JPH11251631A - Nitride semiconductor element and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nitride semiconductor element capable of having an effective reflecting mirror to be an excellent resonator on a surface light emitting laser also improving the photo-detecting efficiency of the light emitting element, by effectively reflecting the leakage light mainly on the substrate side in an LED. SOLUTION: This nitride semiconductor element is structured of the first nitride semiconductor layer 2 grown on a dissimilar substrate 1 so as to form irregularities thereon exposing the sides thereof having the first protective films 3 on the upper plane of the projection, while the second protective film 4 on the under plane of the recession on the second nitride semiconductor layer 5 developing less crystal defects than the first nitride semiconductor layer 2 grown from the sides of the irregularities. In such a constitution, at least one out of the first and second protective films 3 and 4 fills the role of a reflecting mirror made of a dielectric multilayer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting element such as an LED (light emitting diode), an LD (laser diode) or a superluminescent diode (SLD), a light receiving element such as a solar cell or an optical sensor, or a transistor. Nitride semiconductors used for electronic devices such as power devices (In _X Al _Y Ga _{1 -XYN} , 0 ≦ X, 0 ≦ Y, X +
The present invention relates to a nitride semiconductor device using Y ≦ 1) and a method for manufacturing the same, particularly a nitride semiconductor device having an element structure formed on a nitride semiconductor substrate having few crystal defects to improve luminous efficiency and life characteristics, and the like. It relates to a manufacturing method.

[0002]

2. Description of the Related Art Recently, blue LEDs made of nitride semiconductors have been developed.
And green LEDs have already been put to practical use. The LED has a double hetero structure in which n-type and p-type nitride semiconductors are stacked on a sapphire substrate, and the active layer has a quantum well structure nitride semiconductor layer. The nitride semiconductor light emitting devices constituting the LED are classified into two types: a case where the sapphire substrate side is used as a light emission observation surface side and a case where the nitride semiconductor layer side is used as a light emission observation surface side. First, when the sapphire substrate side is used as a light emission observation surface, since the positive and negative electrodes are provided on the same surface side of the nitride semiconductor, when connecting the electrodes to a support such as a lead frame, for example, the However, there is a disadvantage that the chip size becomes large and the handling property is deteriorated in view of preventing short circuit. On the other hand, in this case, since the property of transparent sapphire is actively utilized, there is an advantage that the light extraction efficiency is improved. Next, when the nitride semiconductor side is used as the light emission observation surface, the chip size can be reduced, and the handleability is much better than the former case. On the other hand, when the nitride semiconductor side is used as the light emission observation surface, there is a disadvantage that light leaking to the sapphire substrate side is absorbed by, for example, an adhesive of a lead frame and light extraction efficiency is deteriorated. Such broadly divided two types of LEDs have advantages and disadvantages, respectively. However, from the viewpoint of simplification of the manufacturing process, etc., the latter having better handleability is selected and generally commercially available. I have. Further, in the latter case, in order to solve the problem that light leaks to the sapphire substrate side and the light extraction efficiency is reduced, for example, Japanese Patent Application Laid-Open No. 9-64421 discloses that
A technique has been described in which a light reflecting film is formed on a surface of the substrate that does not have an element structure, so that light leaking to the substrate side is reflected to a light emission observation surface side of the nitride semiconductor layer side to improve luminous efficiency. I have.

Further, the present inventors have proposed, as a nitride semiconductor LD element capable of continuous oscillation, a laser element having a stripe type waveguide and having a cleavage plane or an etching plane at an end face of an active layer as a resonance plane; A surface emitting laser device that emits laser light in a direction perpendicular to a substrate has been proposed. Among the above two types of laser devices, the surface emitting laser is useful for lowering the threshold value of the laser device and stabilizing the horizontal mode, the vertical mode, and the like. The surface emitting laser element is easy to reduce the laser beam diameter and is very advantageous as a DVD light source. Further, it is easy to obtain a single transverse mode, and is also desirable in the optical communication field where a single transverse mode is required. . As surface emitting nitride semiconductor laser devices proposed by the present inventors, for example, JP-A-7-335975 and JP-A-8-26
Nos. 4891 and 8-321660, a surface emitting laser device having a reflecting mirror formed on the sapphire substrate surface and the uppermost portion of the p-side layer, and one reflecting mirror formed on the substrate surface or the uppermost layer of the nitride semiconductor. A surface emitting laser device having the other reflecting mirror formed at a position distant from the device, and a semiconductor having a function of a reflecting mirror laminated on the n-side of the active layer, and the other reflecting mirror is formed on a substrate surface or a nitride semiconductor. Describes a surface emitting laser element formed on the uppermost layer of the above.

[0004]

However, the above L
In the latter case of the ED (the nitride semiconductor side is used as the light emission observation surface), the technology of forming a light reflection film on the sapphire substrate surface to reflect light leaking to the sapphire substrate side has improved the luminous efficiency to some extent, Not satisfactory. Furthermore, in the above-mentioned known surface emitting laser element, the distance between the active layer and the reflecting mirror is too long, so that it is difficult to use the reflecting mirror as a resonator. In the technique of forming a multilayer film of Al _a Ga _1-a N / Al _b Ga _1-b N before growing the active layer, the active layer tends to be difficult to grow with good crystallinity.

Accordingly, an object of the present invention is to improve the light extraction efficiency of a light emitting element by effectively reflecting light mainly leaking to a substrate side in an LED, and to provide a good cavity in a surface emitting laser. It is an object of the present invention to provide a nitride object device capable of having an effective reflecting mirror and a method of manufacturing the same.

[0006]

That is, the present invention can achieve the object of the present invention by the following constitutions (1) to (3). (1) An unevenness is formed on a first nitride semiconductor layer grown on a heterogeneous substrate made of a material different from that of a nitride semiconductor, and a side surface of the first nitride semiconductor layer in the uneven portion is exposed. A first protective film on the upper flat surface of the convex portion and a second protective film on the lower flat surface of the concave portion, and grown from the side surface of the concave and convex portion where the first and second protective films are not formed. A nitride semiconductor device having an element structure on a second nitride semiconductor layer having fewer crystal defects than the first nitride semiconductor layer,
A nitride semiconductor device, wherein at least one of the first protective film and the second protective film is a reflector formed of a dielectric multilayer film. (2) a first step of growing a first nitride semiconductor layer on a heterogeneous substrate made of a material different from a nitride semiconductor, and after the first step, irregularities are formed in the first nitride semiconductor layer. The first protective film is formed to expose the side surface of the first nitride semiconductor layer, a first protective film on which the nitride semiconductor does not grow or hardly grows is formed on the upper flat surface of the convex portion, and the nitride semiconductor is formed on the lower flat surface of the concave portion. A second step of forming a second protective film that does not grow or hardly grows, and, after the second step, growing a second nitride semiconductor layer from the exposed side surface of the first nitride semiconductor layer A third step of forming a nitride semiconductor substrate by forming an element structure including a plurality of nitride semiconductor layers on the nitride semiconductor substrate obtained in the third step. A first protection film and a second protection film formed in the second step. A method for manufacturing a nitride semiconductor device, wherein one of the films is a reflector formed of a dielectric multilayer film. (3) The method for growing a nitride semiconductor according to (2), wherein, in the second step, a lower surface of the concave portion is a first nitride semiconductor layer surface or a heterogeneous substrate surface.

That is, according to the present invention, a nitride semiconductor is grown using lateral growth of the nitride semiconductor, which can reduce crystal defects.
(growth: lateral growth), a nitride semiconductor with very few crystal defects can be obtained, and the protective film used in the lateral growth has a function of reflecting light, thereby solving the above conventional problems. can do. As described above, according to the present invention, a nitride semiconductor with very few crystal defects is grown by lateral growth, and an element structure is formed thereon, so that an element structure with good crystallinity can be obtained. The luminous efficiency is improved as compared with the case where the number is large. Furthermore, the present invention adds a function of reflecting light to a protective film used in lateral growth, that is, by using a reflecting mirror made of a dielectric multilayer film as a protective film, an LED can prevent light leaking to the substrate side. Since the light can be reflected by the protective film, the luminous efficiency is further improved. In the case of the surface emitting laser, a protective film capable of reflecting light at a short distance from the active layer and without impairing the crystallinity of the element structure is formed. Therefore, it is possible to obtain a good reflecting mirror which becomes a resonator of the surface emitting laser. As described above, when the reflector is close to the active layer, the distance between the reflectors (resonator length) can be reduced, so that the internal loss of the resonator due to absorption or the like decreases and the oscillation threshold value tends to decrease. is there.

Conventionally, as a substrate for growing a nitride semiconductor, there is no substrate that lattice-matches with the nitride semiconductor. For example, sapphire, spinel, silicon carbide, or the like has been used as the substrate. Many crystal defects occur in a nitride semiconductor grown on such a substrate that does not have lattice matching, and a nitride semiconductor cannot be obtained as a good crystal. Crystal defects are dislocations in a nitride semiconductor that forms an element structure, and are one factor that degrades the performance of the element. As a device formed by performing a method of growing a nitride semiconductor to reduce crystal defects which cause a reduction in performance and forming a device structure thereon, for example, the present inventors have proposed a method in which Ga is deposited on a sapphire substrate.
After growing an N film to about 2 μm, a protective film made of SiO ₂ is formed in a stripe shape so as to have a width of 8 μm along the laser resonance direction and a distance of 4 μm between the protective films, and the protective film is formed. Start growing vertically from the part that is not
Subsequently, when a GaN film having a thickness of 10 μm is grown laterally on the protective film and a GaN film having a thickness of 10 μm is formed, a GaN single crystal film having few crystal defects and a small number of crystal defects on the protective film is obtained. By growing an element structure on this GaN single crystal film with few crystal defects, a wavelength of about 400 nm and an optical output of 2
It has been announced that a nitride semiconductor laser device capable of achieving continuous oscillation of about 10,000 hours at mW can be obtained (for example, "In
Present Status of GaN-Based Multiple Quantum Well Structure Semiconductor Laser ", 5th
Eighth Annual Meeting of the Japan Society of Applied Physics, Lecture No. 4aZC-2,
October 1997, "Present Status
of InGaN / AlGaN based Las
er Diodes ", The Second Int
electronic Conference onN
itride Semiconductors (IC
NS'97), lecture number S-1, October 1997, etc.). A method of growing a nitride semiconductor on such a protective film by utilizing the lateral growth of the nitride semiconductor is called lateral over growth.

[0009] In contrast to such known techniques, the present invention provides:
A first nitride semiconductor layer was grown on a heterogeneous substrate such as sapphire to form an uneven portion, a first protective film was formed on an upper flat surface of the convex portion, and a second protective film was formed on a lower flat surface of the concave portion. rear,
By growing the second nitride semiconductor, the growth of the nitride semiconductor in the vertical direction is once suppressed, and after growing first in the horizontal direction only, and then growing in the horizontal and vertical directions, dislocation of crystal defects and The generation is reduced, and a second nitride semiconductor layer having good crystallinity can be obtained. In the above-described conventional lateral growth, the growth of the nitride semiconductor in the vertical direction is only partially suppressed. However, the present invention suppresses substantially all the vertical growth and only the growth in the horizontal direction. And growth in both lateral directions. Further, the present invention provides a protective film used for such lateral growth, in addition to the property that nitride semiconductors are unlikely to grow, and a function of reflecting light. A simple reflecting mirror can be obtained. Moreover, since it can be formed at a position closer to the active layer as compared with the position where the conventional reflecting mirror is formed, the function as a reflecting mirror is improved. Is a protective film used for lateral growth, so that the crystallinity of the element structure can be maintained well without impairing the crystallinity. Therefore, the present invention
It is possible to obtain a light emitting diode having a good reflecting mirror and improved light emission efficiency, and a surface emitting laser element having a reflecting mirror that can be a good resonator, and further provide a manufacturing method capable of obtaining them. it can. Hereinafter, in the specification, the second nitride semiconductor may be simply referred to as a nitride semiconductor substrate or a substrate.

In the surface emitting laser, since the reflecting mirror is a Fabry-Perot type flat reflecting mirror, if the reflecting mirror is far from the active layer, there is a possibility that the feedback rate of resonating light is lost. Since the mirror can be formed at a position close to the active layer, the light feedback rate is good.

In the present invention, any one of the first protective film and the second protective film may be a reflecting mirror composed of a dielectric multilayer film, and preferably both are reflecting mirrors composed of a dielectric multilayer film. This is desirable because it improves the luminous efficiency of the LED and the usefulness of the surface emitting laser as a reflector.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The nitride semiconductor device of the present invention and a method of manufacturing the same will be described in more detail with reference to FIGS.

FIG. 1 is a schematic sectional view showing a nitride semiconductor device according to one embodiment of the present invention. In FIG.
An uneven portion is formed on the surface of a first nitride semiconductor layer 2 formed on a heterogeneous substrate 1 different from the nitride semiconductor, and a first protective film 3 and a lower portion of the concave portion are formed on an upper flat surface of the convex portion. A second protective film 4 is provided on a plane, and the first protective film 3 and the second
A nitride semiconductor device is described in which a second nitride semiconductor layer 5 grown from the side surface of the uneven portion where the protective film 4 is not formed is used as a substrate and has an element structure on the substrate. Further, in the present invention, the first protective film 3 and / or the second protective film 4 are dielectric multilayer films.

According to the method of growing a nitride semiconductor using lateral growth as the second nitride semiconductor layer (nitride semiconductor substrate) of the present invention, the first nitride semiconductor is partially provided with irregularities. Forming a first protective film on the upper surface of the convex portion,
By forming the second protective film on the lower plane of the concave portion, it is possible to prevent crystal defects generated on the surface of the heterogeneous substrate from being continuously dislocated. Further, when the first and second protective films are formed as described above, the nitride semiconductor is difficult to grow on the protective film. Therefore, the growth of the second nitride semiconductor is selectively performed on the first nitride semiconductor. Growth begins in the lateral direction from the side surface of the uneven portion where the protective film is not formed. Here, in the process of growing the nitride semiconductor in the lateral direction, the number of dislocations in the crystal defects generated on the surface of the heterogeneous substrate is extremely smaller than in the case where the nitride semiconductor grows in the vertical direction. Further, it is presumed that the crystal defects that have been dislocated in the lateral direction hardly cause dislocation when the nitride semiconductor starts to grow from the lateral direction to the longitudinal direction. As a result, a second nitride semiconductor having almost no crystal defects and having excellent crystallinity can be obtained as a thick film. Here, the nitride semiconductor is difficult to grow on the protective film, but the second nitride semiconductor continues to grow in the horizontal and vertical directions, so that the protective film is as if growing on the protective film. Grow over the

Further, a new protective film may be formed on a portion of the surface of the second nitride semiconductor where crystal defects appear, and a new nitride semiconductor may be grown thereon. Crystal defects can be reduced. In this case, the new protective film may or may not have a reflection function, but preferably has a reflection function since luminous efficiency is improved. In the case of a surface-emitting laser, it is formed at a position facing the other reflecting mirror provided on the uppermost layer of the element structure (for example, the p-electrode 27 is paired with a reflecting mirror made of a protective film in FIG. 9). It is preferable that the new protective film has at least a reflection function. When the new protective film has a reflection function, it becomes easy to remove the heterogeneous substrate, the first and second protective films and the second nitride semiconductor, and the new protective film is formed after forming the new protective film. A new nitride semiconductor can be used as the substrate.

Further, when a nitride semiconductor device is produced using a second nitride semiconductor having excellent crystallinity with very few crystal defects obtained by the above-described growth method utilizing lateral growth as a substrate, Similarly, the nitride semiconductor device grown on this layer is also a device having good crystallinity without crystal defects, which is significantly prevented from being deteriorated due to crystal defects, and the life time is improved. In addition, it is possible to provide a nitride semiconductor device having good life characteristics. Furthermore, in addition to improving the performance of the device by reducing such crystal defects, by providing the protective film used for lateral growth with a light reflecting function, the luminous efficiency is further improved, and the good reflection by the surface emitting laser is achieved. Become a mirror.

Further, according to the present invention, an uneven portion is formed on a first nitride semiconductor layer 2 formed on a heterogeneous substrate 1 different from a nitride semiconductor, and a first protective film 3 and a concave portion are formed on an upper flat surface of the convex portion. After the second protective film 4 is formed on the lower surface of the substrate and the second nitride semiconductor layer is grown to form a nitride semiconductor substrate, the heterogeneous substrate 1 is formed before an element structure is formed on the substrate. May be removed before forming the element structure.

FIG. 2 is a schematic cross-sectional view showing one embodiment of a method for growing a second nitride semiconductor layer to be a nitride semiconductor substrate according to the present invention shown in FIGS. The method for growing the second nitride semiconductor layer will be described in more detail with reference to FIG.

As one embodiment of the second nitride semiconductor layer growing method of the present invention, first, in a first step of FIG. 2, a first nitride semiconductor layer 2 is grown on a heterogeneous substrate 1. In the second step of FIG. 3, the first nitride semiconductor 2
In order to control the direction of growth of the first nitride semiconductor 2, a first protective film is formed on the upper flat surface of the projection to form a projection and a depression on the surface of the first nitride semiconductor 2 to expose the side surface of the first nitride semiconductor 2. 3, a second protective film 4 is formed on the lower plane of the concave portion, and subsequently, in a third step of FIG. 4, the first nitride semiconductor 2 whose growth direction is controlled, ie, the first nitride semiconductor 2, is formed. The second nitride semiconductor 5 is grown from the side surface of the nitride semiconductor 2 to form a nitride semiconductor substrate.

Hereinafter, each of the above steps will be described in more detail with reference to the drawings. FIG. 2 is a schematic step view in which a first step of growing a first nitride semiconductor 2 on a heterogeneous substrate 1 is performed. In the first step, as the heterogeneous substrate 1 that can be used, for example, sapphire or spinel (MgA1) having any one of the C-plane, the R-plane, and the A-plane as a main surface is used.
Insulating substrate such as ₂ O ₄ ), SiC (6H, 4H, 3C)
, ZnS, ZnO, GaAs, Si, and an oxide substrate lattice-matched with a nitride semiconductor, and a substrate material different from a conventionally known nitride semiconductor can be used. Preferred heterosubstrates include sapphire and spinel.

In the first step, before growing the first nitride semiconductor 2 on the heterogeneous substrate 1,
A buffer layer (not shown) may be formed thereon. As the buffer layer, Al _X Ga _{1 -X} N (0 ≦ X ≦
A composition having the composition 1) can be used. The buffer layer is grown at a low temperature of 200 ° C. to 900 ° C., and may have a thickness of at least 1 atom.
It is grown with a film thickness of μm to 10 Å. When the buffer layer is formed on the heterogeneous substrate 1 in the above temperature range in this manner, the lattice constant between the heterogeneous substrate 1 and the first nitride semiconductor 2 is reduced, and crystal defects of the first nitride semiconductor 2 are reduced. Tend to be. As a buffer layer, for example, Z
A layer made of a semiconductor different from a nitride semiconductor such as nO may be used as the buffer layer.

In the first step, the first nitride semiconductor 2 formed on the heterogeneous substrate 1 includes undoped GaN, Si, G
GaN doped with n-type impurities such as e and S can be used. The concentration of the n-type impurity is 1 × 10 ¹⁷ / cm
³ or less. The first nitride semiconductor 2 is grown on the heterogeneous substrate 1 at a high temperature, specifically 900 ° C. to 1100 ° C., preferably 1050 ° C. Although the thickness of the first nitride semiconductor 2 is not particularly limited, it is 100
Angstrom or more, preferably about 1 to 10 μm,
More preferably, it is desirable to form a film having a thickness of 1 to 5 μm.

Next, FIG. 3 shows that after the first nitride semiconductor 2 is grown on the heterogeneous substrate 1, the first nitride semiconductor 2 is deposited on the first nitride semiconductor 2.
An uneven portion is formed to such a depth that the nitride semiconductor 2 slightly remains to expose the side surface of the first nitride semiconductor 2 and a first protective film is formed on the upper flat surface of the convex portion as shown in FIG. Form 3
FIG. 9 is a schematic cross-sectional view showing a second step of forming a second protective film 4 on the lower plane of the concave portion and suppressing the vertical growth of the first nitride semiconductor 2 to perform only the horizontal growth. is there. In the second step, the order of the formation of the uneven portion and the formation of the protective film is not particularly limited, and is performed, for example, by a method described later.

In the second step, forming irregularities means that the heterogeneous substrate 1 is formed from the surface of the first nitride semiconductor 2 so that at least the side surfaces of the first nitride semiconductor 2 are exposed.
The first nitride semiconductor 2 may be provided with irregularities in any shape as long as the depressions are formed in the direction of. For example, the first nitride semiconductors 2 can be formed into random depressions, stripes, grids, or dots. The concavo-convex portion partially provided in the first nitride semiconductor 2 is formed halfway in the first nitride semiconductor 2 or at a depth reaching a heterogeneous substrate, and the depth of the concave portion of the concavo-convex portion is The value depends on the film thickness of the first nitride semiconductor 2 and the film thickness of the second protective film 4 formed below the concave portion. It is preferable to form an uneven portion so as to obtain a side surface having a shape in which the second nitride semiconductor 5 that grows on the surface can easily grow. It is preferable that the depth of the depression of the uneven portion is such a depth that the first nitride semiconductor 2 remains. For example, when forming an uneven portion, a heterogeneous substrate 1
Is exposed, it is considered that it is difficult to form the second protective film 4 near the side surface of the first nitride semiconductor 2 when the second protective film 4 is formed. If the surface of the heterogeneous substrate 1 is not sufficiently covered, the second nitride semiconductor 5 may grow on the surface of the heterogeneous substrate 1 and crystal defects may be generated therefrom. Although the specific depth of the depression of the uneven portion is not particularly limited, it is, for example, 500 Å to 5 μm.

When the shape of the uneven portion is a stripe shape,
As a specific shape of the stripe, for example, a stripe having a width of 10 to 20 μm and a stripe interval of 2 to 5 μm can be formed.

As a method of providing the concave and convex portions in the second step, any method may be used as long as it can remove a part of the first nitride semiconductor, and examples thereof include etching and dicing. When forming irregularities on the first nitride semiconductor 2 by etching, using a mask pattern of various shapes in photolithography technology, a stripe-shaped or grid-shaped photomask is formed, and the resist pattern is formed. The first nitride semiconductor 2 can be formed by etching. Further, an off-trif method may be performed using a mask having the above shape.
When dicing is performed, for example, it can be formed in a stripe shape or a grid shape.

The method of etching the nitride semiconductor in the second step includes wet etching, dry etching and the like, and dry etching is preferably used to form a smooth surface. Dry etching includes, for example, devices such as reactive ion etching (RIE), reactive ion beam etching (RIBE), electron cyclotron etching (ECR), and ion beam etching. It can be formed by etching a nitride semiconductor. For example, a specific nitride semiconductor etching means described in Japanese Patent Application Laid-Open No. H8-17803 previously filed by the present applicant can be used. In the case where a step is formed by etching, the etched surface may have a shape in which the side surface is substantially perpendicular to the heterogeneous substrate as shown in FIG. 3, a normal mesa shape or an inverted mesa shape, or a first nitride. Semiconductor 2
Has a shape formed so that the side surface has a step shape.

In the second step, in order to control the growth of the first nitride semiconductor 2 in the vertical direction, for example, a first protective film 3 is formed on an upper flat surface of the convex portion of the concave and convex portion, and a concave portion is formed. A second protective film 4 is formed on the lower flat surface of. In the case where the side surface of the uneven portion has a step-like shape, the second protective film 4 is formed on a substantially horizontal surface on a different kind of substrate in each step of the step. The first and second protective films used in the second step have a property that a nitride semiconductor does not grow or hardly grow on the surface of the protective film. At least one of the films may be a dielectric multilayer film (reflecting mirror) having a function of reflecting light. When at least one of the first protective film and the second protective film is a dielectric multilayer film serving as a reflecting mirror, in the case of an LED, light leaking to the substrate side can be reflected on the light emitting surface, and luminous efficiency is improved. , LD, it is a good reflecting mirror of the surface emitting laser. In the case of an LED, it is preferable that the first protective film and the second protective film are reflecting mirrors, because the above-described effect is further improved. In the case of an LD, a first or second protective film is provided at a position facing the other reflecting mirror (for example, the p-electrode 27 in FIG. 8) formed on the uppermost layer of the element structure, and the protective film is at least What is necessary is just to have a reflection function. The first protective film is preferable as the protective film facing the other reflecting mirror.

As the protective film, for example, silicon oxide (SiO
_2), silicon nitride (Si _X N _Y), titanium oxide (Ti
O _2), titanium nitride (Ti _x N _y), oxides such as zirconium oxide (ZrO _2), nitrides, also include these multilayer films. When the protective film has a function of reflecting light emitted by the active layer, the material of the protective film may be a dielectric multilayer film, for example, the material for the protective film can be used. The protective film material is, for example, λ / 4n
By laminating them so that (λ: emission wavelength, n: refractive index of dielectric), a dielectric multilayer film (reflecting mirror) capable of reflecting light can be obtained. Further, as a protective film capable of reflecting light, for example, silver-white metal, such as Pt, Ni, Cr, or Ag, reflects light emitted from the active layer and has a property that nitride semiconductors are unlikely to grow on the surface. May be used. In addition, a protective film (including the case where it also has the function of a reflector)
Is the above-mentioned oxide, nitride, dielectric multilayer, metal, etc.
It is desirable to select a material having a melting point that can withstand the growth temperature of the nitride semiconductor. In the reflector made of the above material, a preferable reflector is a dielectric multilayer film of a chemically stable material which has a high reflectance of about 100% and which can withstand reaction conditions such as MOCVD. No. In order to form the protective film material on the surface of the nitride semiconductor, for example, a vapor deposition technique such as vapor deposition, sputtering, or CVD can be used.

In the second step, the first protective film 3 and the second protective film 4 are formed by etching when the method of forming the concave and convex portions on the first nitride semiconductor 2 is etching, and by dicing. The way it is formed is slightly different from that in some cases. First, in the case of forming an uneven portion by etching, after forming a protective film material to be the first protective film 3 on the first nitride semiconductor 2, a resist film is formed thereon, a pattern is transferred, exposed, and developed. After the first protection film 3 is partially formed on the first nitride semiconductor 2 by etching, the first nitride semiconductor 2 is etched to form the uneven portion. Then, the first part having the uneven portion
A protective film material to be a second protective film 4 is further formed on the nitride semiconductor 2, ie, below the first protective film 3 and the concave and convex portions, and is subjected to dry etching with CF ₄ and O ₂ gas. Is formed and only the exposed side surface of the first nitride semiconductor 2 is etched to form a second protective film 4. When formed in this way, for example, in FIG. 3, the first protective film 3 is illustrated as a single layer, but a protective film is further formed on the first protective film 3 and two protective films are laminated. It is in a state. Here, before forming the second protective film 4, the first protective film 3 formed on the upper flat surface of the uneven portion is removed, and then the protective film is formed on the upper flat surface of the convex portion and the lower flat surface of the concave portion. Alternatively, the second protective film 4 may be formed without removing the first protective film 3.

In the case where the uneven portions are formed by etching, a method of forming a protective film using a lift-off method may be performed. First, a mask having a specific shape (for example, a shape in which a protective film has a stripe shape) is formed on the surface of the first nitride semiconductor layer. Next, after forming a first protective film over the entire surface of the first nitride semiconductor on which the mask is formed, the mask is removed by a lift-off method, and the first protective film is removed.
Is formed in a specific shape. Next, the first nitride semiconductor on which the first protective film is not formed is removed by etching, so that an uneven portion is formed in the first nitride semiconductor layer. Forming a mask on the first nitride semiconductor layer on which the first protective film is formed and the uneven portion is formed,
The mask under the concave portion is removed, a second protective film is formed under the concave portion from which the mask has been removed, and a mask such as a mask on the first protective film and a mask on a side surface where the concave and convex portions are exposed are removed. I do. By doing so, the first protective film can be formed on the upper flat surface of the convex portion formed on the first nitride, and the second protective film can be formed on the lower flat surface of the concave portion.

Next, when forming an uneven portion by dicing, the first nitride semiconductor 2 is formed on the first nitride semiconductor 2 from above by a dicing saw, and then a protective film is formed thereon. Is formed, and only the protection film on the end face is etched by dry etching using CF ₄ and O ₂ gas, thereby simultaneously forming the first protection film 3 and the second protection film 4 in desired shapes and positions.

The thicknesses of the first protective film 3 and the second protective film 4 are not particularly limited, and are such that the side surfaces of the concave and convex portions can be exposed by dry etching and that the bottom surface can be covered. There is a need to. Further, the thicknesses of the first protective film 3 and the second protective film 4 are preferably adjusted so that the second nitride semiconductor 5 easily grows in the lateral direction. The thickness may be different. For example, when the first protective film 3 is formed thinner, when the second nitride semiconductor 5 grown in the third step has the same thickness as the first protective film 3, the first protective film 3 is adjacent to the first protective film 3. It is considered that the second nitride semiconductors 5 are easily joined to each other. The second protective film 4 is preferably formed relatively thick (however, the side surface of the first nitride semiconductor 2 is sufficiently exposed so that the second nitride semiconductor 5 is grown). In the initial stage of the growth of the second nitride semiconductor 5, the lower portion of the concave and convex portion (the plane of the first nitride semiconductor or the surface of the different kind of substrate) can be sufficiently covered, and the pin formed on the second protective film 4 by the heat It is considered that generation of holes can be prevented. If a pinhole is formed in the protective film, the second nitride semiconductor 5 may grow in the vertical direction from the pinhole, which is considered to cause a crystal defect.

Next, FIG. 4 is a schematic cross-sectional view in which a third step of growing the second nitride semiconductor 5 from the side surface of the first nitride semiconductor 2 exposed by etching is performed. In the third step, by forming the first protective film 3 and the second protective film 4 in the first and second steps, a portion where the second nitride semiconductor 5 can be grown is formed in the first step. Of the first nitride semiconductor 2
The second nitride semiconductor 5 starts selectively growing in the lateral direction from the side surface of the uneven portion. As the growth continues, the second nitride semiconductor 5 starts growing in the vertical direction in addition to the horizontal direction, and the second nitride semiconductor 5 grows on the protective film on which the nitride semiconductor is unlikely to grow. The nitride semiconductor 5 covers the first protective film 3 and the second protective film 4 and continues to grow. The second nitride semiconductor 5 whose growth direction has been specified in the initial stage of growth as described above has very good crystallinity with few crystal defects even when grown to a thick film.

As the second nitride semiconductor 5, the first nitride semiconductor
The same as the nitride semiconductor 2 can be used.
In the initial stage of growth, the second nitride semiconductor 5 selectively grows on the side surface of the first nitride semiconductor on which the protective film is not formed, and extends laterally from the side surface of the facing first nitride semiconductor. When the second nitride semiconductor grown in the first direction gradually grows from the horizontal direction to the vertical direction while covering the upper surface of the second protective film 4, the second nitride semiconductor grows to the same thickness as the first protective film 3.
As shown in FIG. 4, the second nitride semiconductor grows laterally toward the upper portion of the first protective film 3, and is connected with the adjacent second nitride semiconductors 5 as shown in FIG. Go.
As a result, as shown in FIG. 5, the second nitride semiconductor 5 is in a state as if grown on the first protection film 3 and the second protection film 4.

The second nitride semiconductor 5 serves as a substrate on which a nitride semiconductor having an element structure is grown.
Although the thickness of the second nitride semiconductor is not particularly limited,
00 μm to 500 μm, preferably 50 μm to 400 μm
m. Within this range, the warpage of the wafer due to the difference in thermal expansion coefficient between the heterogeneous substrate and the nitride semiconductor can be prevented, and the nitride semiconductor having the element structure can be favorably grown on the second nitride semiconductor 5 serving as the element substrate. Can be done.

In the lateral growth, when the molar ratio of the gas of the nitrogen source to the gas of the group 3 source (V / III ratio is larger than 2000), the nitride semiconductor

[0038]

[Outside 1]

The surface becomes an easily growing surface. As the growth proceeds, as shown in a schematic cross-sectional view showing the growth state of the nitride semiconductor in FIG. 6, the nitride semiconductor grows on the protective film. The crystal facet (Facet: facet) is inclined and tends to easily grow into a substantially trapezoidal shape until adjacent nitride semiconductors are joined to each other. When the V / III ratio is set to 2000 or less in the lateral growth, the nitride part semiconductor

[0040]

[Outside 2]

The surface becomes a surface that easily grows, as shown in FIG.
The facet of nitride semiconductor growing on the protective film
Tend to be almost vertical. Growing on the protective film
In comparison with the case where the cross-sectional shape of the nitride semiconductor is oblique,
Vertical defect growth is more pronounced when growing vertically
It does not reach the surface of the body and the transition is easy to bend by 90 °
It is. If the facet grows vertically,
According to surface transmission electron microscopy, it was transferred only to the upper part of the window
Was observed and almost no defects were seen on the upper part of the protective film.
You. If the facet grows vertically, the top of the window
The crystal defect concentration is about 10 ⁸Pieces / cm^TwoLess than 10
⁷Pieces / cm^TwoIn the upper part of the protective film, almost 10⁶Individual
/ Cm^TwoBelow, preferably 10^FivePieces / cm^TwoIt is as follows.
If the facets grow diagonally, the window
And 10 transitions both over the top of the overcoat⁷Pieces / cm^Twothat's all
It tends to be. The preferred value of the V / III ratio is 2
000-100, 1500-500, and in this range
If there is, it is difficult for the above crystal defects to transfer to the surface
It is easy to obtain a nitride semiconductor having good crystallinity.

In the present invention, the first nitride semiconductor 2,
And a method for growing the second nitride semiconductor 5 includes:
Although not particularly limited, nitride semiconductors such as MOVPE (metalorganic vapor phase epitaxy), HVPE (halide vapor phase epitaxy), MBE (molecular beam epitaxy), and MOCVD (metal organic chemical vapor deposition) are grown. All known methods can be applied. Preferred growth methods include:
When the film thickness is 100 μm or less, the growth rate is easily controlled by using the MOCVD method. When the film thickness is less than 100 μm, HVPE has a high growth rate and is difficult to control.

In the present invention, since a nitride semiconductor having an element structure can be formed on the second nitride semiconductor 5, the second nitride semiconductor is used in the specification as an element substrate or nitride. It may be called a semiconductor substrate.

Further, a substrate in which the main surface of the material serving as the dissimilar substrate in the first step is off-angled, or a substrate in which the main surface is off-angled in a stepwise manner can be used.
More preferred heterogeneous substrates include (0001) plane [C plane]
Is a sapphire whose main surface is sapphire, whose main surface is the (112-0) plane [A-plane], or spinel whose main surface is the (111) plane. Here, the heterogeneous substrate is (0001) plane [C
Plane), the protective film has a stripe shape perpendicular to the (112-0) plane [plane A] of the sapphire [the nitride semiconductor (101-plane)]. 0) It is preferable to form a stripe in the direction parallel to the [M-plane]]. When the sapphire has a (112-0) plane [A-plane] as a main surface, the protective film is formed of (11- 02) It is preferable to have a stripe shape perpendicular to the plane [R plane].
When the spinel is a spinel having a major surface, the protective film preferably has a stripe shape perpendicular to the (110) plane of the spinel. Here, the case where the protective film has a stripe shape is described. However, in the present invention, the nitride semiconductor easily grows in the lateral direction on the A-plane and the R-plane of sapphire and the (110) plane of the spinel. It is preferable to consider formation of a protective film in order to form an uneven portion on the first nitride semiconductor 2 so that the side surface of the first nitride semiconductor 2 is formed.

The heterogeneous substrate used in the present invention will be described in more detail with reference to the drawings. FIG. 7 is a unit cell diagram showing a crystal structure of a nitride semiconductor. Although the nitride semiconductor has a rhombohedral structure, it can be approximated in a hexagonal system. First, in the method of the present invention, a case will be described in which sapphire having a C-plane as a main surface is used, and a protective film has a stripe shape perpendicular to the sapphire A-plane. For example, FIG. 8 is a plan view of a sapphire substrate on the main surface side. In this figure, the sapphire C plane is the main surface, and the orientation flat (orientation flat) surface is the A surface. As shown in this figure, stripes of the protective film are formed in a direction perpendicular to the A-plane and parallel to each other. As shown in FIG. 8, when a nitride semiconductor is selectively grown on a sapphire C plane, the nitride semiconductor tends to grow in a direction parallel to the A plane in the plane and hardly grow in a direction perpendicular to the A plane. It is in. Therefore, when the stripes are provided in the direction perpendicular to the A-plane, the nitride semiconductors between the stripes are connected and grow easily, and the crystal growth as shown in FIGS. 2 to 5 can be easily performed. .

Next, in the case where a sapphire substrate having the main surface A is used, similarly to the case where the main surface is the C surface, for example, if the orientation flat surface is an R surface, the orientation flat surface is perpendicular to the R surface. By forming stripes parallel to each other, a nitride semiconductor tends to grow in the stripe width direction, so that a nitride semiconductor layer with few crystal defects can be grown.

Next, also for spinel (MgAl ₂ O ₄ ), the growth of the nitride semiconductor is anisotropic, and the growth surface of the nitride semiconductor is (111) plane and the orientation flat surface is (11).
When the plane is the 0) plane, the nitride semiconductor tends to grow in a direction parallel to the (110) plane. Therefore, (11
When a stripe is formed in the direction perpendicular to the 0) plane, the nitride semiconductor layer and the adjacent nitride semiconductor are connected to each other at the upper portion of the protective film, and a crystal having few crystal defects can be grown. The spinel is not shown in the figure because it is tetragonal.

Next, an element structure including a plurality of nitride semiconductor layers is formed on the second nitride semiconductor 5 (nitride semiconductor substrate) obtained in the third step to obtain a nitride semiconductor element. The fourth step will be described below. In the fourth step, on the second nitride semiconductor 5 (nitride semiconductor substrate),
A plurality of at least a plurality of n-type and p-type nitride semiconductor layers to be an element structure are grown. The nitride semiconductor having an element structure is not particularly limited as long as at least n-type and p-type nitride semiconductors are stacked. For example, an n-type nitride semiconductor having an n-type nitride semiconductor layer having a superlattice structure as an n-type nitride semiconductor layer and capable of forming an n-electrode in the n-type layer having the superlattice structure is formed. And the like. Further, any other configuration for forming the nitride semiconductor element structure, for example, the shape of the electrode and the element may be applied. Although one embodiment of the nitride semiconductor device of the present invention has been described in the embodiment, the present invention is not limited to this.

The method for growing the nitride semiconductor for forming the nitride semiconductor device structure of the present invention is not particularly limited.
VPE (metalorganic vapor phase epitaxy), HVPE (halide vapor phase epitaxy), MBE (molecular beam epitaxy), MOC
All methods known for growing nitride semiconductors, such as metal organic chemical vapor deposition (VD), can be applied. A preferred growth method is the MOCVD method, which allows the crystal to grow cleanly. However, since the MOCVD method takes time, when the film thickness is large, it is preferable to perform the method with a short time. Further, it is preferable to appropriately select various methods for growing a nitride semiconductor depending on the purpose of use and grow the nitride semiconductor.

[0050]

Embodiments of the present invention will be described below, but the present invention is not limited to these embodiments. Example 1 The nitride semiconductor substrate in Example 1 (second
Each step of manufacturing the nitride semiconductor layer 5) is described with reference to FIGS. The manufacture of the nitride semiconductor substrate in Example 1 was performed using the MOCVD method. Further, the element structure of the LED element shown in FIG. 1 is formed on the obtained nitride semiconductor substrate to obtain a nitride semiconductor element.

(Second Nitride Semiconductor Layer 5 = Manufacture of Nitride Semiconductor Substrate) A sapphire substrate 1 having a 2-inch φ, C-plane as a main surface and an orientation flat A-plane as a heterogeneous substrate 1 is placed in a reaction vessel. And a temperature of 510 ° C., using hydrogen as a carrier gas, ammonia and TMG (trimethylgallium) as a source gas, and forming a buffer layer (not shown) made of GaN on the sapphire substrate 1 to about 200 angstroms. It grows with the film thickness of.

After growing the buffer layer, only TMG is stopped,
Increase temperature to 1050 ° C. When the temperature reaches 1050 ° C., a first nitride semiconductor layer 2 made of undoped GaN is grown to a thickness of 2 μm using TMG, ammonia and silane gas as source gases (FIG. 2).

After the first nitride semiconductor layer 2 is grown, a single film of SiO ₂ and SiN is formed with a single film thickness of λ / 4 using a sputtering apparatus.
10 pairs are formed alternately so as to be n, and a dielectric multilayer film is formed as the first protective film 3. After growing the first protective film 3,
Form a striped photomask on top of it, expose,
After developing, stripe width 15μm, stripe interval 3μ
A first protective film 3 made of m (SiO ₂ / SiN) ₁₀ is formed to a thickness of 1 μm. Subsequently, the first nitride semiconductor layer 2 in a portion where the first protective film 3 is not formed is etched halfway by an RIE apparatus to form a concave and convex portion in the first nitride semiconductor layer 2. The side surfaces of the nitride semiconductor layer 2 are exposed (FIG. 3). The stripe direction is, as shown in FIG. 8, formed in a direction perpendicular to the orientation flat surface.

As shown in FIG. 4, after forming an uneven portion on the first nitride semiconductor layer 2, the surface of the first nitride semiconductor 2 having a partially recessed portion is formed on the surface of the first nitride semiconductor layer 2 in the same manner as the first protective film 3. And SiO
Forming a dielectric multilayer film consisting of ₂ and SiN, CF ₄ and O
_{The second} protective film 4 of (SiO ₂ / SiN) ₁₀ is etched by etching only the dielectric multilayer film on the side surfaces of the first nitride semiconductor 2 exposed by the formation of the concave and convex portions with the _two gases. Is formed in the lower part of the concave portion.

After forming the first protective film 3 and the second protective film 4, they are set in a reaction vessel, at a temperature of 1050 ° C., using TMG, ammonia and silane gas as raw material gases, and forming an undoped GaN. 2 nitride semiconductor layer 5 of 30 μm
m (FIGS. 4 and 5).

After the growth of the second nitride semiconductor layer 5, the wafer is taken out of the reaction vessel to obtain a nitride semiconductor substrate made of undoped GaN.

(Production Example of Comparative Nitride Semiconductor Substrate) On the other hand, for comparison, sapphire was performed in the same manner as in the above-described manufacturing method except that the first protective film 3 and the second protective film 4 were not formed in the above-described manufacturing method. After growing a buffer layer on the substrate 1, a first nitride semiconductor layer 2 was formed thereon with a thickness of 30 μm to obtain a comparative nitride semiconductor substrate.

Here, on the second nitride semiconductor layer 5 (nitride semiconductor substrate 5) and the comparative nitride semiconductor substrate manufactured as described above, arbitrarily select 9 locations in a range of 10 × 15 μm and have a unit area of The number of etch pits per unit was observed with an optical microscope, and the number of etch pits was measured. In addition,
The method of measuring the etch pit is as follows.
The N substrate is etched by about 1 μm by dry etching, and thereafter, it is observed under a microscope and the number of etch pits is counted.
The etch pits serve as an index of crystal defects. If the number of etch pits is small, it can be said that the crystals have no crystal defects and good crystallinity. As a result, the number of etch pits was 5 × 10 ⁶ / cm ² for the nitride semiconductor substrate of the present invention, and 1 × 10 ¹⁰ / cm ² for the comparative nitride semiconductor substrate. Was significantly reduced compared to the comparison.

(Formation of Element Structure) Next, on the nitride semiconductor substrate 5 obtained above, a first layer 20 of n-type Al _0.2 Ga _0.8 N doped with 1 × 10 ¹⁹ / cm ^{3 of} Si was formed. An n-side cladding layer 11 having a superlattice structure with a total film thickness of 0.4 μm is formed by alternately laminating 100 angstroms, a second layer of undoped GaN, and 20 angstroms. If the n-side cladding layer 11 is a superlattice layer, it is possible to form a cladding layer having good crystallinity and good carrier confinement without cracks.

Next, an active layer 12 of In _0.1 Ga _0.9 N having a single quantum well structure having a thickness of 20 Å and a 1 × 10 ²⁰ doped Al _0.2 Ga _0.8 layer of 0.3 μm thick Mg.
N-side p-side cladding layer 13, 0.5 μm thick Mg
To p-side contact layer 1 of 1 × 10 ²⁰ doped GaN
4 in order to grow. N-side cladding layer 1 for element structure
After the growth of the 1 to n-side contact layers 14, the wafer is taken out of the reaction vessel and annealed in a nitrogen atmosphere at 700 ° C. to reduce the resistance of the p-side cladding layer 13 and the p-side contact layer 14. Then, etching is performed from the p-layer side to expose the surface of the cladding layer 11, and an n-electrode 17 made of Ti / Al is formed with a thickness of 0.5 μm. A p-electrode 15 made of Ni / Au is formed with a thickness of 200 Å,
A pad electrode 16 for bonding is formed with a thickness of 0.5 μm on the electrode 15, and an n electrode 17 and a p electrode 15 are provided from the same surface side as shown in FIG. Finally, the sapphire substrate is polished to a thickness of about 50 μm to reduce the thickness, and then the polished surface side is scribed to be separated into chips of 350 μm square to obtain LED elements.

In the obtained LED element, a second nitride semiconductor layer having few crystal defects and good crystallinity is used as a nitride semiconductor substrate, and a protective film is provided with a reflection function at the time of lateral growth to form an active layer. Is reflected at a position close to the active layer, so that the output is 1 compared with a conventional nitride semiconductor device structure grown on a sapphire substrate and further provided with a reflecting mirror on the sapphire substrate surface. It exhibited extremely excellent characteristics of 0.5 times or more, the electrostatic withstand voltage was twice or more, and the element life was improved.

Example 2 Hereinafter, Example 2 will be described with reference to FIG. 8, which is a schematic sectional view showing the structure of a surface emitting laser device according to an embodiment of the present invention.

In the same manner as in Example 1, a buffer layer made of GaN, a first nitride semiconductor layer 2 made of undoped GaN, and a dielectric multilayer film capable of reflecting light were formed on a heterogeneous substrate 1 made of sapphire. The first protective film 3 and the second
Is formed, and a second nitride semiconductor layer 5 made of undoped GaN is sequentially stacked thereon to form a nitride semiconductor substrate 5.

On the nitride semiconductor substrate 5 formed above,
An n-side contact layer 21 made of Si-doped n-type GaN is grown to 4 μm.

Next, a barrier layer made of undoped In _0.05 Ga _0.95 N of 40 Å and a well layer made of undoped In _0.2 Ga _0.8 N of 40 Å are alternately laminated. An active layer 23 having a multiple quantum well structure (MQW) of 440 angstroms is grown. Here, the active layer is grown on the n-side contact layer as described above. However, in some cases, an n-side cladding layer may be formed on the n-side contact layer and the active layer may be grown thereon. The n-side cladding layer is not particularly limited. For example, an undoped Al _0.15 Ga _0.85 N layer having a thickness of 25 Å and a 25 Å S
i-doped GaN layers are alternately stacked to form a total film thickness of 0.4 μm.
and an n-side cladding layer composed of m superlattice layers. n
When the side cladding layer is formed of a superlattice layer, it is preferable that the n-type impurity is more doped (modulation doping) into one of the layer having a large band gap energy and the layer having a small band gap energy since the threshold tends to easily decrease.

Next, the wafer is taken out of the reaction vessel,
SiO with circular shape_TwoMask consisting of
Form. However, the position of the mask is the second protective film.
5 so as to be directly above the second protective film 5.
Formed. Here, a mask is directly applied to the active layer as described above.
Formed, but in some cases, the p-side cladding layer
And a mask may be formed thereon. p-side crack
The metal layer is not particularly limited.
Strom's undoped Al _0.15Ga_0.85N layer, 25
Angstrom Mg-doped GaN layers alternately stacked
Then, a p-side crack composed of a superlattice layer having a total film thickness of 0.4 μm is formed.
Layer 24. The p-side cladding layer is more than the superlattice layer
In this case, the p-type impurity has a large band gap energy.
Heavily doped one of the threshold layer and the smaller layer
(Modulation doping) tends to lower the threshold
preferable.

After forming the mask made of SiO ₂ ,
The wafer is transferred into a reaction vessel, and the surface of the active layer 23 where the mask is not formed is Si-doped n-type Al _0.1 Ga
_A current blocking layer 26 of _0.9 N is formed with a thickness of 0.4 μm. Note that the current blocking layer 26 may be doped with a p-type impurity such as Zn or Cd, which hardly becomes a p-type even when doped with a p-type impurity, to form a high-resistance i-type nitride semiconductor layer. When a cladding layer is provided, the Al mixed crystal ratio can be made larger than that of the cladding layer to form high-resistance i-type AlGaN.

After the formation of the current blocking layer 26, the wafer is taken out of the reaction vessel, the mask is removed, and the Mg-doped p-type G is again placed on the current blocking layer 26 in the reaction vessel.
A p-side contact layer 25 made of aN is grown.

After completion of the reaction, annealing is performed to further reduce the resistance of the p-layer. As in the first embodiment, a part of the n-side contact layer 22 is exposed by etching, and the exposed n-side contact layer 22 is made of Ti / Al. After the formation of the n-electrode 28, the p-electrode 27 of Ni / Au is formed on the surface of the p-side contact layer, and the wafer is separated into chips to obtain a surface emitting laser device having a structure as shown in FIG. Was.
As a result, an element structure is formed on the nitride semiconductor substrate 5 having few crystal defects and good crystallinity, and a protective film used for lateral growth has a light reflecting function. Since the second protective film 5 serving as a reflecting mirror is provided, a good reflecting mirror can be obtained. When the reflecting mirror is close to the active layer in this manner, the distance between the reflecting mirrors (resonator length) can be reduced, so that the internal loss of the resonator due to absorption or the like is reduced, and the oscillation threshold is lowered. Further, since the laterally grown protective film has a light reflecting function, the number of new manufacturing steps for forming the reflector is not increased, and the crystallinity of the element structure due to the formation of the reflector is not reduced. .
In the obtained surface emitting laser, a laser beam of 410 nm was observed from the sapphire substrate side.

[Example 3] In Example 1, a step is formed by dicing on the grown first nitride semiconductor layer 2 to expose an end face of the first nitride semiconductor layer 2.
As shown in FIG. 2, a nitride semiconductor substrate of the second nitride semiconductor layer 5 was obtained in the same manner except that the protective film 3 and the protective film 4 were formed. As a result of forming an element structure on the obtained nitride semiconductor substrate in the same manner as in Example 1, almost the same results as in Example 1 were obtained.

Example 4 The procedure of Example 1 was repeated, except that the first nitride semiconductor layer 2 was etched down to the sapphire substrate 1. As a result, almost the same results as in Example 1 were obtained.

[0072]

The present invention improves the luminous efficiency by forming a nitride semiconductor substrate with few crystal defects by novel lateral growth, and by giving a light reflecting function to a protective film used in the lateral growth. In addition, it is possible to provide a nitride semiconductor of a surface emitting laser device having improved performance since the LED and the protective film serve as a good reflecting mirror, and a method of manufacturing the same. Further, in the present invention, since a nitride semiconductor having a good crystallinity is used as a substrate and a nitride semiconductor constituting an element structure is grown thereon, the life time is increased, the reverse breakdown voltage is increased, and the life characteristics are improved. A nitride semiconductor device can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing one embodiment of a nitride semiconductor LED element formed on a nitride semiconductor substrate grown using a protective film having a light reflecting function in the present invention. is there.

FIG. 2 is a schematic cross-sectional view showing a structure of a nitride semiconductor wafer obtained in each step of a method for manufacturing a nitride semiconductor substrate according to the present invention.

FIG. 3 is a schematic cross-sectional view showing a structure of a nitride semiconductor wafer obtained in each step of a method for manufacturing a nitride semiconductor substrate according to the present invention.

FIG. 4 is a schematic cross-sectional view showing the structure of a nitride semiconductor wafer obtained in each step of the method for manufacturing a nitride semiconductor substrate according to the present invention.

FIG. 5 is a schematic cross-sectional view showing a structure of a nitride semiconductor wafer obtained in each step of a method for manufacturing a nitride semiconductor substrate according to the present invention.

FIG. 6 is a schematic cross-sectional view showing a structure of a nitride semiconductor wafer obtained by another embodiment of one step of the method for manufacturing a nitride semiconductor substrate according to the present invention.

FIG. 7 is a unit cell diagram showing a plane orientation of sapphire.

FIG. 8 is a plan view of a main surface of the substrate for explaining a stripe direction of a protective film.

FIG. 9 is a schematic cross-sectional view showing one embodiment of a nitride semiconductor LD device formed on a nitride semiconductor substrate grown using a protective film having a light reflecting function in the present invention. is there.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Different substrate 2 ... 1st nitride semiconductor 3 ... 1st protective film 4 ... 2nd protective film 5 ... 2nd nitride semiconductor (nitride semiconductor substrate) 11 ... n-side cladding layer 12, 23 ... active layer 13 ... p-side cladding layer 14, 25 ... p-side contact layer 15, 27 ... p electrode 16 ... pad electrode 17, 28 n-electrode 21 n-side contact layer 20 crack preventing layer 26 current blocking layer

Claims (3)

[Claims] An unevenness is formed in a first nitride semiconductor layer grown on a heterogeneous substrate made of a material different from a nitride semiconductor, and a side surface of the first nitride semiconductor layer in the uneven portion is exposed. A first protective film on an upper plane of the convex portion and a second protective film on a lower surface of the concave portion.
A nitride semiconductor element having an element structure on a second nitride semiconductor layer having fewer crystal defects than the first nitride semiconductor layer grown from the side surface of the uneven portion where the protective film is not formed, A nitride semiconductor device, wherein at least one of the first protective film and the second protective film is a reflector formed of a dielectric multilayer film. 2. A first step of growing a first nitride semiconductor layer on a heterogeneous substrate made of a material different from a nitride semiconductor, and after the first step, forming a first nitride semiconductor layer on the first nitride semiconductor layer. The first protective film on which the nitride semiconductor does not grow or hardly grows is formed on the upper flat surface of the convex portion, and the nitride is formed on the lower flat surface of the concave portion. A second step of forming a second protective film on which a semiconductor does not grow or hardly grows; and after the second step, forming a second nitride semiconductor layer from an exposed side surface of the first nitride semiconductor layer. A third step of growing a nitride semiconductor substrate, and forming an element structure including a plurality of nitride semiconductor layers on the nitride semiconductor substrate obtained in the third step to obtain a nitride semiconductor element A first protective film formed in the second step, including a fourth step; Method of manufacturing a nitride semiconductor device characterized by one of the second protective film is a reflective mirror composed of a dielectric multilayer film. 3. The method of growing a nitride semiconductor according to claim 2, wherein in the second step, a lower surface of the concave portion is a first nitride semiconductor layer surface or a heterogeneous substrate surface.