JP2000357843A - Method for growing nitride semiconductor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for growing nitride semiconductor which can obtain nitride semiconductor in which dislocation is reduced and excellent in crystallinity without using a protective film like SiO2, and a nitride semiconductor element using a substrate of the nitride semiconductor excellent in crystallinity in which dislocation is reduced. SOLUTION: In a first process, first nitride semiconductor 2 is grown on a dissimilar substrate 1 composed of material different from the nitride semiconductor. In a second process, the surface of the first nitride semiconductor 2 is partly modified in such a manner that nitride semiconductor is hard to be grown or not grown, and selectivity to the growth of nitride semiconductor is imparted to the surface of the first nitride semiconductor 2. In a third process, second nitride semiconductor 3 is grown on the first nitride semiconductor 2 which has the modified part partly on the surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a nitride semiconductor (In).
_{X Al Y Ga 1-XY N} , 0 ≦ X, 0 ≦ Y, relates to a method of growing X + Y ≦ 1), and more particularly to a method of growing substrate made fewer nitride semiconductor dislocation. Further, the present invention provides a nitride semiconductor (In _x Al _Y Ga) used for a light emitting element such as a light emitting diode or a laser diode, or a light receiving element such as a solar cell or an optical sensor using the substrate made of the nitride semiconductor.
_{The present invention} relates to a nitride semiconductor device comprising _1-XYN , 0 ≦ X, 0 ≦ Y, X + Y ≦ 1).

[0002]

2. Description of the Related Art In recent years, a nitride semiconductor has not grown or has grown on a heterogeneous substrate different from a nitride semiconductor such as sapphire, spinel or silicon carbide, or on a nitride semiconductor grown on a heterogeneous substrate. Si made of difficult material
By growing a protective film such as O ₂ and selectively growing a nitride semiconductor thereon, various nitride semiconductor growth methods [ELOG (Epitaxially laterally
y overgrown GaN) growth method] is known.

For example, as a method for growing ELOG when a protective film such as SiO ₂ is used, see Jpn. J. App
l. Phys. Vol. 37 (1998) pp. L30
In 9-L312 (hereinafter simply referred to as JJAP), a mask of SiO ₂ or the like is partially (eg, stripe-shaped) on a nitride semiconductor grown on sapphire.
It is described that a nitride semiconductor having a small number of dislocations is obtained by forming a nitride semiconductor thereon and then growing a nitride semiconductor thereon. In this ELOG growth, dislocation is hardly observed in the nitride semiconductor grown above the mask by forming a mask and intentionally growing GaN in a lateral direction so as to cover the mask. That is, when the nitride semiconductor grows in the lateral direction so as to cover the mask, dislocations also propagate in the horizontal direction with the growth of the nitride semiconductor. In the growth direction), whereby dislocations are hardly observed in the nitride semiconductor grown above the mask. The surface of GaN grown on the portion where the mask is not formed is almost 1 × 10 ⁷ /
Although there is a dislocation of cm ² , Ga grown on the upper part of the mask
Almost no dislocation is seen on the surface of N. As described above, it is possible to obtain a nitride semiconductor substrate with few dislocations, so that the life characteristics of the nitride semiconductor element can be improved.

[0004] However, in the above J.P. J. A. P. In the method of growing ELOG described in the above document, dislocations can be reduced and a device having good lifetime characteristics can be obtained, but there is a possibility that SiO ₂ is decomposed by heat during growth. When SiO ₂ is decomposed, the nitride semiconductor may grow abnormally on the SiO ₂ , or decomposed Si or O may enter the nitride semiconductor and contaminate GaN, resulting in a decrease in crystallinity.

On the other hand, as a method of growing ELOG without using a protective film such as SiO ₂ , Japanese Patent Application Laid-Open No.
No. 4791 discloses that amorphous Ga
After the N film is grown, the amorphous GaN film is etched in a stripe shape, and a nitride semiconductor is further grown on the GaN film. It is described that dislocations of a nitride semiconductor grown on a portion other than the upper portion of the amorphous film can be reduced by concentrating on a specific nitride semiconductor portion growing on the upper portion of the GaN film.

[0006]

However, in the method described in Japanese Patent Application Laid-Open No. Hei 8-64791, dislocations tend to concentrate on a specific portion growing on the upper part of the amorphous GaN film. It cannot be concentrated on the film, and the reduction of dislocations in the nitride semiconductor grown from a material other than the stripe amorphous is not sufficient. With such a growth method of ELOG without using a protective film such as SiO _2, it is not possible to obtain a nitride semiconductor with reduced dislocations to a sufficiently satisfactory degree. In order to manufacture a nitride semiconductor device having good lifetime characteristics, it is desirable to obtain a nitride semiconductor substrate with few dislocations. However, it is difficult to reduce dislocations to such an extent that the conventional method has sufficient lifetime characteristics. .

Accordingly, an object of the present invention is to provide a method of growing a nitride semiconductor capable of obtaining a nitride semiconductor having reduced dislocations and good crystallinity without using a protective film such as SiO _2. That is. Still another object of the present invention is to provide a nitride semiconductor device using a nitride semiconductor having good crystallinity and few dislocations as a substrate.

[0008]

That is, the object of the present invention is to
This can be achieved by the following configurations (1) to (11). (1) a first step of growing a first nitride semiconductor on a heterogeneous substrate made of a material different from the nitride semiconductor;
After the first step, the surface of the first nitride semiconductor is partially modified so that the nitride semiconductor hardly grows or does not grow, and the nitride on the surface of the first nitride semiconductor is A second step for providing selectivity to semiconductor growth;
A method of growing a nitride semiconductor, comprising: at least a third step of growing a second nitride semiconductor on the first nitride semiconductor having the surface partially modified after the step of . (2) after the second step includes partially forming a protective film on the first nitride semiconductor grown on the heterogeneous substrate,
Dry etching the portion where the protective film is not formed to form an N-deficient portion to partially modify the surface of the first nitride semiconductor, and then remove the protective film. The method for growing a nitride semiconductor according to the above (1), which is characterized in that: (3) The method for growing a nitride semiconductor according to (2), wherein the dry etching uses at least one of a rare gas and an O ₂ gas. (4) The second step is a step of partially diffusing impurities into the first nitride semiconductor grown on the heterogeneous substrate to partially modify the surface of the first nitride semiconductor. The method for growing a nitride semiconductor according to the above (1), wherein (5) The method for growing a nitride semiconductor according to (4), wherein the impurity is an element other than Group 3B and Group 5B of the periodic table. (6) After growing the second nitride semiconductor,
And the third step is repeated, provided that the modified portion of the surface of the second nitride semiconductor is formed above the portion other than the modified portion of the surface of the first nitride semiconductor. The method for growing a nitride semiconductor according to any one of (1) to (5), wherein (7) The method for growing a nitride semiconductor according to any one of (1) to (6), wherein the C-plane of sapphire is stepwise off-angled in the heterogeneous substrate. (8) The off-angle angle of the sapphire substrate that is off-angled in the step shape is 0.1 ° to 0.5 °, according to any one of (1) to (7). A method for growing a nitride semiconductor. (9) The direction (step direction) along the steps of the sapphire substrate that is off-angled in the step shape is formed perpendicular to the A-plane of sapphire. The method for growing a nitride semiconductor according to any one of the above items. (10) A nitride semiconductor obtained by the above-described nitride semiconductor growth method is used as a substrate, and at least an n-type nitride semiconductor, an active layer, and a p-type nitride semiconductor that form an element structure are formed thereon. A nitride semiconductor device. (11) At least an n-type nitride semiconductor, an active layer, and a p-type nitride semiconductor that form an element structure are formed on the nitride semiconductor substrate obtained by the nitride semiconductor growth method,
A nitride semiconductor laser, wherein a stripe shape or a ridge shape for guiding light of a nitride semiconductor laser element is formed on a modified portion formed on a first nitride semiconductor of a nitride semiconductor substrate. element.

In other words, the method of growing a nitride semiconductor according to the present invention comprises partially modifying the surface of the first nitride semiconductor grown on a heterogeneous substrate so that the nitride semiconductor does not grow easily. Accordingly, the second nitride semiconductor growth into the reforming portion is suppressed, the first nitride semiconductor growth into the nitride semiconductor surface occur selectivity, prior art such as SiO ₂ protective film As in the case of using the modified portion, the modified portion acts like a protective film, so that the second portion that grows above the modified portion is formed.
Almost no dislocations are seen in the nitride semiconductor.

[0010] In the conventional SiO ₂ the ELOG growth method without using, because not obtained selectivity to nitride semiconductor growth as in the case of using SiO _2, deliberately growing a nitride semiconductor laterally I can't let it. In addition, SiO
_{In the} conventional technique using ₂ , it is possible to obtain selectivity in the growth of the nitride semiconductor and to form a portion having almost no dislocation, but there is a concern that the crystallinity may be reduced due to contamination due to decomposition of SiO ₂ by heat. .

On the other hand, according to the method of growing a nitride semiconductor of the present invention, as described above, the surface of the nitride semiconductor is partially modified without using a mask such as SiO ₂ .
Selectivity can be given to the growth of the nitride semiconductor.
Thereby, the nitride semiconductor can be intentionally grown in the lateral direction toward the modified portion, and as a result, the dislocation can be reduced. In the present invention, the growth of the nitride semiconductor is suppressed in the modified portion, and the nitride semiconductor grows from portions other than the modified portion. The nitride semiconductor that started this growth,
In the process of growing into a thick film, it grows intentionally in the direction of the modified portion where the growth is suppressed, and at the same time, the dislocation also propagates in the direction of the modified portion in the lateral direction. As a result, almost no dislocation is seen in the second nitride semiconductor growing above the modified portion.

The dislocation has the property of propagating in a direction substantially similar to the growth direction of the nitride semiconductor, but promotes the lateral growth as compared with the vertical growth of the nitride semiconductor (intentionally the horizontal growth). When growing in the direction, the growth in the lateral direction tends to be promoted.). Dislocations that have once propagated in the horizontal direction tend to be less likely to propagate in the vertical direction (above the reformed portion) again, even if growth in the vertical direction is promoted, as compared to growth in the horizontal direction again. As a result, dislocations are hardly observed in the nitride semiconductor portion intentionally grown laterally on the modified portion.

When a device structure is formed using a second nitride semiconductor having a portion where dislocations are hardly observed as a substrate, a nitride semiconductor device having good life characteristics can be obtained.
In this case, it is preferable that the waveguide or the like of the element is formed above a portion where dislocation is hardly observed, from the viewpoint of improving the life characteristics.

Further, according to the present invention, in the second step, after a protective film is partially formed on the first nitride semiconductor grown on the heterogeneous substrate, a portion where the protective film is not formed is formed. To
In the step of forming the N-deficient portion by dry etching to partially modify the surface of the first nitride semiconductor and then removing the protective film, the growth of the nitride semiconductor on the modified portion is reduced. This is preferable in that the nitride semiconductor can be satisfactorily suppressed and the lateral growth of the nitride semiconductor grown from portions other than the modified portion is improved, and the dislocation is reduced. In this case, when the portion where the protective film is not formed is dry-etched, an N-deficient portion is formed, and the nitride semiconductor does not grow or hardly grows on the surface of the nitride semiconductor having the N-deficiency. Further, the present invention is preferable in that the dry etching is performed using at least one of a rare gas and an O ₂ gas, since the dry etching is performed only by sputtering and the reforming can be effectively performed. When dry etching is performed with the above-described gas on the surface of the first nitride semiconductor where the protective film is not formed, the nitride semiconductor is hardly removed, and only the quality of the nitride semiconductor changes. Therefore, the surface of the first nitride semiconductor having the modified portion is easily covered with the second nitride semiconductor.

According to the present invention, in the second step, the surface of the first nitride semiconductor is partially diffused by partially diffusing impurities into the first nitride semiconductor grown on the heterogeneous substrate. In the step of reforming, the growth of the nitride semiconductor on the modified portion can be suppressed well, the lateral growth of the nitride semiconductor grown from other than the modified portion can be improved, and the dislocation can be reduced. preferable. Further, in the present invention, when the impurity is an element other than the 3B group and 5B group of the periodic table, the growth of the nitride semiconductor in the diffusion portion of the impurity is preferably suppressed, which is preferable. In the impurity diffusion portion, the nitride semiconductor does not grow or hardly grows.

Further, in the method of modifying the surface of the first nitride semiconductor in the method of the present invention, the step of forming the second nitride semiconductor from a portion other than the modified portion does not cause much step on the surface of the first nitride semiconductor.
Tends to easily cover the modified portion. The tendency to easily cover the modified portion is that even if the second nitride semiconductor is grown relatively thin,
Since the dislocation is favorably reduced, it is preferable to repeat the second and third steps, because it is possible to simplify the operation such as shortening the growth time.

Further, in the present invention, the dislocation can be further reduced by repeating the second and third steps after growing the second nitride semiconductor into a thick film. However, the second step to be repeated is performed so that the modified portion formed on the surface of the second nitride semiconductor is located above the portion other than the modified portion formed on the surface of the first nitride semiconductor. Then, the surface of the second nitride semiconductor is partially modified. Further, the second and third steps may be repeated two or more times. As described above, when the modified portion on the surface of the first nitride semiconductor and the modified portion on the surface of the second nitride semiconductor are alternated as described above, a thick portion is formed above the modified portion. Since dislocations are hardly seen in the nitride semiconductor grown on the film, dislocations are hardly seen on the entire surface of the nitride semiconductor grown on the second nitride semiconductor having the modified portion. When a device structure is grown using a nitride semiconductor having reduced dislocations as a substrate as a whole,
This is preferable when mass-producing devices having good life characteristics.

Further, in the growth method of the present invention, if the heterogeneous substrate has a sapphire C-plane which is off-angled in a step shape, a device structure is formed using the obtained nitride semiconductor as a substrate. It is preferable because a nitride semiconductor substrate having a flat surface having a width equivalent to the size of one chip can be obtained, and an element having good life characteristics can be easily selected. Further, when the angle is turned off in a step shape, the threshold value of the laser element tends to decrease, and the light emission output of the LED tends to increase by 20 to 30%. Furthermore, in the present invention, when the off-angle of the sapphire substrate that is off-angled in a step shape is 0.1 ° to 0.5 °,
The surface property of the above-mentioned good plane portion becomes good, and it is preferable to form an element thereon to improve the life characteristics. Further, when the off angle is in the above range, the threshold value is further reduced, and the light emission output is further improved, which is preferable. Further, in the present invention, the direction (step direction) along the step of the sapphire substrate that is off-angled in a step shape is:
When formed perpendicular to the A-plane of sapphire, the second nitride semiconductor grows such that the M-plane of the nitride semiconductor is parallel to the A-plane of sapphire, and is parallel to the step direction. For example, it is preferable to form a ridge-shaped stripe because cleavage is easily performed on the M plane and a good resonance surface can be obtained.

The present invention also provides, as a substrate, a nitride semiconductor obtained by the method for growing a nitride semiconductor according to the present invention.
At least an n-type nitride semiconductor having an element structure thereon,
By forming an active layer and a p-type nitride semiconductor,
A nitride semiconductor device having good life characteristics can be obtained. Further, in the present invention, when manufacturing a nitride semiconductor laser device having a ridge-shaped stripe, the device is manufactured such that the ridge-shaped stripe is positioned above a portion modified by the nitride semiconductor growth method. Then
It is preferable because a laser element having better life characteristics can be obtained. Further, when the second and third steps are repeated by the method of the present invention, it is not necessary to particularly consider the position where the ridge-shaped stripe is formed. It is preferable to form a nitride semiconductor element in a portion where dislocations are small, since good element characteristics are obtained.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to the drawings. FIGS. 1 to 4 are schematic views showing stepwise an embodiment of the nitride semiconductor growth method of the present invention.

As an embodiment of the method for growing a nitride semiconductor according to the present invention, first, in a first step of FIG. 1, a first nitride semiconductor 2 is grown on a heterogeneous substrate 1 and a first step of FIG. In the second step, the surface of the first nitride semiconductor 2 is partially modified so that the nitride semiconductor hardly grows or does not grow, and the surface of the first nitride semiconductor 2 is In the third step of FIG. 3, a second nitride semiconductor 3 is grown on the partially modified first nitride semiconductor 2 in the third step of FIG.

Hereinafter, each of the above steps will be described in more detail with reference to the drawings. (First Step) FIG. 1 is a schematic step view showing a first step of growing a first nitride semiconductor 2 on a heterogeneous substrate 1. In the first step, as a heterogeneous substrate that can be used, for example, sapphire or spinel (MgA1) having any one of C-plane, R-plane, and 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. AlN, GaN, AlGa
N, InGaN, or the like is used. The buffer layer is 900
It is grown at a temperature of 300 ° C. or lower and a film thickness of 0.5 μm to 10 Å. When the buffer layer is formed on the heterogeneous substrate 1 at a temperature of 900 ° C. or less as described above, 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. Tends to decrease.

In the first step, as the first nitride semiconductor 2 formed on the heterogeneous substrate 1, undoped GaN, Si, G
GaN doped with n-type impurities such as e and S can be used. The first nitride semiconductor 2 has a high temperature, specifically, a temperature higher than about 900 ° C. to 1100 ° C., preferably 10 ° C.
It is grown on the heterogeneous substrate 1 at 50 ° C. When grown at such a temperature, the first nitride semiconductor 2 becomes a single crystal.
Although the thickness of the first nitride semiconductor 2 is not particularly limited,
The thickness is preferably such that the surface of the nitride semiconductor can be satisfactorily modified. For example, specifically, the thickness is preferably 500 Å to 10 μm, and more preferably 2.5 μm to 5 μm.
m is more preferred. When the content is in the above range, the warpage is prevented and the crystallinity is improved, which is preferable.

(Second Step) Next, FIG. 2 shows that after the first nitride semiconductor 2 is grown on the heterogeneous substrate 1, the surface of the first nitride semiconductor 2 is partially covered with the nitride semiconductor. FIG. 4 is a schematic cross-sectional view obtained by modifying the surface of the first nitride semiconductor 2 so that the nitride semiconductor is hardly grown or not grown, and has selectivity for growing the nitride semiconductor on the surface of the first nitride semiconductor 2.

In the second step, partially modifying the surface means that at least the surface of the first nitride semiconductor 2 is
The purpose is to suppress the growth of the nitride semiconductor by changing the surface properties of the nitride semiconductor so that the nitride semiconductor does not grow. Further, the shape of the modified portion formed on the surface of the first nitride semiconductor 2 is not particularly limited, but the shape of the first nitride semiconductor 2 when viewed from directly above is, for example,
It can be formed in a random shape, a stripe shape, a grid shape, or a dot shape. A preferred shape is a stripe shape,
This shape is preferable because it has less abnormal growth and is more buried flat.

When the shape of the modified portion is a stripe, the shape of the stripe is not particularly limited.
For example, a stripe width of the modified portion of 1 to 30 μm, preferably 10 to 20 μm, and a stripe interval of a portion other than the modified portion of 1 to 30 μm, preferably 2 to 20 μm can be formed. Having such a stripe shape is preferable in terms of reducing dislocations and improving the surface state.

In the present invention, the modification of the surface of the first nitride semiconductor 2 is not particularly limited, as long as growth of the nitride semiconductor is suppressed at least. A method in which a portion where a protective film is not formed is modified by dry etching after forming a protective film partially [however, the protective film is subjected to isotropic etching (dry etching or wet etching) after the modification. Remove (see a-1 to a-3 in FIG. 2),
And impurities (elements other than groups 3B and 5B in the periodic table)
(See b-1 to b-3 in FIG. 2). Hereinafter, these preferable reforming methods will be described.

First, a method of modifying by dry etching shown in (a-1) to (a-3) of FIG. 2 will be described. As shown in (a-1) of FIG.
Is formed partially on the surface of the nitride semiconductor 2. afterwards,
As shown in FIG. 2A-2, dry etching is performed on the first nitride semiconductor 2 on which the protective film is formed, and the surface of the first nitride semiconductor 2 where the protective film is not formed is formed. The surface of the first nitride semiconductor 2 is partially reformed by forming an N-deficient portion. After reforming, FIG.
As shown in 3), the protective film is removed by isotropic etching (dry etching or wet etching).

The protective film formed on the first nitride semiconductor 2 is not particularly limited, and protects the first nitride semiconductor when the surface of the first nitride semiconductor is modified by dry etching. The material is not particularly limited as long as the material can be used, and examples thereof include an oxide, a metal, a fluoride, and a nitride. For example, specifically, oxides and nitrides such as silicon oxide (SiO _x ), silicon nitride (Si _x N _y ), titanium oxide (TiO _x ), and zirconium oxide (ZrO _x ), and multilayer films and metals thereof Can be used. Preferred protective film materials include SiO ₂ and SiN. The use of such a protective film is preferable in terms of selective control at the time of dry etching and not diffusing into a nitride semiconductor.

As a method for forming the above protective film on the surface of the first nitride semiconductor 2, for example, a vapor deposition technique such as vapor deposition, sputtering, or CVD can be used. Further, in order to partially (selectively) form, a photomask having a predetermined shape is manufactured by using a photolithography technique, and the material is vapor-phase-formed through the photomask. A protective film having a predetermined shape can be formed. Although the shape of the protective film is not particularly limited, for example, a dot, a stripe, and a checkerboard shape can be formed,
It is preferably formed in a stripe shape so that the stripe is perpendicular to the orientation flat surface (Sapphire A surface). Further, when the surface area where the protective film is formed is smaller than the surface area of the portion where the protective film is not formed, dislocation is prevented and a nitride semiconductor substrate having good crystallinity can be obtained. The width of the protective film is adjusted by the width of the portion other than the above-mentioned modified portion, and the width between the protective films is adjusted by the width of the above-mentioned modified portion. Further, the shape on which the protective film is formed is appropriately adjusted so that the shape of the modified portion becomes, for example, a stripe shape as described above.

The dry etching for forming an N-deficient portion after the protective film is partially formed on the surface of the first nitride semiconductor 2 as described above will be described. The dry etching is anisotropic dry etching, and more preferably non-reactive dry etching. As a gas used for etching, a rare gas such as He, Ne, Ar, and Xe, and at least one gas such as an O ₂ gas can be used. Use of such a gas is preferable in that dry etching is performed only by sputtering, and the gas can be effectively reformed. The modified portion becomes N-deficient, and has a crystal face having such a property that the nitride semiconductor does not grow in this portion. Further, on the surface of the first nitride semiconductor in the portion where the protective film is not formed, when dry etching is performed with the above gas, the nitride semiconductor is hardly removed, and only the quality of the nitride semiconductor changes. Therefore, the surface of the first nitride semiconductor having the modified portion is
Is easily covered with the nitride semiconductor. After forming the modified portion as described above, the protective film is removed from the surface of the first nitride semiconductor 2, and the second nitride semiconductor 3 is grown thereon. In the present invention, the reforming portion by dry etching, the same function as SiO ₂ in the growth process of ELOG when using SiO ₂ of the prior art.

Next, a method for modifying by diffusion of impurities shown in (b-1) to (b-3) of FIG. 2 will be described. As shown in FIG. 2B-1, an element to be an impurity is partially formed on the first nitride semiconductor 2, and then, as shown in FIG. To diffuse the element near the surface of the first nitride semiconductor 2, and then
As shown in FIG. 2B-3, the element to be an impurity is
By being removed from the surface of the nitride semiconductor 2, the impurity is diffused into the portion where the element has been formed, and the surface of that portion is reformed into a crystal surface having such properties as to suppress the growth of the nitride semiconductor. .

The element serving as the impurity is not particularly limited. For example, preferable elements include elements other than the groups 3B and 5B, more preferably elements other than the groups 3B and 5B. But an element larger than Ga. More preferred specific examples include N
Any one or more of i, Au, Co, Cr, Fe and Cu can be used. When such an element is used, the diffusion to the portion other than the modified portion is small, the surface of the first nitride semiconductor 2 can be partially modified, and the dislocation of the second nitride semiconductor 3 grown after the modification can be reduced. It is preferable because it can be reduced favorably. The shape in which an element serving as an impurity is formed, the width of a portion where no element is formed, and the like are the same as the shapes of the above-described modified portion and portions other than the modified portion. The thickness of the element to be an impurity is not particularly limited as long as the surface of the first nitride semiconductor 2 is modified. For example, a preferable thickness is 10 Å to 5 μm. , Preferably 100 Å to 1 μm. A film thickness in the above range is preferable in terms of reforming the first nitride semiconductor and formation and removal of an element serving as an impurity.

The heat treatment after forming the above elements on the surface of the first nitride semiconductor 2 is performed at a temperature at which the elements are diffused, and specifically, for example, 200 to 800
C., preferably about 400 to 700 ° C., to diffuse the element into the first nitride semiconductor. Heat treatment at a temperature in the above range is preferable from the viewpoint of improving the surface of the first nitride semiconductor 2 because the element serving as an impurity is well diffused.

After the above heat treatment, the elements are removed from the surface of the first nitride semiconductor 2. As a method of removal, for example, treatment with aqua regia, hydrofluoric acid or the like is performed to remove. The element is diffused on the surface of the first nitride semiconductor 2 from which the element has been removed, and this portion becomes a crystal face having such a property as to suppress the growth of the nitride semiconductor, and is modified. ing.

(Third Step) Next, FIG. 3 shows a third step of growing the second nitride semiconductor 3 on the first nitride semiconductor 2 whose surface is partially modified. FIG. 4 is a schematic cross-sectional view performed. As the second nitride semiconductor 3, the same as the first nitride semiconductor 2 can be used. The growth temperature of the second nitride semiconductor 3 is the same as that for growing the first nitride semiconductor 2. The thickness of the second nitride semiconductor 3 is not particularly limited, but may be any thickness as long as it can cover at least the modified portion of the surface of the first nitride semiconductor 2 satisfactorily. Typically, 5
It is 30 μm, preferably 10 to 15 μm. When grown at such a film thickness, the surface of the first nitride semiconductor 2 having the modified portion can be satisfactorily covered, and a favorable second nitride semiconductor 3 with reduced dislocations can be obtained. it can.

First, the second nitride semiconductor 3 grows from the surface of the first nitride semiconductor 2 in a portion other than the modified portion,
In the process of growing, it grows laterally toward the modified portion to cover the modified portion. Then, when grown into a thick film, the modified portion has such a property that the nitride semiconductor does not grow, but as if the nitride semiconductor grew in the modified portion, as shown in FIG. The nitride semiconductor 3 grows. In addition, as shown in FIG. 4, a slight gap may be formed in the modified portion.

In growing the second nitride semiconductor 3, impurities (for example, Si, Ge, Sn, Be, Zn,
(Mn, Cr, Mg, etc.) dope, grow under reduced pressure conditions, or the molar ratio of group III and group V components (III / V molar ratio) used as a nitride semiconductor raw material
Is preferable in that the growth in the horizontal direction is promoted as compared with the growth in the vertical direction to reduce dislocations. Such reaction conditions can be applied when a nitride semiconductor is intentionally grown in the lateral direction to reduce dislocations.

In the present invention, when the second and third steps are repeated, as shown in FIG. 5, the second nitride is placed on the surface of the first nitride semiconductor 2 above the modified portion. The second nitride semiconductor is positioned so that a portion other than the modified portion that is partially formed on the surface of the semiconductor 3 is located, and above the portion other than the modified portion on the surface of the first nitride semiconductor 2. 3 so that the modified portion of the surface of the second nitride semiconductor 3 is located.
Partially modify the surface. Then, the third nitride semiconductor 4 is grown on the second nitride semiconductor 3 having the modified portion. The third nitride semiconductor 4 is preferable because the entire surface is a nitride semiconductor with few dislocations. Examples of the third nitride semiconductor 4 include those similar to the second nitride semiconductor. The thickness of the third nitride semiconductor 4 is not particularly limited, but may be any thickness as long as it can cover at least the modified portion of the second nitride semiconductor 3 well.

The second nitride semiconductor 3 serves as a substrate on which a nitride semiconductor having an element structure is grown, and the element structure is formed after removing a heterogeneous substrate in advance. In some cases, the process is performed while leaving a different substrate or the like. In some cases, the heterogeneous substrate is removed after the element structure is formed. The thickness of the second nitride semiconductor 3 when removing a heterogeneous substrate or the like is 50 μm or more, preferably 100 μm.
m, preferably 500 μm or less. When the thickness is in this range, the second nitride semiconductor 3 is less likely to be cracked even when the heterogeneous substrate, the protective film, and the like are polished and removed, so that handling is preferable.

The thickness of the second nitride semiconductor 3 in the case where a different kind of substrate or the like is left is not particularly limited.
μm or less, preferably 50 μm or less, more preferably 2 μm or less.
0 μm or less. Within this range, warpage of the wafer due to a difference in thermal expansion coefficient between the heterogeneous substrate and the nitride semiconductor can be prevented,
Furthermore, a nitride semiconductor having an element structure can be favorably grown on the second nitride semiconductor 5 serving as an element substrate.

In the method for growing a nitride semiconductor according to the present invention, the first nitride semiconductor 2 and the second nitride semiconductor 3
Although there is no particular limitation on the method of growing
OVPE (metalorganic vapor phase epitaxy), HVPE (halide vapor phase epitaxy), MBE (molecular beam epitaxy), MO
All methods known for growing nitride semiconductors, such as CVD (metal organic chemical vapor deposition), can be applied.
As a preferable growth method, when the film thickness is 50 μm or less, M
The use of the OCVD method makes it easy to control the growth rate.
When the film thickness is 50 μm or less, HVPE has a high growth rate and is difficult to control.

In the present invention, a nitride semiconductor having an element structure can be formed on the second nitride semiconductor 3.
May be referred to as an element substrate or a nitride semiconductor substrate.

Further, it is preferable to use a substrate in which the main surface of the material serving as the heterogeneous substrate in the first step is off-angled, and further a substrate whose stepped off-angle is used. When a substrate with an off-angle is used, three-dimensional growth is not observed on the surface, and step growth appears, so that the surface tends to be flat. Furthermore, when the direction (step direction) along the step of the sapphire substrate that is off-angled in a step shape is formed perpendicular to the A-plane of sapphire, the step surface of the nitride semiconductor is aligned with the cavity direction of the laser. Matches,
This is preferable because laser light is less likely to be irregularly reflected due to surface roughness.

Further preferred heterogeneous substrates include (000
1) Sapphire whose main surface is plane [C-plane], (112-0)
Sapphire whose main surface is the [A-plane] or spinel whose main surface is the (111) plane. Here, the heterogeneous substrate is (00
In the case of sapphire whose main surface is the (01) plane [C plane], the stripe shape of the modified portion formed in the first nitride semiconductor or the like is the (112-0) plane [A plane] of the sapphire.
[A stripe is formed in a direction parallel to the (101-0) [M-plane] of the nitride semiconductor], and an off-angle off angle θ (see FIG. 11) is from 0.1 ° to 0.5 °, preferably from 0.1 ° to 0.2 °. (112
−0) When the sapphire has a main surface of the [A-plane], the striped shape of the modified portion is (1) of the sapphire.
The spinel preferably has a stripe shape perpendicular to the (1-02) plane [R-plane]. When the spinel has a (111) plane as a main surface, the modified part has a stripe shape. It preferably has a stripe shape perpendicular to the (110) plane of the spinel. Here, the case where the modified portion has a stripe shape has been described. However, in the present invention, the A-plane and the R-plane of sapphire and (1)
10) Since the nitride semiconductor easily grows in the lateral direction on the surface, it is preferable to form the shape of the modified portion in consideration of these surfaces.

The heterogeneous substrate used in the present invention will be described in more detail with reference to the drawings. FIG. 6 is a unit cell diagram showing a crystal structure of sapphire, and exemplifies the following surfaces of sapphire. 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 the modified portion has a stripe shape perpendicular to the sapphire A-plane. For example, FIG. 7 is a plan view of a sapphire substrate on the main surface side. In FIG. 7, the sapphire C plane is the main plane, and the orientation flat (orientation flat) plane is the A plane. As shown in this figure, the stripes of the modified portion are formed in the direction perpendicular to the A-plane and parallel to each other. As shown in FIG. 7, 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 hard to 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 FIGS.
It is thought that the crystal growth as shown in FIG. 4 can be easily performed, but the details are not clear.

Next, when a sapphire substrate having the A surface as the main surface is used, similarly to the case where the C surface is the main 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 with respect to 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.

In the following, the direction along the step of the sapphire substrate that has been off-angled corresponds to the A of the sapphire substrate.
The case of being formed perpendicular to the plane will be described with reference to FIG. A dissimilar substrate such as sapphire that is off-angled in a step shape has a substantially horizontal terrace portion A and a step portion B as shown in FIG. The surface irregularities of the terrace portion A are small and are formed almost regularly. The step portion having such an off angle θ is desirably formed continuously over the entire substrate, but may be formed particularly partially. Note that the off angle θ indicates an angle between a straight line connecting the bottoms of a plurality of steps and the horizontal plane of the uppermost step as shown in FIG. In addition, the off-angle of the heterogeneous substrate is 0.1 ° to 0.5 °.
°, preferably 0.1 ° to 0.2 °. When the off-angle is in the above range, the surface of the first nitride semiconductor 2 has a fine streak-like morphology, and the epitaxial growth surface (the surface of the second nitride semiconductor 3) has a wavy morphology, which is obtained using this substrate. The nitride semiconductor device is smooth and has characteristics such as long life, high efficiency, high output, and improved yield.

The nitride semiconductor device of the present invention (hereinafter sometimes referred to as the device of the present invention) will be described below. The nitride semiconductor device of the present invention is formed on the second nitride semiconductor 3 (nitride semiconductor substrate) obtained by the above-described nitride semiconductor growth method of the present invention, at least of n-type and p-type having an element structure. It is formed by forming a nitride semiconductor or the like. In the present invention, when an element structure is formed on a nitride semiconductor obtained by the growth method of the present invention, a light emitting region or the like (for example, a ridge-shaped stripe in a laser element) is located above a modified portion. Forming an element structure is preferable for obtaining an element having good element characteristics such as life characteristics. The nitride semiconductor constituting the nitride semiconductor device of the present invention is not particularly limited as long as at least an n-type nitride semiconductor, an active layer, and a p-type nitride semiconductor 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. An example of the active layer is an active layer having a multiple quantum well structure containing InGaN. In addition, any other structure such as an electrode and an element shape may be applied to other structures for forming the nitride semiconductor element structure.
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.

[0053]

The present invention will be described in more detail with reference to the following examples, which are embodiments of the present invention. However, the present invention is not limited to this. [Embodiment 1] Each step in Embodiment 1 will be described with reference to FIGS. Example 1 was performed using the MOCVD method.

(First Step) A sapphire substrate 1 having a 2 inch φ, C surface as a main surface and an orientation flat surface as an A surface is set as a heterogeneous substrate 1 in a reaction vessel. Hydrogen for carrier gas, ammonia and T for source gas
A buffer layer (not shown) made of GaN on sapphire substrate 1 using MG (trimethylgallium)
Is grown to a thickness of about 200 angstroms. After growing the buffer layer, only TMG is stopped and the temperature is set to 1050 ° C.
Up to When the temperature reaches 1050 ° C, T
A first nitride semiconductor layer 2 made of undoped GaN is grown to a thickness of 2.5 μm using MG and ammonia (FIG. 1).

(Second Step) After the first nitride semiconductor layer 2 is grown, SiO ₂ is formed on the first nitride semiconductor layer 2 by a CVD apparatus, and a striped photomask is formed by photolithography. The SiO ₂ film is patterned so that the stripe width of the portion where the protective film is not formed (modified portion) is 10 μm and the stripe interval of the portion where the protective film is formed (the portion other than the modified portion) is 10 μm. A protective film is formed (a-1 in FIG. 2).
Sputtering (dry etching) with an Ar gas by an IE device to modify the surface of the first nitride semiconductor layer 2 where the protective film is not formed as N deficiency (a in FIG. 2).
-2). After the modification, the protective film is removed (FIG.
3). Then, the first portion of the portion where SiO ₂ is not formed
N deficiency occurs on the surface of the nitride semiconductor of No. 1, and the nitride semiconductor does not grow or hardly grows in this portion, and is modified (a-3 in FIG. 2). The stripe direction is formed in a direction perpendicular to the orientation flat surface as shown in FIG.

(Third Step) Next, a wafer in which the surface of the first nitride semiconductor layer 2 is partially modified is set in a reaction vessel, and TMG and ammonia are used as source gases. Then, a second nitride semiconductor layer 3 made of undoped GaN is grown to a thickness of 15 μm (FIGS. 3 and 4).

After the growth of the second nitride semiconductor layer 3, the wafer is taken out of the reaction vessel to obtain a nitride semiconductor substrate made of undoped GaN.

The obtained second nitride semiconductor layer 3 (nitride semiconductor substrate of the present invention) is replaced with CL (cathodoluminescence).
Observed by the method, the dislocation density was slightly higher in the upper part of the part other than the modified part, but there was almost no dislocation in the upper part of the modified part, indicating good crystallinity.

[Example 2] A second nitride semiconductor 3 is grown in the same manner as in Example 1, except that the second step is performed as follows. (Second step) After the first nitride semiconductor layer 2 is grown, a Ni film having a thickness of 1000 angstroms is formed so as to have a stripe width of 10 μm in the modified portion and a stripe interval of 10 μm in portions other than the modified portion. Is formed in a striped shape on the portion to be modified (b-1 in FIG. 2). Next, heat treatment is performed at 600 ° C. to diffuse Ni into the surface of the first nitride semiconductor layer 2 (b-2 in FIG. 2). Thereafter, the striped Ni is removed, and a modified surface in which Ni is diffused is formed on the surface of the first nitride semiconductor layer 2 (b-3 in FIG. 2). Ni
Nitride semiconductor 2 in a portion where is diffused as an impurity
On the surface of, the nitride semiconductor does not grow or hardly grows and is modified. The direction of the stripe is shown in FIG.
As shown in (1), it is formed in a direction perpendicular to the orientation flat surface.

When the second nitride semiconductor 3 obtained as described above was observed in the same manner as in Example 1, almost no dislocation was observed in the upper portion of the modified portion, and the same good quality as in Example 1 was observed. The result was obtained.

[Embodiment 3] The second step of Embodiment 1 and the third step are performed on the surface of the second nitride semiconductor 3 obtained in Embodiment 1.
Is repeated. (Repeated Second Step) First, as shown in FIG.
A second nitride semiconductor is provided on the surface of the first nitride semiconductor 2 above the modified portion.
The second nitride semiconductor is further formed on the surface of the first nitride semiconductor 2 other than the modified portion so that the portion other than the modified portion formed on the surface of the nitride semiconductor 3 is located. 3 so that the modified portion formed on the surface of
SiO ₂ is formed on the nitride semiconductor layer 3 by a CVD apparatus, and a stripe width of 10 μm in a portion where the protective film is not formed (modified portion) and a protective film is formed by photolithography via a striped photomask. A protective film made of a SiO ₂ film patterned at a stripe interval of 10 μm in a portion to be formed (a portion other than the modified portion) is formed, and subsequently, the protective film is sputtered (dry-etched) with an RIE apparatus using Ar gas. The surface of the portion of the second nitride semiconductor layer 3 that is not formed is modified as N-deficiency. After the modification, the protective film is removed. The removed surface of the SiO ₂ film makes it difficult for the nitride semiconductor to grow, similarly to the modified portion formed on the surface of the first nitride semiconductor of the first embodiment. (Repeated Third Step) Next, a third nitride semiconductor 4 made of undoped GaN is grown to a thickness of 15 μm on the second nitride semiconductor 3 having the modified portion (FIG. 5). .

When the third nitride semiconductor 4 obtained as described above is observed by the CL method, it is possible to obtain a nitride semiconductor with reduced dislocations as a whole.

Embodiment 4 Embodiment 4 will be described below with reference to FIG. FIG. 8 shows the second example obtained in Example 1 of the present invention.
FIG. 1 is a schematic cross-sectional view showing a structure of a laser device according to an embodiment of the present invention, in which a device structure is formed using a nitride semiconductor as a substrate. Using the second nitride semiconductor 3 obtained in Example 1 as a nitride semiconductor substrate, the following device structure is grown by lamination.

(Undoped n-type contact layer) [not shown in FIG. 8] On the nitride semiconductor substrate 1, a source gas of TM
An n-type contact layer made of undoped Al _0.05 Ga _0.95 N is grown to a thickness of 1 μm using A (trimethylaluminum), TMG, and ammonia gas.

(N-type contact layer 32) Next, at the same temperature, TMA, TMG and ammonia gas were used as source gases, silane gas (SiH ₄ ) was used as impurity gas, and S
Al _0.05 Ga _0.95 N doped with 3 × 10 ¹⁸ / cm ³ i
The n-type contact layer 2 is grown to a thickness of 3 μm.

(Crack prevention layer 33)
0 ° C and TMG, TMI (trimethyl ether)
Silane and ammonia as impurity gas
5 × 10 Si using gas ¹⁸/ Cm^ThreeDoped In
_0.08Ga_0.92The crack preventing layer 33 made of N is 0.15
It is grown to a thickness of μm.

(N-type cladding layer 34)
The temperature was raised to 50 ° C., and TMA, TMG and ammonia were used as raw material gases, and A made of undoped Al _0.14 Ga _0.86 N
A layer is grown to a thickness of 25 Å, followed by
Stop TMA and use silane gas as impurity gas.
A B layer made of GaN doped with i at 5 × 10 ¹⁸ / cm ³ is grown to a thickness of 25 Å. And
This operation is repeated 160 times to laminate the A layer and the B layer, and grow the n-type cladding layer 34 composed of a multilayer film (superlattice structure) having a total film thickness of 8000 Å.

(N-Type Guide Layer 35) Next, at the same temperature, an N-type guide layer 35 made of undoped GaN was formed to a thickness of 0.075 μm using TMG and ammonia as source gases.
It grows with the film thickness of.

(Active Layer 36) Next, the temperature was raised to 800 ° C., and TMI, TMG and ammonia were used as raw material gases.
Using silane gas as an impurity gas, Si is 5 × 10 ¹⁸
A barrier layer made of In _0.01 Ga _0.99 N doped with / cm ³ is grown to a thickness of 100 Å. Subsequently, the silane gas was stopped, and undoped In _0.11 Ga _0.89
A well layer made of N is grown to a thickness of 50 angstroms. This operation is repeated three times, and finally, an active layer 36 of a multiple quantum well structure (MQW) having a total thickness of 550 angstroms, on which a barrier layer is laminated, is grown.

(P-type electron confinement layer 37) Next, at the same temperature, TMA, TMG and ammonia are used as source gases, Cp ₂ Mg (cyclopentadienyl magnesium) is used as an impurity gas, and Mg is reduced to 1 ×. A p-type electron confinement layer 37 made of Al _0.4 Ga _0.6 N doped with 10 ¹⁹ / cm ³ is grown to a thickness of 100 Å.

(P-type guide layer 38) Next, the temperature was set to 105
0 ° C, using TMG and ammonia as raw material gas,
0.07 p-type guide layer 8 made of undoped GaN
It is grown to a thickness of 5 μm. This p-type guide layer 8 is grown as undoped, but the p-type electron confinement layer 37 is formed.
Mg concentration from 5 × 10 ¹⁶ / cm
³ indicates p-type.

(P-type cladding layer 39) Next, at the same temperature, TMA, TMG and ammonia were used
An A layer made of undoped Al _0.1 Ga _0.9 N is grown to a thickness of 25 Å, followed by stopping TMA, using Cp ₂ Mg as an impurity gas, and adding 5 × 1 Mg.
A B layer of GaN doped with 0 ¹⁸ / cm ³ is grown to a thickness of 25 Å. This operation is repeated 100 times to laminate the A layer and the B layer, thereby growing a p-type cladding layer 39 of a multilayer film (superlattice structure) having a total film thickness of 5000 Å.

(P-type contact layer 40) Next, at the same temperature, TMG and ammonia are used as source gases, Cp ₂ Mg is used as an impurity gas, and Mg is 1 × 10 ²⁰ / cm ^3.
The p-type contact layer 40 made of doped GaN is
It is grown to a thickness of 0 Å.

After the completion of the reaction, the wafer is annealed at 700 ° C. in a nitrogen atmosphere in a reaction vessel to further reduce the resistance of the p-type layer. After annealing, the wafer is taken out of the reaction vessel, a protective film made of SiO ₂ is formed on the surface of the uppermost p-side contact layer, and is etched by SiCl ₄ gas using RIE (reactive ion etching). As shown, the surface of the n-side contact layer 32 where the n-electrode is to be formed is exposed. Next, as shown in FIG. 9A, almost all of the uppermost p-side contact layer 40 is covered with a Si oxide (mainly SiO 2) by a PVD apparatus.
₂ ) After forming a first protective film 61 of 0.5 μm in thickness, a mask of a predetermined shape is applied on the first protective film 61 to form a third protective film 63 of photoresist. ,
It is formed with a stripe width of 1.8 μm and a thickness of 1 μm. Next, as shown in FIG. 9B, after forming the third protective film 63,
CF ₄ by RIE (Reactive Ion Etching)
The first protective film is etched into a stripe shape by using gas and using the third protective film 63 as a mask. Thereafter, the first protective film 61 having a stripe width of 1.8 μm can be formed on the p-side contact layer 40 as shown in FIG.

Further, as shown in FIG. 9D, after the first protection film 61 in the form of a stripe is formed, S is formed again by RIE.
The p-side contact layer 40 and the p-side cladding layer 39 are etched using iCl ₄ gas to form a ridge-shaped stripe having a stripe width of 1.8 μm. However, as shown in FIG. 8, the ridge-shaped stripe is formed so as to be located above the concave portion formed in the first nitride semiconductor. After the formation of the ridge stripe, the wafer is transferred to a PVD apparatus, and a second protective film 62 made of Zr oxide (mainly ZrO ₂ ) is placed on the first protective film 61 as shown in FIG. Then, a film having a thickness of 0.5 μm is continuously formed on the p-side cladding layer 39 exposed by the etching. The formation of the Zr oxide in this way is preferable because the pn plane is insulated and the transverse mode can be stabilized. Next, the wafer is immersed in hydrofluoric acid, and as shown in FIG. 9F, the first protective film 61 is removed by a lift-off method.

Next, as shown in FIG. 9 (g), the first protective film 61 on the p-side contact layer 40 is removed and the exposed surface of the p-side contact layer is made of Ni / Au.
An electrode 20 is formed. However, the p-electrode 20 has a stripe width of 100 μm and is formed over the second protective film 62 as shown in FIG. After forming the second protective film 62,
As shown in FIG. 8, on the exposed surface of the n-side contact layer 2, an n-electrode 21 made of Ti / Al is formed in a direction parallel to the stripe.

As described above, the sapphire substrate of the wafer on which the n-electrode and the p-electrode have been formed is polished to 70 μm, and then cleaved in a bar shape from the substrate side in a direction perpendicular to the stripe-shaped electrodes. A resonator is formed on a cleavage plane (11-00 plane, a plane corresponding to the side surface of a hexagonal columnar crystal = M plane).
A dielectric multilayer film made of SiO ₂ and TiO ₂ is formed on the cavity surface, and finally, the bar is cut in a direction parallel to the p-electrode to obtain a laser device as shown in FIG. The resonator length is 30
It is desirable to set it to 0 to 500 μm. The obtained laser element was set on a heat sink, and the respective electrodes were wire-bonded, and laser oscillation was attempted at room temperature. As a result, continuous oscillation at an oscillation wavelength of 400 nm was confirmed at room temperature with a threshold value of 2.5 kA / cm ² and a threshold voltage of 5 V, and a lifetime of 10,000 hours or more was shown at room temperature. Further, since the surface state of the second nitride semiconductor is good, a laser device having good device characteristics can be obtained with high yield.

Embodiment 5 Hereinafter, Embodiment 5 will be described with reference to FIG.
Will be described. FIG. 10 is a schematic cross-sectional view showing the structure of a laser device according to one embodiment using a nitride semiconductor layer obtained by the growth method of the present invention as a substrate.

In the first embodiment, the second nitride semiconductor 3
When growing Si, 1 × 10 ¹⁸/ Cm^ThreeDope
In the same manner, except that the film thickness is 150 μm,
A second nitride semiconductor 3 is obtained. The size of the obtained wafer
The fire substrate and the like are polished and removed, and the second nitride semiconductor 3 is removed.
As a simple substance.

Next, the second nitride semiconductor layer 3 (Si-doped GaN) on the surface opposite to the surface from which the sapphire substrate has been removed
Is set in the reaction vessel of the MOVPE apparatus, and the following layers are formed on the second nitride semiconductor layer 3.

(N-side cladding layer 43) Next, Si was added to 1 ×
A first layer of 10 ¹⁹ / cm ³ doped n-type Al _0.2 Ga _0.8 N, 20 Å, and undoped
A superlattice structure having a total film thickness of 0.4 μm is formed by alternately laminating 100 second layers composed of GaN of pe) and 20 angstroms.

(N-side light guide layer 44) Subsequently, 1
An n-type light guide layer 44 of x10 ¹⁷ / cm ³ doped n-type GaN is grown to a thickness of 0.1 μm.

(Active Layer 45) Then, Si was added to 1 × 10 ¹⁷ /
A well layer of In _0.2 Ga _0.8 N doped with cm ³ , 25 Å, and I × 10 ¹⁷ / cm ³ doped with Si
An active layer 45 having a multiple quantum well structure (MQW) having a total film thickness of 175 Å is formed by alternately laminating barrier layers of n _0.01 Ga _0.95 N and 50 Å.

(P-side Cap Layer 46) Next, p-type Al _0.3 doped with Mg at 1 × 10 ²⁰ / cm ³ , having a band gap energy larger than that of the p-side light guide layer 47 and larger than that of the active layer 45. A p-side cap layer 46 of Ga _0.9 N is grown to a thickness of 300 Å.

(P-side light guide layer 47) Next, Mg band gap energy is smaller than that of the p-side cap layer 46.
Is grown at a film thickness of 0.1 μm by p-type GaN doped with 1 × 10 ¹⁸ / cm ³ .

(P-side cladding layer 48) Next, Mg was added to 1 ×
A first layer of p-type Al _0.2 Ga _0.8 N doped with 10 ²⁰ / cm ³ , 20 Å, and 1 × 10 ²⁰ Mg;
/ Cm ³ doped second layer of p-type GaN, 20 angstrom alternately laminated to a total film thickness of 0.4 μm
A p-side cladding layer 48 of m superlattice layers is formed.

(P-side contact layer 49) Finally, a p-side contact layer 49 made of p-type GaN doped with Mg at 2 × 10 ²⁰ / cm ³ is grown to a thickness of 150 Å.

After completion of the reaction, the wafer is annealed in a nitrogen atmosphere at 700 ° C.
The resistance of the mold layer is further reduced. After annealing, the wafer is taken out of the reaction vessel and, as shown in FIG.
The uppermost p-type contact layer 49 and the p-type cladding layer 48 are etched by a device to form a ridge shape having a stripe width of 4 μm, and Ni / A is formed on the entire surface of the ridge surface.
A p electrode 51 made of u is formed.

Next, as shown in FIG. 10, the surface of the p-side cladding layer 48 and the contact layer 49 excluding the p-electrode 51 is
An insulating film 50 made of O ₂ is formed, and a p pad electrode 52 electrically connected to the p electrode 51 via the insulating film 50 is formed.

After the formation of the p-side electrode, the second nitride semiconductor layer 3
Ti / Al over the entire surface on which the element structure of
An n-electrode 53 is formed with a thickness of 0.5 μm, and Au / S is formed thereon for metallization with a heat sink.
A thin film made of n is formed.

Then, scribe from the n-electrode side 53,
The second nitride semiconductor layer 5 is cleaved at the M-plane (11-00, a surface corresponding to the side surface of the hexagonal prism in FIG. 6) of the second nitride semiconductor layer 3, thereby forming a resonance surface. A dielectric multilayer film composed of SiO ₂ and TiO ₂ was formed on both or one of the resonance surfaces, and finally, the bar was cut in a direction parallel to the p-electrode to form a laser chip. Next, the chip is mounted on the heat sink face up (in a state where the substrate and the heat sink are opposed to each other), and the p-pad electrode 52 is wire-bonded.
When laser oscillation was attempted at room temperature, continuous oscillation at an oscillation wavelength of 405 nm was confirmed at room temperature at a threshold current density of 2.5 kA / cm ² and a threshold voltage of 4.5 V, indicating a lifetime of 10,000 hours or more.

Example 6 Using the third nitride semiconductor 4 obtained in Example 3 as a substrate, an element structure similar to that of Example 4 was formed to manufacture a laser element. The obtained laser element has good life characteristics as in Example 4. In addition, good characteristics are exhibited even if the ridge-shaped stripe is formed at the upper portion of the second nitride semiconductor 3 other than the modified portion regardless of the upper portion of the modified portion.

[Embodiment 7] In the embodiment 1, as the sapphire substrate 1, 2 inches φ, off-angle θ = 0.
2 °, a step (height) of about 1 atomic layer, a terrace width W having steps of about 40 angstroms, a C-plane as a main surface, an orientation flat surface as an A-plane, a direction along the steps,
That is, the second nitride semiconductor 3 is grown in the same manner except that a sapphire substrate provided with the direction of the step perpendicular to the A-plane is used. Using the obtained second nitride semiconductor 3 as a substrate, an element structure similar to that of Example 4 is formed to manufacture a laser element. The obtained laser device has a lower threshold than that of Example 4, and has better life characteristics.

[0094]

As described above, according to the present invention, the surface of the nitride semiconductor is partially modified so that the modified portion is substantially similar to SiO ₂ used in the conventional ELOG growth. Intentionally promote lateral growth of nitride semiconductors,
Thus, it is possible to provide a nitride semiconductor growth method capable of obtaining a nitride semiconductor with reduced dislocation and good crystallinity. Further, the present invention can provide a nitride semiconductor element having good crystallinity and good lifetime characteristics using a nitride semiconductor with few dislocations as a substrate.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a structure of a nitride semiconductor wafer obtained in each step of the method of the present invention.

FIG. 2 is a schematic sectional view showing a structure of a nitride semiconductor wafer obtained in each step of the method of the present invention.

FIG. 3 is a schematic sectional view showing a structure of a nitride semiconductor wafer obtained in each step of the method of the present invention.

FIG. 4 is a schematic sectional view showing a structure of a nitride semiconductor wafer obtained in each step of the method of the present invention.

FIG. 5 is a schematic sectional view showing a structure of a nitride semiconductor wafer obtained in each step of the method of the present invention.

FIG. 6 is a unit cell diagram showing a plane orientation of sapphire.

FIG. 7 is a plan view of the main surface of the substrate for explaining the stripe direction of the protective film.

FIG. 8 is a schematic sectional view showing one structure of a nitride semiconductor LD device using a substrate according to the method of the present invention.

FIG. 9 is a schematic cross-sectional view showing a partial structure of a wafer in each step of a method according to an embodiment for forming a ridge-shaped stripe.

FIG. 10 is a schematic sectional view showing one structure of a nitride semiconductor LD device using a substrate according to the method of the present invention.

FIG. 11 is a schematic cross-sectional view showing an enlarged part of a substrate according to the method of the present invention.

[Explanation of symbols]

 Reference numeral 1 denotes a heterogeneous substrate 2 denotes a first nitride semiconductor 3 denotes a second nitride semiconductor 4 denotes a third nitride semiconductor

Continued on front page F-term (reference) 5F041 CA21 CA46 CA49 CA61 CA74 5F045 AA04 AB09 AB14 AB17 AB18 AB32 AB33 AC01 AC08 AC11 AC12 AC19 AD07 AD08 AD09 AD10 AD11 AD12 AD13 AD14 AD15 AF02 AF03 AF04 AF06 AF09 AF13 AF20 BB12 CA10 DA55 HA13 HA14 HA16 HA20 5F073 AA13 AA74 CA17 CB05 CB07 DA05 DA24 EA29

Claims (11)

[Claims] 1. A first step of growing a first nitride semiconductor on a heterogeneous substrate made of a material different from a nitride semiconductor, and after the first step, a surface of the first nitride semiconductor A second step of partially modifying the nitride semiconductor so that it hardly grows or does not grow so that the nitride semiconductor has selectivity on the growth of the nitride semiconductor on the surface of the first nitride semiconductor; After the second step, at least a third step of growing a second nitride semiconductor on the first nitride semiconductor whose surface is partially modified is provided. Growth method. 2. The method according to claim 2, wherein in the second step, after a protection film is partially formed on the first nitride semiconductor grown on the heterogeneous substrate, a portion where the protection film is not formed is removed by dry etching. The nitride semiconductor according to claim 1, wherein the step of forming the N-deficient portion by etching to partially modify the surface of the first nitride semiconductor, and thereafter removing the protective film. Growth method. 3. The dry etching is performed by using a rare gas and O
_{3. The} method for growing a nitride semiconductor according to claim 2, wherein at least one of _two gases is used. 4. The step of partially modifying a surface of the first nitride semiconductor by partially diffusing an impurity into the first nitride semiconductor grown on the heterogeneous substrate. 2. The method for growing a nitride semiconductor according to claim 1, wherein 5. The method according to claim 1, wherein the impurities are a 3B group or a 5B group of the periodic table.
The method for growing a nitride semiconductor according to claim 4, wherein the nitride semiconductor is an element other than Group B. 6. The step of repeating the second and third steps after growing the second nitride semiconductor, provided that the portion of the surface of the second nitride semiconductor that is modified is the first nitride semiconductor. The method for growing a nitride semiconductor according to any one of claims 1 to 5, wherein the nitride semiconductor is formed on a portion other than a modified portion on the surface of the nitride semiconductor. 7. The method for growing a nitride semiconductor according to claim 1, wherein the heterogeneous substrate has a C-plane of sapphire that is stepped off-angle. 8. An off-angle angle of the sapphire substrate which is off-angled in a step shape is 0.1 ° to 0.1 °.
The method for growing a nitride semiconductor according to claim 1, wherein the angle is 5 °. 9. A direction (step direction) along a step of the sapphire substrate that is off-angled in a step shape.
Is formed perpendicular to the A-plane of sapphire. The method for growing a nitride semiconductor according to claim 1, wherein 10. A nitride semiconductor obtained by the method for growing a nitride semiconductor is used as a substrate, and at least an n-type nitride semiconductor, an active layer, and a p-type nitride semiconductor having an element structure are formed thereon. A nitride semiconductor device characterized by the above-mentioned. 11. A nitride semiconductor substrate obtained by the method for growing a nitride semiconductor, wherein at least n
The nitride semiconductor laser, the active layer, and the p-type nitride semiconductor are formed, and the light of the nitride semiconductor laser device is guided above the modified portion formed on the first nitride semiconductor of the nitride semiconductor substrate. A nitride semiconductor laser device formed by forming a stripe shape or a ridge shape.