JP2020047635A - Nitride semiconductor laser diode - Google Patents

Abstract

To provide a nitride semiconductor laser diode capable of improving the yield and extending a service life.SOLUTION: A laser diode 1 includes a base 12 provided on a substrate 11, a first semiconductor layer 311 provided on a part of the upper surface of the substrate 12, and a light emitting unit 32 provided on a part of the upper surface of the first semiconductor layer 311, and the substrate 12 includes a region where the first semiconductor layer 311 is not formed, which is an upper region 121 having the upper surface 12a formed of AlGaN (x1+y1=1, 0≤x1<1, 0<y1≤1).SELECTED DRAWING: Figure 1

Description

  The present invention relates to a nitride semiconductor laser diode.

  There are various types of nitride semiconductor laser diodes depending on the structure, and one of them is a Fabry-Perot nitride semiconductor laser diode using a cleavage plane of a crystal as a reflection mirror. As a method of exposing the cleavage plane, there are generally two types of a method of cutting along a cleavage plane of a crystal and a method of using an etching technique. A method using an etching technique is generally used because it can be applied even when the cleavage plane of the nitride semiconductor on the substrate is different from that of the substrate and has high versatility.

  Patent Document 1 discloses that a sapphire substrate is exposed by removing a group III nitride semiconductor by performing an etching method combining dry etching and wet etching on a structure in which a group III nitride semiconductor is stacked on a sapphire substrate. A method and a structure for forming a laser diode having a resonator surface on the side surface of a group III nitride semiconductor are disclosed.

JP-A-10-41585

  The laser diode having the structure disclosed in Patent Literature 1 has a problem that the yield of a cleaning process at the time of assembling the laser diode is reduced and a problem of shortening the life of the laser diode occurs.

  An object of the present invention is to provide a nitride semiconductor laser diode capable of improving the yield and extending the life.

In order to achieve the above object, a nitride semiconductor laser diode according to one embodiment of the present invention includes a base provided on a substrate, a first semiconductor layer provided on a part of an upper surface of the base, A light-emitting portion provided on a part of the upper surface of the semiconductor layer, wherein the base is a region where the first semiconductor layer is not formed, and wherein Al _x1 Ga _y1 N (x1 + y1 = 1, 0 ≦ x1 < 1, 0 <y1 ≦ 1), and has an upper region including the upper surface.

  According to one embodiment of the present invention, yield can be improved and life can be increased.

1 is a perspective view schematically showing an example of a structure of a nitride semiconductor laser diode according to one embodiment of the present invention. FIG. 2 is a view for explaining a nitride semiconductor laser diode according to an embodiment of the present invention, and shows a tetramethylammonium hydroxide aqueous solution (25) with respect to an Al composition ratio of AlGaN forming an upper surface of a base provided in the nitride semiconductor laser diode. %) Is a correlation graph of the etching amount of the AlGaN when immersed at 85 ° C. for 5 minutes. FIG. 2 is a view for explaining a nitride semiconductor laser diode according to Example 1 of one embodiment of the present invention, which shows a nitride semiconductor laser diode when immersed in a tetramethylammonium hydroxide aqueous solution (25%) at 85 ° C. for 5 minutes. It is a SEM image of a section. FIG. 3 is a diagram illustrating a nitride semiconductor laser diode according to one embodiment of the present invention, in which the nitride semiconductor laser diode according to Comparative Example 1 is immersed in a tetramethylammonium hydroxide aqueous solution (25%) at 85 ° C. for 15 minutes. It is a SEM image of a section. FIG. 3 is a diagram illustrating a nitride semiconductor laser diode according to one embodiment of the present invention, in which a nitride semiconductor laser diode according to Comparative Example 2 is immersed in a tetramethylammonium hydroxide aqueous solution (25%) at 85 ° C. for 30 minutes. It is a SEM image of a section.

  As a result of the present inventors' earnest studies on the causes of the reduction in the yield of the cleaning process at the time of assembling the laser diode having the structure disclosed in Patent Document 1 and the problem of shortening the life of the laser diode, the present inventors have found that the structure is It has been found that the laser diode of the above has poor chemical resistance and moisture resistance, and particularly under a basic environment, the dissolution and corrosion of the nitride semiconductor are severely invaded. Then, the present inventors have reached the invention of the following nitride semiconductor laser diode based on this finding.

  A nitride semiconductor laser diode according to one embodiment of the present invention will be described with reference to FIGS. First, an example of the structure of the nitride semiconductor laser diode (hereinafter abbreviated as “laser diode”) 1 according to the present embodiment will be described with reference to FIG.

  As shown in FIG. 1, the laser diode 1 according to the present embodiment includes a substrate 11, a base 12 provided on the substrate 11, a first semiconductor layer 311 provided on a part of the upper surface 12a of the base 12, And a mesa semiconductor layer 312 provided on a part of the first semiconductor layer 311. The laser diode 1 includes a lower guide layer 321 provided on the mesa semiconductor layer 312, a light emitting layer 322 provided on the lower guide layer 321, and an upper guide layer 323 provided on the light emitting layer 322. ing. The laser diode 1 includes a second semiconductor layer 331 provided on the upper guide layer 323, and a ridge portion semiconductor layer 332 provided on the second semiconductor layer 331. The laser diode 1 includes a first electrode 14 provided on the first semiconductor portion 31 and a second electrode 15 provided on the ridge portion semiconductor layer 332.

  The lower guide layer 321, the light emitting layer 322, and the upper guide layer 323 together form the light emitting section 32. The second semiconductor portion 33 is configured by combining the second semiconductor layer 331 and the ridge portion semiconductor layer 332. The first semiconductor layer 311 is arranged on a part of the upper surface 12 a of the base 12. Therefore, on the upper surface 12a of the base 12, there are a region where the first semiconductor layer 311 is not formed and a region where the first semiconductor layer 311 is formed. The first semiconductor layer 31 is configured by combining the first semiconductor layer 311 and the mesa semiconductor layer 312. The first semiconductor section 31, the light emitting section 32, and the second semiconductor section 33 together constitute the nitride semiconductor element section 13.

The laser diode 1 includes a resonator surface 16 provided on a side surface in a direction in which light including at least the side surfaces of the first semiconductor layer 311 and the light emitting unit 4 is emitted to the outside. More specifically, the resonator surface 16 is formed by the same plane formed by the side surface of the first semiconductor unit 31, the side surface of the light emitting unit 32, and the side surface of the second semiconductor unit 33. Cavity surface 16 _is formed by _{Al x2 Ga y2 N (x2 +} y2 = 1,0 ≦ x2 ≦ 0.8,0.2 ≦ y2 ≦ 1). The resonator surface 16 is composed of a plurality of layers of a first semiconductor unit 31, a light emitting unit 32, and a second semiconductor unit 33, and each of the first semiconductor unit 31, the light emitting unit 32, and the second semiconductor unit 33 has side _is formed by _{Al x2 Ga y2 N (x2 +} y2 = 1,0 ≦ x2 ≦ 0.8,0.2 ≦ y2 ≦ 1).

The base 12 of the laser diode 1 is a region where the first semiconductor layer 311 is not formed, and is the upper surface formed of Al _x1 Gay ₁ N (x1 + y1 = 1, 0 ≦ x1 <1, 0 <y1 ≦ 1). . Is provided. In addition, the laser diode 1 may include an insulating layer covering the exposed surfaces of the nitride semiconductor element portion 13 and the base 12. Examples of the insulating layer include, but are not limited to, oxides and nitrides such as SiN, SiO _2, SiON, Al ₂ O ₃ , and ZrO layers. By coating the insulating layer, the durability of the laser diode 1 can be improved, and a long-life laser diode 1 can be realized.

  Next, the details of each component constituting the laser diode 1 will be described with reference to FIG.

(substrate)
Specific examples of the material for forming the substrate 11 include Si, SiC, MgO, Ga ₂ O ₃ , Al ₂ O ₃ , ZnO, GaN, InN, AlN, and mixed crystals thereof. When a substrate formed of GaN and a nitride semiconductor such as AlN and AlGaN is used among these materials, the nitride semiconductor having a small difference in lattice constant and thermal expansion coefficient between the substrate 11 and the base 12 and having few defects Layers can be grown. Furthermore, when an AlN substrate is also used, the base 12 can be grown under compressive stress, and the occurrence of cracks in the base 12 can be suppressed. Further, impurities may be mixed in the material forming the substrate 11.

  The substrate 11 preferably has a thin rectangular shape in terms of assembly, but is not limited to this.

(base)
The material forming the base 12 is AlN, GaN, and a mixed crystal thereof. That is, the base 12 may include AlN. Examples _{AlN, Al x Ga (1-} x) N (0 ≦ x <1) can be mentioned. In addition, these materials may contain a group V element other than N such as P, As, and Sb, and impurities such as C, H, F, O, Mg, and Si. At least the upper surface 12a of the upper region 121 of the base 12 is formed of AlGaN in a region where the first semiconductor layer 311 is not formed. The base portion 12 may contain, for example, B or In other than Al and Ga as the group III element, but the formation of defects and a change in durability occur at locations containing B and In. It preferably does not contain a group III element. The base 12 may have conductivity or may be an insulator. When the base 12 is an n-type semiconductor, the base 12 is made n-type by, for example, doping Si (for example, 1 × 10 ¹⁹ cm ⁻³ ). When the base 12 is made of a p-type semiconductor, the base 12 is made p-type by, for example, doping Mg (for example, 3 × 10 ¹⁹ cm ⁻³ ).

The base 12 may have a single-layer structure or a laminated structure. Base 12, and AlN layer provided on the example substrate 11 as a laminated structure, may have a stacked structure of _Al x Ga _y N layer provided between the AlN layer (0 ≦ x <1) Good. The base portion 12 has, for example, an Al _{x3 Gay 3} N layer (0 ≦ x3 <1) as a laminated structure and an Al _x1 Gay ₁ N layer (0 ≦ x1 <x3 <) provided on the Al _{x3 Gay 3} N layer. 1). Further, the base 12 has, for example, an AlN layer as a laminated structure, an Al _{x3 Gay 3} N layer provided on the AlN layer (0 ≦ x3 <1), and an Al provided on the Al _{x3 Gay 3} N layer. _x1 Ga _y1 N layer (0 ≦ x1 <x3 <1 ) and the structure may have a containing. The base 12 may have a structure in which the composition is inclined. For example, base 12, _Al x Ga _y N layer is varied continuously or stepwise x from 1 to 0.6 (0 ≦ x <1) layer may have a.

The base 12 includes an AlN layer, an Al _x1 Gay ₁ N layer (0 ≦ x1 <1) provided on the AlN layer, and an upper region 121 provided on an upper surface of the Al _x1 Gay ₁ N layer. If there are, the upper region 121 is _{Al x1 Ga y1 N (x1 +} y1 = 1,0 ≦ x1 <1,0 <y1 ≦ 1) the thickness of the formed part and t nanometers (nm), the following equation ( 1) may be satisfied.
2 × exp (7 × (x1)) <t <10000 (1)

Here, in the present embodiment, the thickness t (nm) of the portion where the upper region 121 is formed of Al _x1 Ga _y1 N (hereinafter also referred to as “film thickness”) is perpendicular to the resonator surface 16. In an imaginary plane, at the intersection between the cross-section where the ridge portion semiconductor layer 332 is divided into two at the center as viewed from the direction of the resonator surface 16 and the upper surface 12 a of the base 12, Defined as length. In other words, the thickness of the portion upper area 121 are formed in the _{Al x1 Ga y1 N t (nm} ) is the length of the base 12 in a direction perpendicular to the upper surface 12a, and the upper surface 12a of the substrate 11.

  The thickness of the upper region 121 refers to the entire thickness of a continuous AlGaN composition layer even when AlGaN has a plurality of layers or has a composition distribution. That is, the upper region 121 is not limited to a region including only a layer formed with the same composition as the upper surface 12a.

When the thickness t (nm) of the portion where the upper region 121 is formed of Al _x1 Ga _y1 N satisfies the range shown in the expression (1), the base 12 is dissolved and removed by the chemical solution in the cleaning process at the time of manufacturing the laser diode 1. Thus, the AlN layer formed under Al _x1 Gay ₁ N and the substrate 11 are prevented from being exposed. In addition, by the upper region 121 is _Al x1 _{Ga y1} N The formed part of the thickness t (nm) satisfies the range shown in Equation (1), when the laser diode 1 is or is used for a long time in the environment of use Even when the base 12 is corroded by moisture in the air, the AlN layer formed under the Al _x1 Gay ₁ N and the substrate 11 are prevented from being exposed. By preventing the AlN layer and the substrate 11 from being exposed in the manufacturing process, the yield of the laser diode 1 in the process after the cleaning can be improved. Further, by preventing the AlN layer and the substrate 11 from being exposed in the use environment, it becomes possible to realize the laser diode 1 having a long life.

  A part of the upper region 121 is dissolved and removed in a cleaning process in the manufacturing process of the laser diode 1. For this reason, although the upper region 121 provided in the completed laser diode 1 is formed including all the regions on the upper surface of the base 12 where the first semiconductor layer 311 is not formed, all the regions are formed. In some cases, the thickness t (nm) (where t is not zero (t ≠ 0)) that satisfies the relationship of Expression (1) is not provided. That is, the upper region 121 provided in the completed laser diode 1 has a thickness t (nm) that satisfies the range of the expression (1) in at least a part of the region, but the expression (1) in the remaining region. ) May not have the thickness t (nm) satisfying the range (specifically, the thickness may be smaller than the lower limit of the formula (1)). However, damage to the upper region 121 from the outside is extremely small in a use environment as compared with a cleaning environment. For this reason, even if a part of the upper region 121 does not have the thickness t (nm) satisfying the range of the expression (1), the AlN layer and the substrate 11 are exposed in the use environment under the use environment. Can be sufficiently prevented, and the life can be extended.

On the other hand, in the manufacturing process of the laser diode 1, the upper region 121 has a thickness t (nm) that satisfies the range of the expression (1) in all regions after the upper region 121 is formed and before the cleaning step. doing. This prevents the AlN layer and the substrate 11 formed under the Al _x1 Ga _y1 N layer constituting the upper region 121 from being exposed in the cleaning step.

Here, the above equation (1) will be described in detail with reference to FIG. The horizontal axis of the graph shown in Figure 2, shows a _{Al x1 Ga y1 N (x1 +} y1 = 1,0 ≦ x1 <1,0 <y1 ≦ 1) of the Al composition ratio x1 constituting the upper region 121 of the base portion 12 I have. The vertical axis of the graph shown in FIG. 2 indicates the etching amount (nm) of Al _x1 Ga _y1 N (x1 + y1 = 1, 0 ≦ x1 <1, 0 <y1 ≦ 1) constituting the upper region 121 of the base 12. ing.

As a result of the inventor's intensive studies, under the conditions of a TMAH aqueous solution (tetramethylammonium hydroxide aqueous solution) having a concentration of 25% and a temperature of 85 ° C. for 5 minutes, as shown in FIG. It has been found that there is a relational expression of 2 × exp (7 × (x1)) between x1 and the removed film thickness (that is, the etching amount) of the base 12 dissolved and removed in the laminating direction. That is, when the thickness t (nm) of the portion where the upper region 121 is formed of Al _x1 Gay _y N is larger than 2 × exp (7 × (x1)), the base 12 is prevented from penetrating and removing in the stacking direction. Can be prevented. Therefore, for example, when the entire upper region 121 is formed of Al _x1 Ga _y1 N, it is possible to prevent the lower layer of the upper region 121 of the base 12 from being exposed.

Further, the upper region 121 is _Al x1 _{Ga y1} N The formed part of the thickness t (nm) is desirably less than 10000 nm. When the thickness t (nm) is smaller than 10000 nm, it is possible to suppress the occurrence of cracks that divide the laser diode 1 in the horizontal direction of the substrate 11 when forming the base 12.

  The conventional laser diode does not have the base 12 unlike the laser diode 1 according to the present embodiment. That is, using the reference numerals shown in FIG. 1, the conventional laser diode has a structure in which the nitride semiconductor element portion 13 is formed on the substrate 11. Therefore, in the conventional laser diode, the first semiconductor layer 311 is directly formed on the substrate 11. For this reason, in the conventional laser diode, when forming the first semiconductor layer 311, a chemical solution penetrates from a gap between the growth thin film for forming the first semiconductor layer 311 and the substrate 11, and the growth thin film is separated from the substrate 11. Failures occur frequently.

  On the other hand, in the laser diode 1 according to the present embodiment, since the base 12 is formed on the substrate 11, the substrate 11 may be exposed when forming the growth thin film for forming the first semiconductor layer 311. This prevents the chemical liquid from penetrating into the gap between the growth thin film and the substrate 11. As a result, in the manufacturing process of the laser diode 1, the number of defects in which the grown thin film peels from the base 12 is suppressed to a very small number.

(First semiconductor layer)

The first semiconductor layer 311 is formed on the base 12 and a part of the base 12. The first semiconductor layer 311 may have conductivity in order to supply electrons or holes to the light emitting unit 32. Examples of a material for forming the first semiconductor layer 311 include AlN, GaN, and a mixed crystal thereof. Specific examples of the material for forming the first semiconductor layer 311 _is an _{Al x Ga (1-x)} N (0 ≦ x ≦ 1). _{Al x Ga (1-x)} N in Al composition ratio x of forming a first semiconductor layer 311 may be the same as the _Al x1 _{Ga y1} N Al composition ratio x1 of the upper surface 12a of the base 12, the upper surface It may be smaller than the Al composition ratio x1 of Al _x1 Ga _y1 N of 12a. This makes it possible to suppress the occurrence of defects at the interface between the base 12 and the first semiconductor layer 311. Further, a material forming the first semiconductor layer 311 includes a group V element other than N such as P, As or Sb, a group III element such as In or B, C, H, F, O, Si, Cd, Zn, or An impurity such as Be may be contained.

When the first semiconductor layer 311 is an n-type semiconductor, it can be made n-type by, for example, doping Si with 1 × 10 ¹⁹ cm ⁻³ . When the first semiconductor layer 311 is a p-type semiconductor, the first semiconductor layer 311 can be made p-type by, for example, doping Mg by 3 × 10 ¹⁹ cm ⁻³ . The first semiconductor layer 311 may have a structure in which the composition is inclined. For example, the first semiconductor layer 311 may have a layer structure in which the Al composition ratio _{x of} AlxGa _(1-x) N is changed continuously or stepwise from 0.8 to 0.6. . The thickness of the first semiconductor layer 311 is not particularly limited. For example, the thickness may be 100 nm or more in order to reduce the resistance of the first semiconductor layer 311, or may be 10 μm or less from the viewpoint of suppressing generation of cracks when the first semiconductor layer 311 is formed.

(Mesa first semiconductor layer)
The mesa semiconductor layer 312 is formed on the first semiconductor layer 311 and in a part of the first semiconductor layer 311. By forming the mesa semiconductor layer 312 in a part of the first semiconductor layer 311, a region where the first electrode 14 is arranged on the upper surface of the first semiconductor layer 311 can be secured. The mesa semiconductor layer 312 may have conductivity in order to supply electrons or holes to the light emitting unit 32. Examples of a material for forming the mesa semiconductor layer 312 include AlN, GaN, and a mixed crystal thereof. Specific examples of the material for forming the mesa semiconductor layer 312 _is an _{Al x Ga (1-x)} N (0 ≦ x ≦ 1). _Al x _{Ga (1-x)} N in Al composition ratio x of the mesa semiconductor layer _{312, Al x Ga (1-x} ) may be the same as the N of the Al composition ratio x of the first semiconductor layer 311 , May be smaller than the upper surface of the first semiconductor layer 311. Here, the upper surface of the first semiconductor layer 311 is the surface on which the mesa semiconductor layer 312 is formed. This makes it possible to suppress the occurrence of defects at the lamination interface between the mesa semiconductor layer 312 and the first semiconductor layer 311. The material for forming the mesa semiconductor layer 312 includes a group V element other than N such as P, As or Sb, a group III element such as In or B, C, H, F, O, Si, Cd, Zn or An impurity such as Be may be contained.

When the mesa semiconductor layer 312 is an n-type semiconductor, it can be made n-type by doping 1 × 10 ¹⁹ cm ^{−3 of} , for example, Si. When the mesa semiconductor layer 312 is a p-type semiconductor, it can be made p-type by, for example, doping Mg by 3 × 10 ¹⁹ cm ⁻³ . Mesa semiconductor layer 312 _may have a Al _{x Ga (1-x)} is tilted structure an Al composition ratio of N. For example, the mesa semiconductor layer 312 _may have a _{Al x Ga (1-x)} N layer structure changing continuously or stepwise the Al composition ratio x of 0.8 from 0.6. The thickness of the mesa semiconductor layer 312 is not particularly limited. The thickness of the mesa semiconductor layer 312 may be 10 nm or more in order to efficiently confine the light emitted from the light emitting layer 322 to the light emitting section 32. The thickness of the mesa semiconductor layer 312 may be 5 μm or less from the viewpoint of reducing the resistance of the mesa semiconductor layer 312.

(Lower guide layer)
The lower guide layer 321 is formed on the mesa semiconductor layer 312. The lower guide layer 321 has a refractive index difference from the mesa semiconductor layer 312 in order to confine the light emitted by the light emitting layer 322 in the light emitting section 32. Examples of a material for forming the lower guide layer 321 include AlN, GaN, and a mixed crystal thereof. Specific examples of the material forming the lower guide layer 321 _{is Al x Ga (1-x)} N (0 ≦ x ≦ 1). The Al composition ratio x of Al _x Ga _(1-x) N forming the lower guide layer 321 is smaller than the Al composition ratio x of Al _x Ga _(1-x) N forming the mesa semiconductor layer 312. Good. Accordingly, the refractive index of the lower guide layer 321 is higher than that of the mesa semiconductor layer 312, and light emitted from the light emitting layer 322 can be confined in the light emitting section 32. The material for forming the lower guide layer 321 includes a group V element other than N such as P, As or Sb, a group III element such as In or B, C, H, F, O, Si, Cd, Zn or Be. And the like.

When the lower guide layer 321 is an n-type semiconductor, it can be made n-type by, for example, doping Si with 1 × 10 ¹⁹ cm ⁻³ . When the lower guide layer 321 is a p-type semiconductor, the lower guide layer 321 can be made p-type by doping, for example, 3 × 10 ¹⁹ cm ^{−3 of} Mg. The lower guide layer 321 may be an undoped layer. The lower guide layer 321 may have a structure in which the composition is inclined. For example, the lower guide layer 321 _may have a _{Al x Ga (1-x)} N layer structure changing continuously or stepwise the Al composition ratio x of 0.6 from 0.5. The thickness of the lower guide layer 321 is not particularly limited. The thickness of the lower guide layer 321 may be 10 nm or more in order to efficiently confine the light emitted from the light emitting layer 322 to the light emitting unit 32. The thickness of the lower guide layer 321 may be the resistance of the lower guide layer 321. May be 2 μm or less from the viewpoint of reducing the thickness.

(Light-emitting layer)
The light emitting layer 322 is a layer from which light emission of the laser diode 1 is obtained. Examples of a material for forming the light emitting layer 322 include AlN, GaN, and a mixed crystal thereof. Specific examples of the material forming the light emitting layer 322 _{is Al x Ga (1-x)} N (0 ≦ x ≦ 1). _{Al x Ga (1-x)} N in Al composition ratio x of the light-emitting layer 322, in order to confine carriers injected from the first electrode 14 and second electrode 15 to emit light efficiently section 32, Al of the lower guide layer 321 _It may be smaller than the Al composition ratio _{x of} xGa _(1-x) N. Further, a material forming the light emitting layer 322 includes a group V element other than N such as P, As or Sb, a group III element such as In or B, C, H, F, O, Si, Cd, Zn or Be. May be contained.

When the light-emitting layer 322 is an n-type semiconductor, it can be made n-type by, for example, doping Si with 1 × 10 ¹⁹ cm ⁻³ . In the case where the light-emitting layer 322 is a p-type semiconductor, the light-emitting layer 322 can be made p-type by, for example, doping Mg with 3 × 10 ¹⁹ cm ⁻³ . The light emitting layer 322 may be an undoped layer. Emitting layer 322 _may have a _{Al x Ga (1-x)} N in the Al composition ratio is tilted x structure. For example, the light emitting layer 322 _may have a _{Al x Ga (1-x)} N layer structure changing continuously or stepwise the Al composition ratio x of 0.5 from 0.4.

  The light emitting layer 322 has a barrier layer formed of, for example, AlGaN, and may have a multiple quantum well (MQW) structure in which well layers and barrier layers are alternately stacked one by one. Since the laser diode 1 includes the light emitting layer 322 having the multiple quantum well structure, the light emitting efficiency and the light emitting intensity of the light emitting layer 322 can be improved. The light emitting layer 322 may have, for example, a double quantum well structure of “barrier layer / well layer / barrier layer / well layer / barrier layer”. The thickness of each of these well layers may be, for example, 3 nm, the thickness of each of these barrier layers may be, for example, 10 nm, and the thickness of the light emitting layer 322 may be 36 nm.

(Upper guide layer)
The upper guide layer 323 is formed on the light emitting layer 322. The upper guide layer 323 has a different refractive index from the second semiconductor layer 331 in order to confine the light emitted by the light emitting layer 322 in the light emitting section 32. Examples of a material for forming the upper guide layer 323 include AlN, GaN, and a mixed crystal thereof. Specific examples of the material forming the upper guide layer 323 _{is Al x Ga (1-x)} N (0 ≦ x ≦ 1). _{Al x Ga (1-x)} N in Al composition ratio x of the upper guide layer 323 may be larger than the _{Al x Ga (1-x)} N in Al composition ratio x of the light-emitting layer 322. This makes it possible to confine carriers in the light emitting layer 322. The material for forming the upper guide layer 323 includes a group V element other than N such as P, As or Sb, a group III element such as In or B, C, H, F, O, Si, Cd, Zn or Be. And the like.

When the upper guide layer 323 is an n-type semiconductor, it can be made n-type by, for example, doping Si at 1 × 10 ¹⁹ cm ⁻³ . When the upper guide layer 323 is a p-type semiconductor, it can be made p-type by, for example, doping Mg with 3 × 10 ¹⁹ cm ⁻³ . The upper guide layer 323 may be an undoped layer. Upper guide layer 323 _may have a _{Al x Ga (1-x)} N is tilted Al composition ratio of the structure. For example, the upper guide layer 323 _may have a _{Al x Ga (1-x)} N layer structure changing continuously or stepwise the Al composition ratio x of 0.5 to 0.6 of. The thickness of the upper guide layer 323 is not particularly limited. The thickness of the upper guide layer 323 may be 10 nm or more in order to efficiently confine the light emitted from the light emitting layer 322 to the light emitting section 32. Further, the thickness of the upper guide layer 323 may be 2 μm or less from the viewpoint of reducing the resistance of the upper guide layer 323. The Al composition ratio x of Al _x Ga _(1-x) N (0 ≦ x ≦ 1) of each of the upper guide layer 323 and the lower guide layer 321 may be the same value or different values. Good.

(Second semiconductor layer)
The second semiconductor layer 331 is formed on the upper guide layer 323. The second semiconductor layer 331 may have conductivity in order to supply electrons or holes to the light emitting unit 32. Examples of a material for forming the second semiconductor layer 331 include AlN, GaN, and a mixed crystal thereof. Specific example of forming the second semiconductor layer 331 _is an _{Al x Ga (1-x)} N (0 ≦ x ≦ 1). _{Al x Ga (1-x)} N in Al composition ratio x of the second semiconductor layer 331 may be larger than the _{Al x Ga (1-x)} N in Al composition ratio x of the upper guide layer 323. As a result, a difference in refractive index occurs between the upper guide layer 323 and the second semiconductor layer 331, and light emitted from the light emitting layer 322 can be efficiently confined in the light emitting section 32. When the Al composition ratio x of Al _x Ga _(1-x) N of the second semiconductor layer 331 is larger than the Al composition ratio x of Al _x Ga _(1-x) N of the upper guide layer 323, the second Carriers injected from the electrode 15 can be efficiently confined in the light emitting section 32.

In addition, the second semiconductor layer 331 has an impurity such as a group V element other than N such as P, As or Sb, a group III element such as In or B, C, H, F, O, Si, Cd, Zn or Be. May be included. When the second semiconductor layer 331 is an n-type semiconductor, it can be made n-type by, for example, doping Si with 1 × 10 ¹⁹ cm ⁻³ . When the second semiconductor layer 331 is a p-type semiconductor, the second semiconductor layer 331 can be made to be p-type by doping, for example, 3 × 10 ¹⁹ cm ^{−3 of} Mg. The second semiconductor layer 331 _may have a Al _{x Ga (1-x)} is tilted structure an Al composition ratio of N. For example, the second semiconductor layer 331 _may have a _{Al x Ga (1-x)} N layer structure changing continuously or stepwise the Al composition ratio x of 0.8 from 0.3. The thickness of the second semiconductor layer 331 is not particularly limited. The thickness of the second semiconductor layer 331 may be 10 nm or more in order to efficiently confine the light emitted from the light emitting layer 322 to the light emitting unit 32. Further, the thickness of the second semiconductor layer 331 may be 5 μm or less from the viewpoint of reducing the resistance of the second semiconductor layer 331. The second semiconductor layer 331 may have a single-layer structure or a stacked structure. When the second semiconductor layer 331 has a stacked structure, for example the thickness is formed in the _u-Al 0.8 _{Ga 0.2} N is formed to be inclined to the composition of the p-Al x Ga _y N on a 20nm layer May have a layer with a thickness of 150 nm. p-Al x Ga _y N layer is inclined composition (composition gradient layer) _{from u-Al} 0.8 _{Ga 0.2} for example from a layer side which is formed by N Al composition ratio x of 0.8 to 0.3 The Ga composition ratio y may be inclined from 0.2 to 0.7.

(Ridge part semiconductor layer)
The ridge portion semiconductor layer 332 is formed on the second semiconductor layer 331 and on a part of the second semiconductor layer 331. By forming the ridge portion semiconductor layer 332 in a part of the second semiconductor layer 331, carriers injected from the second electrode 15 are prevented from diffusing in the ridge portion semiconductor layer 332 in the horizontal direction of the substrate 11. You. Thus, light emission in the light emitting layer 322 is controlled in a region located below the ridge portion semiconductor layer 332. As a result, the laser diode 1 can realize a high current density and reduce the threshold value of laser oscillation. The ridge section semiconductor layer 332 may have conductivity in order to supply electrons or holes to the light emitting section 32. Examples of a material for forming the ridge portion semiconductor layer 332 include AlN, GaN, and a mixed crystal thereof. Specific examples of the material forming the ridge semiconductor layer 332 _is an _{Al x Ga (1-x)} N (0 ≦ x ≦ 1). _Al x _{Ga (1-x)} N in Al composition ratio x of the ridge portion semiconductor layer _{332, Al x Ga (1-x} ) may be the same as the N of the Al composition ratio x of the second semiconductor layer 331 , May be large. Thereby, the second semiconductor unit 33 can efficiently transport the carriers injected from the second electrode 15 to the light emitting unit 32. The material for forming the ridge portion semiconductor layer 332 includes a group V element other than N such as P, As or Sb, a group III element such as In or B, C, H, F, O, Si, Cd, Zn, or An impurity such as Be may be contained.

When the ridge portion semiconductor layer 332 is an n-type semiconductor, it can be made n-type by doping, for example, Si at 1 × 10 ¹⁹ cm ⁻³ . In the case where the ridge portion semiconductor layer 332 is a p-type semiconductor, the p-type semiconductor can be formed by, for example, doping Mg with 3 × 10 ¹⁹ cm ⁻³ . Ridge semiconductor layer 332 _may have a Al _{x Ga (1-x)} is tilted structure an Al composition ratio of N. For example, ridge semiconductor layer 332 _may have a _{Al x Ga (1-x)} N layer structure changing continuously or stepwise the Al composition ratio x of 0.8 from 0.3. The thickness of the ridge portion semiconductor layer 332 is not particularly limited. The thickness of the ridge portion semiconductor layer 332 may be 10 nm or more in order to efficiently confine the light emitted from the light emitting layer 322 to the light emitting unit 32. The thickness of the ridge portion semiconductor layer 332 may be 5 μm or less from the viewpoint of reducing the resistance of the ridge portion semiconductor layer 332. The ridge semiconductor layer 332 may have a single-layer structure or a stacked structure. When the ridge portion semiconductor layer 332 has a stacked structure, for example, it is formed of p-Al _0.3 Ga _0.2 N and has a thickness of 20 nm and is formed of p-GaN on a layer having a thickness of 10 nm. The layers may be stacked.

(First electrode)
The first electrode 14 is formed on the first semiconductor layer 311. In the case where the first electrode 14 is an n-type electrode, a material for forming the first electrode 14 may be a general nitride if the first electrode 14 is used for the purpose of injecting electrons into the first semiconductor layer 311. It is possible to use a material corresponding to the N-type electrode of the semiconductor light emitting device. For example, as a forming material when the first electrode 14 is an n-type electrode, Ti, Al, Ni, Au, Cr, V, Zr, Hf, Nb, Ta, Mo, W and an alloy thereof, ITO, or the like is applied. You.

  In the case where the first electrode 14 is a p-type electrode, as a material for forming the first electrode 14, if the first electrode 14 is used for the purpose of injecting holes into the nitride semiconductor light emitting device, a general material is used. It is possible to use the same material as the p-type electrode layer of a typical nitride semiconductor light emitting device. For example, when the first electrode 14 is a p-type electrode, Ni, Au, Pt, Ag, Rh, Pd, Cu, an alloy thereof, ITO, or the like is applied. When the first electrode 14 is a p-type electrode, the contact resistance between the first electrode 14 and the first semiconductor layer 311 of the nitride semiconductor element portion 13 may be small, such as Ni, Au, an alloy thereof, or ITO. .

  The first electrode 14 may have a pad electrode on the upper part for the purpose of uniformly spreading the current over the entire area of the first electrode 14. Examples of a material for forming the pad electrode include Au, Al, Cu, Ag, and W. The pad electrode may be formed of Au having high conductivity among these materials from the viewpoint of conductivity. Specifically, as a structure of the first electrode 14, for example, a first contact electrode formed of an alloy of a material selected from Ti, Al, Ni, and Au is formed on the first semiconductor layer 311; In which the first pad electrode formed in step (1) is formed on the first contact electrode.

(Second electrode)
The second electrode 15 is formed on the ridge semiconductor layer 332. In the case where the second electrode 15 is an n-type electrode, a material for forming the second electrode 15 may be a general nitride if the second electrode 15 is used for the purpose of injecting electrons into the ridge portion semiconductor layer 332. It is possible to use a material corresponding to the n-type electrode of the semiconductor light emitting device. For example, as a forming material when the second electrode 15 is an n-type electrode, Ti, Al, Ni, Au, Cr, V, Zr, Hf, Nb, Ta, Mo, W, an alloy thereof, ITO, or the like is applied. You.

  In the case where the second electrode 15 is a p-type electrode, as a material for forming the second electrode 15, if the second electrode 15 is used for the purpose of injecting holes into the nitride semiconductor light emitting device, a general material is used. It is possible to use the same material as the p-type electrode layer of a typical nitride semiconductor light emitting device. For example, as a forming material when the second electrode 15 is a p-type electrode, Ni, Au, Pt, Ag, Rh, Pd, Cu and an alloy thereof, ITO, or the like is applied. When the second electrode 15 is a p-type electrode, the contact resistance between the second electrode 15 and the ridge portion semiconductor layer 332 of the nitride semiconductor element portion 13 may be Ni, Au, an alloy thereof, or ITO. .

  The second electrode 15 may have a pad electrode on the upper part for the purpose of uniformly diffusing the current over the entire area of the second electrode 15. Examples of a material for forming the pad electrode include Au, Al, Cu, Ag, and W. The pad electrode may be formed of Au having high conductivity among these materials from the viewpoint of conductivity. Specifically, as the structure of the second electrode 15, for example, a second contact electrode formed of an alloy of Ni and Au is formed on the ridge portion semiconductor layer 332, and a second pad electrode formed of Au is formed on the second pad electrode. And a structure formed on the contact electrode.

(Resonator surface)
The resonator surface 16 is formed on the same plane formed by the respective side surfaces of the first semiconductor unit 31, the light emitting unit 32, and the second semiconductor unit 33. The resonator surface 16 is provided for the purpose of reflecting light emitted from the light emitting section 32 on the resonator surface 16. In order to confine the light reflected by the resonator surface 16 in the light emitting section 32, the resonator surface 16 is provided in pairs on the light emission side of the laser diode 1 and on the side opposite to the emission side. Is also good. In order to reflect light emitted from the light emitting unit 32 on the resonator surface 16, the resonator surface 16 may be perpendicular and flat to a contact surface between the light emitting unit 32 and the upper guide layer 323. However, the resonator surface 16 may have an inclined portion or an uneven portion entirely or partially.

The Al composition ratio x of Al _x Ga _(1-x) N exposed on the resonator surface 16 may be 0 ≦ x ≦ 0.8 or 0 ≦ x ≦ 0.6. . As a result of intensive studies by the present inventors, it has been found that the resonator surface 16 has poor chemical resistance in the cleaning step and poor moisture resistance due to moisture in the air, and the Al composition of Al _x Ga _(1-x) N It was found that when the ratio x was within the range of 0 ≦ x ≦ 0.8 or 0 ≦ x ≦ 0.6, the occurrence of unevenness was small.

On the resonator surface 16, an insulating protective film such as a dielectric multilayer film and a reflective film may be formed. Specifically, the insulating protective film may be formed of SiO ₂ , and may be formed of Al ₂ O ₃ , SiN, SnO ₂ , ZrO, HfO ₂ , or the like. Further, the insulating protective film may have a structure in which these materials are stacked. The insulating protective film may be formed on both the light emission side of the resonator surface 16 of the laser diode 1 and the surface opposite to the light. The insulating protective film formed on the light emitting side of the resonator surface 16 and the insulating protective film formed on the light reflecting side may have the same structure or different structures. Good.

(Analysis method and observation method)
The material specification and composition ratio of the laser diode 1 in this embodiment can be analyzed by a method such as energy dispersive X-ray spectrometry (EDX) or Auger electron spectroscopy (Auger Electron Spectroscopy: AES). It is. The film thickness and distance of each film constituting the laser diode 1 are determined by dividing and polishing the laser diode 1 on a plane perpendicular to the cavity surface 16 or by processing a focused ion beam (FIB), and measuring the cross section thereof. The length can be measured by observing with a scanning electron microscope (SEM) or observing with a transmission electron microscope (TEM). Since a high-quality image can be easily obtained over a wide range, it is preferable to observe the image using an SEM.

(Production method)
The method for manufacturing the laser diode 1 according to the present embodiment will be described. In order to form the laser diode 1, a base 12, a first semiconductor layer 311, a mesa semiconductor layer 312, a lower guide layer 321, a light emitting layer 322, an upper guide layer 323, a second semiconductor layer 331 and a ridge are formed on a substrate 11. AlGaN for forming the respective semiconductor layers 332 is laminated in this order. The method of laminating these AlGaN layers is not particularly limited, but can be formed by, for example, a metal organic compound vapor phase epitaxy method (MOVPE method). In this growth method, for example, trimethylgallium (TMG), triethylgallium (TEG), trimethylaluminum (TMA), triethylaluminum (TEA) and ammonia (NH3) are supplied onto a substrate heated to an appropriate temperature. By performing a thermal decomposition reaction, a mixed crystal thin film of AlGaN can be grown. In addition, a molecular beam epitaxy method (MBE method) using a solid metal of Ga or Al as a group III raw material and using a gas such as NH ₃ or N ₂ as a raw material as a group V raw material can be used.

  The upper surface of the base 12, the first semiconductor layer 311 and the second semiconductor layer 331 is partially exposed by partially removing the structure in which the semiconductor layers formed of AlGaN are stacked by etching technology. It is possible. The AlGaN layer can be removed by using inductively coupled reactive ion etching as an etching technique. For example, the semiconductor layer can be removed by using chlorine as the ambient gas and setting the antenna power and the bias power to appropriate values. At this time, it is possible to control the etching depth by setting the treatment time to an appropriate time, and set the thickness of each of the base 12, the first semiconductor layer 311 and the second semiconductor layer 331 to a predetermined thickness. It is possible to control.

  As a method for forming the resonator surface 16, it is possible to form the resonator surface 16 only by using the above-described etching technique. However, the resonator surface 16 is planarized by additionally performing wet etching using a chemical solution. Is possible. For this wet etching, for example, a KOH aqueous solution or a TMAH aqueous solution can be used, and flattening can be performed by setting the temperature, treatment time, concentration, and the like of the chemical solution to appropriate values.

  As a method for forming the first electrode 14 and the second electrode 15, various techniques such as an electron beam evaporation method, a thermal evaporation method, and a sputtering method can be used. Further, in order to reduce the contact resistance between the first electrode 14 and the second electrode 15 and the nitride semiconductor element portion 13, after forming the metal thin film for forming the first electrode 14 and the second electrode 15, respectively. Heat treatment may be performed. By setting the heat treatment temperature, time, and atmosphere under appropriate conditions, a laser diode 1 having a low drive voltage and high power conversion efficiency can be realized.

  The method for forming an insulating layer on the resonator surface 16 and the nitride semiconductor element portion 13 is not particularly limited, but an insulating film can be formed by using, for example, a sputtering method.

  The laser diode 1 in a wafer state can be individually formed by combining a laser processing technique such as a laser scribe method or a laser ablation method or a processing technique such as a scribe method or a dicing method with a cleavage technique such as an expanding method or a breaking method. Can be After the laser diode 1 is divided into individual pieces, processing flaws, debris, and particles remain. Therefore, cleaning with water or an alkaline solution may be performed.

<Example>
Next, a nitride semiconductor laser diode according to an example of the present embodiment will be described with reference to FIGS. It should be noted that numerical values indicating the scale of the SEM image and a scale bar are shown at the lower right of the SEM images shown in FIGS. 3 to 5, respectively.

(Example 1)
On a c-plane sapphire substrate, trimethylgallium, trimethylaluminum, triethylaluminum, ammonia, silane, and cyclopentadienylmagnesium are used as source gases using an organometallic compound vapor phase growth apparatus (SR4338KS-HT, manufactured by Taiyo Nippon Sanso). Forming an AlN layer having a thickness of 2 μm, forming an n-Al _0.6 GaN layer corresponding to an upper region on the AlN layer, forming a base together with the AlN layer, and forming a first semiconductor layer having a thickness of An n-Al _0.6 GaN layer having a thickness of 1.9 μm was formed, and a u-Al _0.5 GaN layer having a thickness of 150 nm was formed as a lower guide layer on the n-Al _0.6 GaN layer. . Next, a u-Al _0.5 GaN layer having a thickness of 8 nm is formed as a barrier layer above the u-Al _0.5 GaN layer, and a u-Al layer having a thickness of 4 nm is formed as a first well layer above the barrier layer. _{A 0.3} GaN layer, a u-Al _0.5 GaN layer having a thickness of 8 nm as a barrier layer above the first well layer, and a u-Al layer having a thickness of 4 nm as a second well layer above the barrier layer. _A light emitting layer was formed by forming a _0.3 GaN layer and a u-Al _0.5 GaN layer having a thickness of 8 nm as a barrier layer on the second well layer in this order. Next, a 150 nm thick u-Al _0.5 GaN layer is formed as an upper guide layer on the light emitting layer, and an Al composition of 0.1 μm is formed on the u-Al _0.5 GaN layer as a second semiconductor layer. AlGaN continuously changed from 8 to 0.3 is formed as a composition gradient layer to a thickness of 150 nm, a p-GaN layer having a thickness of 10 nm is formed thereon, and a p-GaN layer is formed from the AlN layer. A laminated wafer is prepared.

On the wafer, Ni is deposited in a thickness of 100 nm using an electron beam evaporation apparatus using a predetermined patterning mask in each step, and chlorine gas is used using an inductively coupled reactive ion etching apparatus using the Ni as a mask. Is used as a reaction gas to form a ridge structure, a mesa structure, and a resonator structure. At this time, etching was performed so that 200 nm of n-Al _0.6 GaN remained as the base AlGaN layer.

  Using an electron beam evaporation apparatus, Ti, Al, Ti, and Au are evaporated to a thickness of 30 nm, 100 nm, 20 nm, and 150 nm, respectively, on the exposed upper surface of the first semiconductor layer using an electron beam evaporation apparatus. And heated at 900 ° C. for 3 minutes in a nitrogen atmosphere. Pd, Pt, and Au are deposited on the upper surface of the second semiconductor layer to a thickness of 10 nm, 10 nm, and 40 nm, respectively, as a second electrode using an electron beam evaporation apparatus, and then, under a nitrogen atmosphere using a high-temperature heat treatment apparatus. At 600 ° C. for 5 minutes. Ti and Au were vapor-deposited on the first electrode and the second electrode to a thickness of 50 nm and 400 nm, respectively, as pad electrodes to produce a laser diode having a wavelength of 285 nm.

To wash the laser diode, it was immersed in a 25% aqueous solution of tetramethylammonium hydroxide (TMAH) at 85 ° C. for 5 minutes.
As shown by the dashed ellipse in FIG. 3, the n-Al _0.6 GaN layer corresponding to the upper region of the base was etched along the thin film growth direction. However, the etching amount was 125 nm, and the n-Al _0.6 GaN layer corresponding to the upper region of the base remained at a thickness of 75 nm. Therefore, defects such as peeling of a thin film for forming the first semiconductor layer did not occur.

(Example 2)
An AlN layer having a thickness of 2 μm is formed on a c-plane sapphire substrate using trimethylgallium, trimethylaluminum, and ammonia as source gases using an organometallic compound vapor phase growth apparatus (manufactured by Taiyo Nippon Sanso; SR4338KS-HT). A u-Al _0.7 GaN layer (having a thickness of 2 μm) corresponding to an upper region is formed on the AlN layer as a base together with the AlN layer, and an AlN layer and a u-Al _0.7 GaN layer are formed. Is prepared. Depositing a 100-nm thick Ni film on the wafer using an electron beam vapor deposition apparatus, and performing etching using chlorine gas as a reactive gas using an inductively coupled reactive ion etching apparatus using the Ni as a mask. Then, the u-Al _0.7 GaN layer is partially removed. At this time, etching was performed so that a 250 nm thick u-Al _0.7 GaN layer remained as an AlGaN layer corresponding to the upper region of the base.

The wafer was immersed in a 25% aqueous solution of tetramethylammonium hydroxide (TMAH) at 85 ° C. for 5 minutes in order to clean the wafer, and the u-Al _0.7 GaN layer was etched along the thin film growth direction. However, the etching amount was 225 nm, and the u-Al _0.7 GaN layer corresponding to the upper region of the base remained with a thickness of 25 nm. Therefore, defects such as peeling of the thin film formed on the substrate did not occur.

  FIG. 2 shows a result obtained by performing a similar experiment in this example by changing the Al composition ratio of the u-AlGaN layer and measuring the etching amount. As shown in FIG. 2, it can be seen that the u-AlGaN layer formed on the substrate is not penetrated by etching if the thickness t (nm) is within the range satisfying the above equation (1). .

(Comparative Example 1)
A wafer formed in the same manner as in Example 1 above was prepared, except that etching was performed so that an n-Al _0.6 GaN layer of 100 nm remained as an AlGaN layer constituting a base. To wash the wafer, the wafer was immersed in a 25% aqueous solution of tetramethylammonium hydroxide (TMAH) at 85 ° C. for 15 minutes.

In this comparative example, the thickness of the n-Al _0.6 GaN layer formed on the AlN layer is 100 nm, which is not included in the range of the above formula (1). For this reason, as shown by the downward straight arrow in FIG. 4, the n-Al _0.6 GaN layer penetrates and is removed at a distance of 1.5 μm from the etching end face, and the lower AlN is also removed. As a result, the sapphire substrate was exposed.

(Comparative Example 2)
A 1.7 μm thick AlN layer was formed on a c-plane sapphire substrate using trimethylgallium, trimethylaluminum, and ammonia as source gases using an organometallic compound vapor phase epitaxy apparatus (SR4338KS-HT, manufactured by Taiyo Nippon Sanso). Forming a 100 nm thick u-Al _0.7 Ga _0.3 N layer on the AlN layer, and forming a 150 nm thick u-Al _0.7 Ga _0.3 N layer on the u-Al _0.7 Ga _0.3 N layer. -Al _0.3 Ga _0.7 N layer is formed, and a 300 nm thick u-Al _0.1 Ga _0.9 N layer is formed on the u-Al _0.3 Ga _0.7 N layer. Then, a wafer having these layers laminated is prepared.

On the wafer, Ni having a thickness of 100 nm was deposited using an electron beam evaporation apparatus, and etching was performed using chlorine gas as a reactive gas with an inductively coupled reactive ion etching apparatus using the Ni as a mask. . At this time, etching was performed so that a 50 nm u-Al _0.7 Ga _0.3 N layer remained as an AlGaN layer constituting the base. FIG. 5 shows the result of immersing the wafer in a 25% aqueous solution of tetramethylammonium hydroxide (TMAH) at 85 ° C. for 30 minutes for cleaning.

On the left side in FIG. 5, an SEM image of a cross section of an etched portion from the sapphire substrate of the wafer to the u-Al _0.1 Ga _0.9 N layer is shown. The center in FIG. 5 shows an enlarged SEM image of a cross section of the etched portion from the AlN layer to the u-Al _0.1 Ga _0.9 N layer of the wafer. On the right side in FIG. 5, the layer structure of the wafer is schematically shown.

Also in this modified example, the thickness of the u-Al _0.7 Ga _0.3 N layer formed on the AlN layer is 50 nm, which is not included in the range of the above-described formula (1). Therefore, as shown on the left side in FIG. 5, the u-Al _0.7 Ga _0.3 N layer is etched away along the thin film growth direction, and the lower AlN is also removed, exposing the sapphire substrate. . Further, as shown in the center of FIG. 5, the side surface of the AlN layer is extremely concave, and the side surface of u-Al _0.7 Ga _0.3 N is also largely concave, indicating that side etching is progressing. Was.
From the above results, the cavity surface of the nitride semiconductor laser diode is _preferably formed by _{Al x2 Ga y2 N (x2 +} y2 = 1,0 ≦ x2 ≦ 0.8,0.2 ≦ y2 ≦ 1) and it is more preferably formed by _{Al x2 Ga y2 N (x2 +} y2 = 1,0 ≦ x2 <0.7,0.3 <y2 ≦ 1).

As described above, the laser diode 1 according to the present embodiment includes the base 12 provided on the substrate 11, the first semiconductor layer 311 provided on a part of the upper surface of the base 12, and the first semiconductor layer 311. A light emitting unit 32 provided on a part of the upper surface, and the base 12 is a region where the first semiconductor layer 311 is not formed, and is formed of Al _x1 Gay _y N (x1 + y1 = 1, 0 ≦ x1 <1, 0 <y1 ≦ 1), and has an upper region 121 including the upper surface 12a.

  The laser diode 1 having such a configuration can prevent the AlN layer and the substrate 11 from being exposed in the manufacturing process, so that the manufacturing yield can be improved. Further, the laser diode 1 having such a configuration can prevent the AlN layer and the substrate 11 from being exposed in a use environment, and can extend the life.

1 Nitride semiconductor laser diode (laser diode)
Reference Signs List 4 light emitting unit 11 substrate 12 base 12a upper surface 13 nitride semiconductor element unit 14 first electrode 15 second electrode 16 resonator surface 31 first semiconductor unit 32 light emitting unit 33 second semiconductor unit 121 upper region 311 first semiconductor layer 312 mesa Part semiconductor layer 321 Lower guide layer 322 Light emitting layer 323 Upper guide layer 331 Second semiconductor layer 332 Ridge part semiconductor layer

Claims (4)

A base provided on the substrate,
A first semiconductor layer provided on a part of the upper surface of the base,
A light-emitting unit provided on a part of the upper surface of the first semiconductor layer,
With
The base comprises an upper region including the upper surface formed by a said first semiconductor layer is not formed area _{Al x1 Ga y1 N (x1 +} y1 = 1,0 ≦ x1 <1,0 <y1 ≦ 1) A nitride semiconductor laser diode. When the upper area _{Al x1 Ga y1 N (x1 +} y1 = 1,0 <x1 <1,0 <y1 <1) the thickness of the formed part and t nm,
2 × exp (7 × (x1)) <t <10000
The nitride semiconductor laser diode according to claim 1, wherein: The nitride semiconductor laser diode according to claim 1, wherein the base includes AlN. At least including a side surface of the first semiconductor layer and the light emitting unit, a resonator surface provided on a side surface in a direction in which light is emitted to the outside,
The resonator _{surface, Al x2 Ga y2 N (x2} + y2 = 1,0 ≦ x2 ≦ 0.8,0.2 ≦ y2 ≦ 1) according to claims 1, which is formed in any one of 3 Nitride semiconductor laser diode.