III ratio (the ratio between a source gas of element group III and a nitrogen source gas) was set to 50. The AlN layer grew at a rate of 0.5 µm / h. Trimethylaluminium (TMAl) was used as the aluminum source, and ammonia (NH3) as the nitrogen source.

[0175] A sheath layer of the first conductivity type was formed on this substrate. For the sheath layer of the first conductivity type, an n-type AlGaN layer (Al: 75%, i.e., an Al 0,75 Ga 0,25 The first conductivity type of molten layer was formed to a thickness of 400 nm under conditions of a temperature of 1050 °C, a reactor pressure set to 50 mbar, and a V / III ratio of 4000. The growth rate of the first conductivity type of molten layer was 0.4 µm / h. Trimethylaluminium (TMAl) was used as the aluminum source. Triethylgallium (TEGa) was used as the gallium source. Ammonia (NH3) was used as the nitrogen source. Monosilane (SiH4) was used as the silicon source.

[0176] Then, an n-type waveguide layer, which was a first waveguide layer, was formed on the cladding layer of the first conductivity type. For the n-type waveguide layer, an n-type AlGaN layer (Al: 63%, i.e., an Al 0,63 Ga 0,37 An n-type waveguide layer containing silicon as a dopant was used. The n-type waveguide layer was formed to a thickness of 40 nm under conditions of a temperature of 950 °C, a reactor pressure set to 300 mbar, and a V / III ratio of 4000. The growth rate of the n-type waveguide layer was 0.35 µm / h.

[0177] Trimethylaluminium (TMAl) was used as the aluminum source. Triethylgallium (TEGa) was used as the gallium source. Ammonia (NH3) was used as the nitrogen source.

[0178] Then, a light-emitting layer was formed on the n-type waveguide layer. This light-emitting layer was created by forming a layer with a multiple quantum well structure, in which a quantum well layer and a barrier layer were stacked on top of each other in two periods. The quantum well layer was an AlGaN layer (Al: 52%, i.e., an Al 0,52 Ga 0,48 N-layer), with a thickness of 4.5 nm, was used. For the barrier layer with a thickness of 6.0 nm, an AlGaN layer (Al: 63%, i.e., an Al 0,63 Ga 0,37 N-layer) , used.

[0179] The light-emitting layer was formed under conditions of a temperature of 950 °C, a reactor pressure set to 300 mbar, and a V / III ratio of 4000. The growth rate of the quantum well layer was 0.18 µm / h. The growth rate of the barrier layer was 0.15 µm / h.

[0180] Then a second waveguide layer, a p-type waveguide layer, was formed on the light-emitting layer. For the p-type waveguide layer, an AlGaN layer without dopants (Al: 63%, i.e., an Al 0,63 Ga 0,37 The p-type waveguide layer was formed to a thickness of 70 nm under conditions of a temperature of 950 °C, a reactor pressure set to 300 mbar, and a V / III ratio of 4000. The growth rate of the p-type waveguide layer was 0.35 µm / h. Trimethylaluminum (TMAl) was used as the aluminum source, and triethylgallium (TEGa) as the gallium source.

[0181] A cladding layer of a second conductivity type was then formed on the p-type waveguide layer. This second conductivity cladding layer is a composition gradient layer with a graded aluminum composition. For this second conductivity cladding layer, an AlGaN layer with a thickness of 2.5 nm was used, in which the aluminum composition exhibited a distribution away from the substrate and the aluminum content changed from 0.63 to 1.0 (interface gradient portion). A p-type AlGaN layer with a thickness of 330 nm was also used, in which the aluminum composition exhibited a distribution away from the substrate and the aluminum content changed from 1.0 to 0.7.

[0182] Prior to the growth of the second conductivity-type cladding layer, the reactor pressure was set to 50 mbar at a temperature of 950°C, with the inflow of the metal-organic gas temporarily stopped and only hydrogen and NH3 being emitted. A layer (A) with an initial thickness of 72.5 nm and an Al composition corresponding to 0.63 → 1.0 → 0.95 (the layer formed from the interfacial gradient portion and the portion of the second conductivity-type cladding layer) was formed under a V / III ratio of 4000. The growth rate was 0.3 to 0.5 µm / h.Layer (A) is formed from the interface gradient portion and the portion of the cladding layer of the second conductivity type. Within layer (A), which has a thickness of 72.5 nm, a region with a thickness of 2.5 nm, where the Al composition is 0.63 → 1.0, is the "interface gradient portion," and the remaining region, with a thickness of 70 nm, where the Al composition is 1.0 → 0.95, is the "part of the cladding layer of the second conductivity type." The "interface gradient portion" is thus a region contained within the cladding layer of the second conductivity type.

[0183] Next, the reactor pressure was adjusted to 50 mbar at a temperature of 1050 °C, with the inflow of the metal-organic gas temporarily stopped and only hydrogen and NH3 being emitted. A layer (B) with a remaining thickness of 257.5 nm and an Al composition corresponding to 0.98 → 0.7 (the remaining part of the cladding layer formed by the second conductivity type) was formed under a V / III ratio of 4000. The growth rate was 0.3 to 0.5 µm / h.

[0184] Throughout the preceding step, trimethylaluminium (TMAl) was used as the Al source and triethylgallium (TEGa) as the Ga source. The interface between the layers (A) and (B) described above corresponds to region P, where the impurity concentration profile changes abruptly, or to region Q with discontinuous composition, where the Al composition is discontinuous in the direction away from the substrate.

[0185] Then, a p-type contact layer, representing the contact layer of the second conductivity type, was formed on the cladding layer of the second conductivity type. This p-type contact layer consisted of an AlGaN layer and a GaN layer. The AlGaN layer was a p-type nitride semiconductor layer with a thickness of 30 nm, containing Mg as a dopant, with an Al composition oriented away from the substrate and varying from 0.7 to 0.4. The GaN layer was formed from GaN with a thickness of 10 nm (i.e., Al: 0%).

[0186] The contact layer of the second conductivity type was formed under conditions of a temperature of 950 °C, a reactor pressure set to 150 mbar, and a V / III ratio of 3650. The growth rate of the contact layer of the second conductivity type was 0.2 µm / h.

[0187] The nitride semiconductor stack obtained as described above was subjected to various analyses. These revealed that the region with the graded Al composition at the interface between the pot layer and the barrier layer in the light-emitting layer was 0.5 nm. α, which indirectly indicates the potential fluctuations, was 146 meV.

[0188] Then, a discontinuity point in the Al composition was observed at the interface between the mantle layers (A) and (B) of the second conductivity type, and the initial composition of (B) was 3% higher than that of (A). At the interface between (A) and (B), 5 × 10 18 cm -3 Hydrogen and 5 × 10 18 cm -3 Si observed. The FWHM of the hydrogen peak was 7.5 nm. A greater amount of oxygen and carbon was also detected in (A) than in (B), and the concentration profile changed discontinuously at the interface between (A) and (B). The oxygen and carbon concentrations were each 3 × 10 17 cm -3 and 3 × 10 17 cm -3 .

[0189] As a result of removing the contact layer of the second conductivity type with SF6 gas and examining the surface, the surface shape exhibited a spirally stepped and terraced structure with a fundamentally hexagonal shape, in which the step height was 0.3 nm and the step density was 5 × 10 7 cm -2 fraud.

[0190] Curing the semiconductor stack formed as described above in an N2 atmosphere at 700 °C for 10 minutes or more further reduced the resistance of the contact layer of the second conductivity type. Dry etching with a Cl2-containing gas using ICP created a mesa structure in which the cladding layer of the first conductivity type was exposed.

[0191] The resulting mesa structure had a length of 700 µm in the <1-100> direction and a length of 40 µm in the <11-20> direction. The length in the <1-100> direction of the mesa structure is the distance between the resonator mirror end faces in plan view, and the length in the <11-20> direction is the distance between the side faces of the mesa structure.

[0192] At the contact layer of the second conductivity type in the mesa structure, Ni and Au were successively deposited into rectangular layers elongated in the <1-100> direction to form multiple electrode metal regions, thus yielding p-type second electrodes. The second electrode had a width of 5 µm and a length of 600 µm or more. In the region where the n-type cladding layer in the mesa structure was exposed, V, Al, Ni, Ti, and Au were successively deposited into rectangular layers elongated in the <1-100> direction to form multiple electrode metal regions, thus yielding n-type first electrodes. The first and second electrodes were cured using an RTA device at 550 °C for 60 seconds in a nitrogen atmosphere.

[0193] Furthermore, the substrate was divided into strips by repeatedly cleaving parallel to the <11-20> direction in the electrode metal regions, thereby forming isolated laser diodes. After division, the length in the <1-100> direction of the mesa structure was 600 µm.

[0194] When the laser diodes obtained as described above were subjected to a current end-surface luminescence measurement by current injection, the threshold voltage was 8 V and the oscillation threshold current was 3 kA / cm². 2 The oscillation time was 100 seconds. <Probe 2> until<Probe 4>

[0195] Laser diodes from sample 2 to sample 4 were formed in the same way as sample 1, except that the Al composition of the n-conducting AlGaN layer was changed, which contained Si as the dopant foreign atoms, forming the cladding layer of the first conductivity type, as shown in Table 1. <Probe 5>until<Probe 8>

[0196] Laser diodes from sample 5 to sample 8 were formed in the same way as sample 1, except that the layer thickness of the cladding layer of the first conductivity type was changed as shown in Table 1. <Probe 9> until<Probe 25>

[0197] Laser diodes from sample 10 to sample 28 were formed in the same manner as sample 1, except that the wafer temperature and reactor pressure were varied during the growth of the nitride semiconductor layer during the formation of the light-emitting layer, the first conductivity-type waveguide, and the second conductivity-type waveguide layer, as shown in Table 1. The growth temperature and pressure given in the fields for the light-emitting layer in Table 1 are the temperatures during the formation of the light-emitting layer, the first waveguide layer, and the second waveguide layer. α, which here indirectly represents the potential fluctuations of the first waveguide layer, had the value shown in Table 1. <Probe 26> until<Probe 29>

[0198] Laser diodes from sample 26 to sample 29 were formed in the same manner as sample 1, except that the wafer temperature was changed during the growth of the nitride semiconductor layer while forming the cladding layer of the second conductivity type, as shown in Tables 1 and 2. The degree of discontinuity at the discontinuity point of the Al composition and the concentration of carbon or oxygen in the cladding layer of the second conductivity type were the values ​​shown in Table 1.Examination of the surface of the individual samples showed that a spiral stepped terrace with a basically circular shape had formed in sample 26, a stepped terrace with a partially angled circular shape had formed in sample 27, a spiral stepped and terraced structure with a basically mixed hexagonal shape and straight lines could be observed in sample 28, and a linear stepped and terraced structure could be observed in sample 29. <Probe 30> until<Probe 32>

[0199] Laser diodes from sample 30 to sample 32 were formed in the same manner as sample 1, except that the reactor pressure was changed during the growth of the nitride semiconductor layer while forming part of the substrate-side cladding layer of the second conductivity type, as shown in Tables 1 and 2. The degree of discontinuity at the discontinuity point of the Al composition and the concentration of carbon or oxygen in the cladding layer of the second conductivity type were the values ​​shown in Table 2. <Probe 33> until<Probe 35>

[0200] Laser diodes from sample 33 to sample 35 were formed in the same manner as sample 1, except that the wafer temperature was changed during the growth of the nitride semiconductor layer while forming the remaining part of the cladding layer of the second conductivity type, 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 cladding layer of the second conductivity type were the values ​​shown in Table 2. <Probe 36> until<Probe 38>

[0201] Laser diodes from sample 36 to sample 38 were formed in the same manner as sample 1, except that the reactor pressure was changed during the growth of the nitride semiconductor layer while forming the remaining part of the cladding layer of the second conductivity type, 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 cladding layer of the second conductivity type were the values ​​shown in Table 2. <Probe 39> until<Probe 42>

[0202] Laser diodes from sample 39 to sample 42 were fabricated in the same manner as sample 1, except that the thickness of the remaining portion of the cladding layer of the second conductivity type and the total thickness of the cladding layer of the second conductivity type were modified 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 cladding layer of the second conductivity type were the values ​​shown in Table 2. <Probe 43> until<Probe 44>

[0203] Laser diodes from sample 43 to sample 44 were formed in the same way as sample 1, except that the thickness of the composition gradient layer formed between the waveguide layer of the second conductivity type and the cladding layer of the second conductivity type was changed as shown in Table 2. <Probe 45> until<Probe 49>

[0204] Laser diodes from sample 45 to sample 49 were fabricated in the same manner as sample 1, except that the thickness of a region where the Al composition of a portion on the substrate side of the cladding layer of the second conductivity type decreases was changed to 30 nm, 5 nm, 2 nm, 110 nm, and 150 nm, respectively, and the thickness of the remaining portion of the cladding layer of the second conductivity type was changed so that the total thickness of the cladding layer of the second conductivity type was 330 nm. The thickness of the portion on the substrate side of the cladding layer of the second conductivity type is defined as the distance from the substrate side to a region where the Al composition becomes discontinuous or the carbon or oxygen concentration profile decreases discontinuously. <Probe 50> until<Probe 53>

[0205] Laser diodes from sample 50 to sample 53 were formed in the same way as sample 1, except that the hydrogen concentration of a part on the substrate side of the cladding layer of the second conductivity type was changed by varying the growth interruption time. <Probe 54> until<Probe 55>

[0206] Laser diodes from sample 54 to sample 55 were formed in the same way as sample 1, except that no growth interruption of the nitride semiconductor layer was performed before and after the formation of the part on the substrate side of the cladding layer of the second conductivity type. <Probe 56>

[0207] A laser diode of sample 56 was formed in the same way as sample 1, except that the cladding layer of the second conductivity type was formed in such a way that there was no discontinuity point of the Al composition in the interface of a part on the substrate side and a remaining part of the cladding layer of the second conductivity type, by continuously supplying a predetermined amount of Ga during growth interruption. [Table 1] Sheath layer of the first conductivity type Light-emitting layer Waveguide layer of the second conductivity type Sheath layer of the second conductivity type Al composition Layer thickness (nm) Wake-up temperature Tw (°C) Growth pressure Vw (mbar) Interface slope (nm) Fluctuation (meV) part of the mantle layer Remaining part of the mantle layer Interface gradient part Layer thickness (nm) Growth temperature (°C) Growth pressure (mbar) Growth temperature (°C) Growth pressure (mbar) Thickness (nm) Sample 1 0,75 400 950 300 0,5 146 950 50 1050 50 2,5 330,0 Sample 2 0,7 400 950 300 0,5 146 950 50 1050 50 2,5 330,0 Sample 3 0,65 400 950 300 0,5 146 950 50 1050 50 2,5 330,0 Sample 4 0,9 400 950 300 0,5 146 950 50 1050 50 2,5 330,0 Sample 5 0,75 250 950 300 0,5 146 950 50 1050 50 2,5 330,0 Sample 6 0,75 200 950 300 0,5 146 950 50 1050 50 2,5 330,0 Sample 7 0,75 850 950 300 0,5 146 950 50 1050 50 2,5 330,0 Sample 8 0,75 900 950 300 0,5 146 950 50 1050 50 2,5 330,0 Sample 9 0,75 400 970 200 0,6 133 950 50 1050 50 2,5 330,0 Sample 10 0,75 400 970 300 0,6 139 950 50 1050 50 2,5 330,0 Sample 11 0,75 400 970 100 0,6 126 950 50 1050 50 2,5 330,0 Sample 12 0,75 400 970 500 0,6 125 950 50 1050 50 2,5 330,0 Sample 13 0,75 400 950 200 0,5 155 950 50 1050 50 2,5 330,0 Sample 14 0,75 400 950 400 0,5 140 950 50 1050 50 2,5 330,0 Sample 15 0,75 400 950 500 0,5 200 950 50 1050 50 2,5 330,0 Sample 16 0,75 400 950 100 0,5 180 950 50 1050 50 2,5 330,0 Sample 17 0,75 400 900 200 0,4 190 950 50 1050 50 2,5 330,0 Sample 18 0,75 400 900 300 0,4 240 950 50 1050 50 2,5 330,0 Sample 19 0,75 400 900 400 0,4 255 950 50 1050 50 2,5 330,0 Sample 20 0,75 400 900 500 0,4 235 950 50 1050 50 2,5 330,0 Sample 21 0,75 400 900 600 0,4 210 950 50 1050 50 2,5 330,0 Sample 22 0,75 400 850 300 0,3 270 950 50 1050 50 2,5 330,0 Sample 23 0,75 400 850 400 0,3 330 950 50 1050 50 2,5 330,0 Sample 24 0,75 400 850 550 0,3 300 950 50 1050 50 2,5 330,0 Sample 25 0,75 400 850 700 0,3 260 950 50 1050 50 2,5 330,0 Sample 26 0,75 400 950 300 0,5 146 900 50 1050 50 2,5 330,0 Sample 27 0,75 400 950 300 0,5 146 850 50 1050 50 2,5 330,0 Sheath layer of the second conductivity type Growth interruption Discontinuity point of the Al composition Hydrogen concentration (cm³) -3 ) Half-width hydrogen (nm) Discontinuity point of C and O concentration surface Degree of discontinuity (%) Layer thickness range (nm) Present on the substrate side Layer thickness range (nm) Oxygen concentration (cm³) -3 ) Carbon concentration (cm³) -3 ) form Height (nm) Density (cm³) -2 ) Interrupted Available 3,0 72,5 5,0 × 1018 7,5 Available 72,5 3,0 × 1017 3,0 × 1017 spiral 0,3 1 × 10 8 Interrupted Available 3,0 72,5 5,0 × 1018 7,5 Available 72,5 3,0 × 1017 3,0 × 1017 spiral 0,3 1 × 10 8 Interrupted Available 3,0 72,5 5,0 × 1018 7,5 Available 72,5 3,0 × 1017 3,0 × 1017 spiral 0,3 1 × 10 8 Interrupted Available 3,0 72,5 5,0 × 10 18 7,5 Available 72,5 3,0 × 10 17 3,0 × 10 17 spiral 0,3 1 × 10 8 Interrupted Available 3,0 72,5 5,0 × 10 18 7,5 Available 72,5 3,0 × 10 17 3,0 × 10 17 spiral 0,3 1 × 10 8 Interrupted Available 3,0 72,5 5,0 × 10 18 7,5 Available 72,5 3,0 × 10 17 3,0 × 10 17 spiral 0,3 1 × 10 8 Interrupted Available 3,0 72,5 5,0 × 10 18 7,5 Available 72,5 3,0 × 10 17 3,0 × 10 17 spiral 0,3 1 × 10 8 Interrupted Available 3,0 72,5 5,0 × 10 18 7,5 Available 72,5 3,0 × 10 17 3,0 × 10 17 spiral 0,3 1 × 10 8 Interrupted Available 3,0 72,5 5,0 × 10 18 7,5 Available 72,5 3,0 × 10 17 3,0 × 10 17 spiral 0,3 1 × 10 8 Interrupted Available 3,0 72,5 5,0 × 10 18 7,5 Available 72,5 3,0 × 10 17 3,0 × 10 17 spiral 0,3 1 × 10 8 Interrupted Available 3,0 72,5 5,0 × 10 18 7,5 Available 72,5 3,0 × 10 17 3,0 × 10 17 spiral 0,3 1 × 10 8 Interrupted Available 3,0 72,5 5,0 × 10 18 7,5 Available 72,5 3,0 × 10 17 3,0 × 10 17 spiral 0,3 1 × 10 8 Interrupted Available 3,0 72,5 5,0 × 10 18 7,5 Available 72,5 3,0 × 10 17 3,0 × 10 17 spiral 0,3 1 × 10 8 Interrupted Available 3,0 72,5 5,0 × 10 18 7,5 Available 72,5 3,0 × 10 17 3,0 × 10 17 spiral 0,3 1 × 10 8 Interrupted Available 3,0 72,5 5,0 × 10 18 7,5 Available 72,5 3,0 × 10 17 3,0 × 10 17 spiral 0,3 1 × 10 8 Interrupted Available 3,0 72,5 5,0 × 10 18 7,5 Available 72,5 3,0 × 10 17 3,0 × 10 17 spiral 0,3 1 × 10 8 Interrupted Available 3,0 72,5 5,0 × 10 18 7,5 Available 72,5 3,0 × 10 17 3,0 × 10 17 spiral 0,3 1 × 10 8 Interrupted Available 3,0 72,5 5,0 × 10 18 7,5 Available 72,5 3,0 × 10 17 3,0 × 10 17 spiral 0,3 1 × 10 8 Interrupted Available 3,0 72,5 5,0 × 10 18 7,5 Available 72,5 3,0 × 10 17 3,0 × 10 17 spiral 0,3 1 × 10 8 Interrupted Available 3,0 72,5 5,0 × 10 18 7,5 Available 72,5 3,0 × 10 17 3,0 × 10 17 spiral 0,3 1 × 10 8 Interrupted Available 3,0 72,5 5,0 × 10 18 7,5 Available 72,5 3,0 × 10 17 3,0 × 10 17 spiral 0,3 1 × 10 8 Interrupted Available 3,0 72,5 5,0 × 10 18 7,5 Available 72,5 3,0 × 10 17 3,0 × 10 17 spiral 0,3 1 × 10 8 Interrupted Available 3,0 72,5 5,0 × 10 18 7,5 Available 72,5 3,0 × 10 17 3,0 × 10 17 spiral 0,3 1 × 10 8 Interrupted Available 3,0 72,5 5,0 × 10 18 7,5 Available 72,5 3,0 × 10 17 3,0 × 10 17 spiral 0,3 1 × 10 8 Interrupted Available 3,0 72,5 5,0 × 10 18 7,5 Available 72,5 3,0 × 10 17 3,0 × 10 17 spiral 0,3 1 × 10 8 Interrupted Available 3,0 72,5 5,0 × 10 18 7,5 Available 72,5 1,0 × 10 18 1,0 × 10 18 Circular spiral 0,6 6 × 10 7 Interrupted Available 3,0 72,5 5,0 × 10 18 7,5 Available 72,5 3,0 × 10 18 3,0 × 10 18 Circular 0,6 1 × 10 7 Characteristic values ​​of the light-emitting element Threshold voltage (V) Oscillation threshold (kA / cm²) 2 ) Oscillation time(s) 8 3 100 7 3,3 100 7 8 20 9,5 4 30 10 3 35 13 3 20 6,5 6 90 6,5 8 50 8,1 3,6 90 8,1 3,3 95 8,1 9 20 8,1 6 35 8 5,5 73 8 2,8 98 8 5,5 65 8 6,5 55 8 7 45 8,2 3,6 78 8,2 3 95 8,2 3,3 90 8,2 6,5 40 8,3 7 34 8,3 4 77 8,3 3,2 80 8,3 6 30 10 4 100 12 5 22 [Table 2] Sheath layer of the first conductivity type Light-emitting layer Waveguide layer of the second conductivity type Sheath layer of the second conductivity type Al composition Layer thickness (nm) Wake-up temperature Tw (°C) Growth pressure Vw (mbar) Interface steepness (nm) Fluctuation (meV) part of the mantle layer Remaining part of the mantle layer Interface gradient part Layer thickness (nm) Growth temperature (°C) Growth pressure (mbar) Growth temperature (°C) Growth pressure (mbar) Thickness (nm) Sample 28 0,75 400 950 300 0,5 146 1000 50 1050 50 2,5 330,0 Sample 29 0,75 400 950 300 0,5 146 1030 50 1050 50 2,5 330,0 Sample 30 0,75 400 950 300 0,5 146 950 15 1050 50 2,5 330,0 Sample 31 0,75 400 950 300 0,5 146 950 100 1050 50 2,5 330,0 Probe32 0,75 400 950 300 0,5 146 950 150 1050 50 2,5 330,0 Sample 33 0,75 400 950 300 0,5 146 950 50 1030 50 2,5 330,0 Sample 34 0,75 400 950 300 0,5 146 950 50 1000 50 2,5 330,0 Sample 35 0,75 400 950 300 0,5 146 950 50 1100 50 2,5 330,0 Probe36 0,75 400 950 300 0,5 146 950 50 1050 15 2,5 330,0 Sample 37 0,75 400 950 300 0,5 146 950 50 1050 100 2,5 330,0 Sample 38 0,75 400 950 300 0,5 146 950 50 1050 150 2,5 330,0 Sample 39 0,75 400 950 300 0,5 146 950 50 1050 50 2,5 250,0 Probe40 0,75 400 950 300 0,5 146 950 50 1050 50 2,5 200,0 Probe41 0,75 400 950 300 0,5 146 950 50 1050 50 2,5 400,0 Probe42 0,75 400 950 300 0,5 146 950 50 1050 50 2,5 450,0 Sample 43 0,75 400 950 300 0,5 146 950 50 1050 50 2,0 330,0 Sample 44 0,75 400 950 300 0,5 146 950 50 1050 50 5,0 330,0 Sample 45 0,75 400 950 300 0,5 146 950 50 1050 50 2,5 330,0 Sample 46 0,75 400 950 300 0,5 146 950 50 1050 50 2,5 330,0 Probe47 0,75 400 950 300 0,5 146 950 50 1050 50 2,5 330,0 Sample 48 0,75 400 950 300 0,5 146 950 50 1050 50 2,5 330,0 Sample 49 0,75 400 950 300 0,5 146 950 50 1050 50 2,5 330,0 Sample 50 0,75 400 950 300 0,5 146 950 50 1050 50 2,5 330,0 Probe51 0,75 400 950 300 0,5 146 950 50 1050 50 2,5 330,0 Probe52 0,75 400 950 300 0,5 146 950 50 1050 50 2,5 330,0 Sample 53 0,75 400 950 300 0,5 146 950 50 1050 50 2,5 330,0 Sample 54 0,75 400 950 300 0,5 146 950 50 1050 50 2,5 330,0 Sample 55 0,75 400 950 300 0,5 146 950 50 1050 50 2,5 330,0 Sample 56 0,75 400 950 300 0,5 146 950 50 1050 50 2,5 330,0 Sheath layer of the second conductivity type Growth interruption Discontinuity point of the Al composition Hydrogen concentration (cm³) -3 ) Half-width hydrogen (nm) Discontinuity point of C and O concentration surface Degree of discontinuity (%) Layer thickness range (nm) Present on the substrate side Layer thickness range (nm) Oxygen concentration (cm³) -3 ) Carbon concentration (cm³) -3 ) form Height (nm) Density (cm²) Interrupted Available 2,0 72,5 5,0 × 10 18 7,5 Available 72,5 1,0 × 10 17 1,0 × 10 17 Hexagonal / straight line spiral - - Interrupted Available 1,0 72,5 5,0 × 10 18 7,5 Available 72,5 5,0 × 10 16 5,0 × 10 16 Straight line - - Interrupted Available 3,0 72,5 5,0 × 10 18 7,5 Available 72,5 5,0 × 10 17 5,0 × 10 17 spiral 0,3 6 ×10 7 Interrupted Available 3,0 72,5 5,0 × 10 18 7,5 Available 72,5 2,0 × 10 17 2,0 × 10 17 spiral 0,3 2 ×10 8 Interrupted Available 3,0 72,5 5,0 × 10 18 7,5 Available 72,5 1,0 × 10 17 1,0 × 10 17 spiral 0,3 4 ×10 8 Interrupted Available 0,2 72,5 5,0 × 10 18 7,5 Available 72,5 3,0 × 10 17 3,0 × 10 17 spiral 0,3 4 ×10 8 Interrupted Available 0,0 72,5 5,0 × 10 18 7,5 Available 72,5 3,0 × 10 17 3,0 × 10 17 spiral 0,3 4 ×10 8 Interrupted Available 5,0 72,5 5,0 × 10 18 7,5 Available 72,5 3,0 × 10 17 3,0 × 10 17 spiral 0,3 4 ×10 8 Interrupted Available 3,0 72,5 5,0 × 10 18 7,5 Available 72,5 3,0 × 10 17 3,0 × 10 17 spiral 0,3 1 ×10 8 Interrupted Available 3,0 72,5 5,0 × 10 18 7,5 Available 72,5 3,0 × 10 17 3,0 × 10 17 spiral 0,3 1 ×10 8 Interrupted Available 3,0 72,5 5,0 × 10 18 7,5 Available 72,5 3,0 × 10 17 3,0 × 10 17 spiral 0,3 1 ×10 8 Interrupted Available 3,0 72,5 5,0 × 10 18 7,5 Available 72,5 3,0 × 10 17 3,0 × 10 17 spiral 0,3 1 ×10 8 Interrupted Available 3,0 72,5 5,0 × 10 18 7,5 Available 72,5 3,0 × 10 17 3,0 × 10 17 spiral 0,3 1 ×10 8 Interrupted Available 3,0 72,5 5,0 × 10 18 7,5 Available 72,5 3,0 × 10 17 3,0 × 10 17 spiral 0,3 1 ×10 8 Interrupted Available 3,0 72,5 5,0 × 10 18 7,5 Available 72,5 3,0 × 10 17 3,0 × 10 17 spiral 0,3 1 ×10 8 Interrupted Available 3,0 72,5 5,0 × 10 18 7,5 Available 72,5 3,0 × 10 17 3,0 × 10 17 spiral 0,3 1 ×10 8 Interrupted Available 3,0 72,5 5,0 × 10 18 7,5 Available 72,5 3,0 × 10 17 3,0 × 10 17 spiral 0,3 1 ×10 8 Interrupted Available 3,0 32,5 5,0 × 10 18 7,5 Available 32,5 3,0 × 10 17 3,0 × 10 17 spiral 0,3 1 ×10 8 Interrupted Available 3,0 7,5 5,0 × 10 18 7,5 Available 5 3,0 × 10 17 3,0 × 10 17 spiral 0,3 1 ×10 8 Interrupted Available 3,0 4,5 5,0 × 10 18 7,5 Available 4,5 3,0 × 10 17 3,0 × 10 17 spiral 0,3 1 ×10 8 Interrupted Available 3,0 112,5 5,0 × 10 18 7,5 Available 112,5 3,0 × 10 17 3,0 × 10 17 spiral 0,3 1 ×10 8 Interrupted Available 3,0 152,5 5,0 × 10 18 7,5 Available 152,5 3,0 × 10 17 3,0 × 10 17 spiral 0,3 1 ×10 8 Interrupted Available 3,0 72,5 1,0 × 10 17 7,5 Available 72,5 3,0 × 10 17 3,0 × 10 17 spiral 0,3 1 ×10 8 Interrupted Available 3,0 72,5 5,0 × 10 18 4,0 Available 72,5 3,0 × 10 17 3,0 × 10 17 spiral 0,3 1 ×10 8 Interrupted Available 3,0 72,5 1,0 x 10 19 7,5 Available 72,5 3,0 × 10 17 3,0 × 10 17 spiral 0,3 1 ×10 8 Interrupted Available 3,0 72,5 1,0 × 10 20 12,0 Available 72,5 3,0 × 1017 3,0 × 10 17 spiral 0,3 1 ×10 8 Uninterrupted Available 3,0 72,5 1,0 x 10 15 7,5 Available 72,5 3,0 × 1017 3,0 × 10 17 spiral 0,3 1 ×10 8 Uninterrupted Available 3,0 72,5 5,0 × 10 18 7,5 Unavailable - 5,0 × 1016 5,0 × 1016 spiral 0,3 1 ×10 8 Interrupted Unavailable 3,0 72,5 5,0 × 10 18 7,5 Available 72,5 3,0 × 1017 3,0 × 10 17 spiral 0,3 1 ×10 8 Characteristic values ​​of the light-emitting element Threshold voltage (V) Oscillation threshold (kA / cm²) 2 ) Oscillation time(s) 8 5 100 7,7 8 30 8,2 4 15 8 3 95 7,8 7 65 8,5 3,9 75 9,9 3,3 55 9,2 4,5 70 9 3,4 70 8,3 4 80 8,5 44 70 7,5 5,5 80 7,3 12 45 9 3,3 75 11 3 30 8,2 3,3 90 8,5 3,5 65 7,9 5 80 7,8 4,5 85 7,8 6 65 9,3 5 75 12 9 3 8 3 90 8 3 10 8 3 85 8 3 12 8 3 10 11 6 12 11 5 23

[0208] Of samples 1 to 56 in Tables 1 and 2, it was observed that the laser diodes which had undergone growth interruption of the nitride semiconductor layer before and after the formation of the substrate-side portion of the second conductivity-type cladding layer, and which comprised a second conductivity-type cladding layer with a surface formed to exhibit a helical stepped and terraced structure with non-linear terraces and steps, showed an overall reduced threshold voltage and oscillation threshold and an increased oscillation time compared to those laser diodes of samples 27 and 29 that did not have such a helical stepped and terraced structure. This confirmed that both cladding layer degradation inhibition and carrier injection efficiency improvement were achieved.

[0209] The above descriptions include embodiments of the present disclosure, but these embodiments are merely examples of devices and methods for implementing the technical concept of the present disclosure. The technical concept of the present disclosure does not specify the materials, shapes, structures, arrangements, and the like of the components described below. The technical concept of the present disclosure can be modified in various ways within the scope defined by the claims. List of reference symbols 1, 2, 3 Laser diode 4 light-emitting elements 10 Semiconductor stack part 11 Substrat 12 Buffer layer 13 first electrode 14 second electrode 101 Sheath layer of the first conductivity type 102 Waveguide layer of the first conductivity type 103 light-emitting layer 104 Waveguide layer of the second conductivity type 105 Sheath layer of the second conductivity type 106 Contact layer QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited non-patent literature

[0000] Zhang et al., Applied Physics Express 12, 124003 (2019

[0003] < / elektrode> < / elektronensperrschicht> < / wellenleiterschicht> < / pufferschicht> < / nitridhalbleitersubstrat>

Claims

[1] Method for producing a stack of nitride semiconductors, comprising: Forming a first conductivity-type cladding layer containing a first conductivity-type nitride semiconductor on a nitride semiconductor substrate containing Al; Forming a light-emitting layer using a nitride semiconductor containing one or more quantum wells on the cladding layer of the first conductivity type; Forming part of a cladding layer of a second conductivity type containing a nitride semiconductor of a second conductivity type, under conditions of a wafer temperature of 900 °C or more and 1000 °C or less and a reactor pressure of 15 mbar or more and 350 mbar or less; and Forming a remaining part of the cladding layer of the second conductivity type under conditions of a wafer temperature of 1030 °C or more and 1100 °C or less and a reactor pressure of 15 mbar or more and 350 mbar or less to form a semiconductor stack part on the nitride semiconductor substrate. [2] Method for producing a nitride semiconductor stack according to claim 1, wherein the reactor pressure during the formation of the part of the cladding layer of the second conductivity type is 15 mbar or more and 100 mbar or less. [3] Method for producing a nitride semiconductor stack according to claim 1 or 2, comprising: Inflow of a metal-organic gas during the formation of the first conductivity type cladding layer, the light-emitting layer, and the second conductivity type cladding layer; After the formation of the light-emitting layer and before the formation of part of the cladding layer of the second conductivity type, the inflow of the metal-organic gas is temporarily stopped; and After the formation of part of the shell layer of the second conductivity type and before the formation of the remaining part of the shell layer of the second conductivity type, the inflow of the metal-organic gas is temporarily stopped. [4] Method for producing a nitride semiconductor element, comprising: after forming the semiconductor stack part by the method for producing a nitride semiconductor stack according to one of claims 1 to 3 Removing an unnecessary section of the individual layers of the semiconductor stack part by etching; Forming an electrode on the semiconductor stack part; and Dividing the nitride semiconductor substrate, on which the individual layers of the semiconductor stack part were formed, into individual pieces by singulation. [5] Nitride semiconductor element comprising: a nitride semiconductor substrate containing Al; and a semiconductor stack component arranged on the nitride semiconductor substrate, wherein the semiconductor stack part has: a cladding layer of a first conductivity type containing a nitride semiconductor of a first conductivity type; a light-emitting layer arranged on the cladding layer of the first conductivity type and formed from a nitride semiconductor containing one or more quantum wells; and a cladding layer of a second conductivity type, arranged on the light-emitting layer and formed from a nitride semiconductor of a second conductivity type containing Al, and The mantle layer of the second conductivity type has a surface with a spiral stepped and terraced structure, which in plan view has terraces and steps rather than a linear one. [6] Nitride semiconductor element according to claim 5, wherein the spiral stepped and terraced structure has a height of 0.2 nm or more and 0.4 nm or less. [7] Nitride semiconductor element according to claim 5, wherein the spiral stepped and terraced structure has a distribution density of 1 × 10 7 cm -2 or more and 5 × 10 8 cm -2 or less. [8] Nitride semiconductor element according to claim 5, wherein the nitride semiconductor substrate is an AlN single crystal substrate. [9] Nitride semiconductor element according to claim 5, wherein the cladding layer of the first conductivity type is made of Al a Ga( 1-a )N (0.65 < a ≤ 0.9) is formed. [10] Nitride semiconductor element according to claim 5, wherein the cladding layer of the first conductivity type has a thickness of 250 nm or more and 800 nm or less. [11] Nitride semiconductor element according to claim 5, comprising: a first-type conductivity waveguide layer positioned between the first-type conductivity cladding layer and the light-emitting layer, and configured to trap light within the light-emitting layer; and a waveguide layer of a second conductivity type, positioned between the cladding layer of the second conductivity type and the light-emitting layer, and configured to trap light in the light-emitting layer. [12] Nitride semiconductor element according to claim 5, comprising: a contact layer of a second conductivity type, arranged on the cladding layer of the second conductivity type and formed from a nitride semiconductor containing GaN, wherein the sheath layer of the second conductivity type Al d Ga( 1-d )N (0,1 ≤ d ≤ 1) contains and has a composition gradient in which an Al composition becomes smaller with increasing distance from the nitride semiconductor substrate, and has a layer thickness of 500 nm or less. [13] Nitride semiconductor element according to claim 12, wherein the cladding layer of the second conductivity type has a composition gradient in which the Al composition d decreases in a range of 1 to 0.7 with increasing distance from one side of the nitride semiconductor substrate. [14] Nitride semiconductor element according to claim 12 or 9, wherein the cladding layer of the second conductivity type has a layer thickness of 250 nm or more and 400 nm or less. [15] Nitride semiconductor element according to claim 5, wherein the cladding layer of the first conductivity type has a layer thickness T0 of 3300 × a - 2100 nm or more and 15700 × a - 10100 nm or less (where a is the proportion of Al atoms if the totality of the atoms of group III of the nitride semiconductor 1 forming the cladding layer of the first conductivity type). [16] Nitride semiconductor element according to claim 15, wherein the cladding layer of the first conductivity type has a resistance of 1 × 10 -3 Ωcm or more and 5 × 10 -3 Ωcm or less.

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