JP2009238803A - Gan-based semiconductor substrate, method of manufacturing the same, and semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a large diameter GaN-based semiconductor substrate with little threading dislocation, and to provide method of manufacturing the same. <P>SOLUTION: A GaN template substrate 10 includes a ZnO single crystal substrate 11, a protective film 12 formed on the backside 11a and the side surface 11b of the substrate 11, an interface layer 13 formed on the surface 11c of the ZnO single crystal substrate 11, an InGaN layer 14 which is formed on the interface layer and lattice-matched with the ZnO single crystal substrate 11, and a GaN layer 15 as thick as several μm formed on the InGaN layer. The GaN layer 15 is grown to overlie an InGaN/ZnO compound substrate having the InGaN layer 14 which is grown while lattice matching with the ZnO single crystal substrate 11 having a small dislocation density, thereby the threading dislocation of the GaN layer 15 is reduced sharply. When the GaN layer 15 is grown, the protective film 12 prevents the ZnO single crystal substrate 11 from being destroyed by ammonia, and mixing of Zn or O to the InGaN layer or the GaN layer can be controlled. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a GaN-based semiconductor substrate suitable for manufacturing a light-emitting element, particularly a semiconductor laser diode, a manufacturing method thereof, and a semiconductor element.

  Conventionally, a blue-violet laser diode uses a self-standing GaN substrate grown by a method such as HVPE, and a nitride semiconductor laminate in which each layer such as an active layer, a clad layer, and a contact layer is epitaxially grown on this substrate by a method such as MOCVD. Formed by processing the body.

Conventionally, a method of growing a self-standing GaN substrate by growing a GaN layer on the GaAs substrate and removing the GaAs substrate has been used (see Patent Documents 1, 2, and 3).
WO99 / 23693 JP 2001-102307 A JP 2000-340509 A

Meanwhile, in the process leading to the practical use of blue-violet laser diodes and the like, it has been important to reduce the dislocation density of the substrate in order to ensure reliability. According to the prior art disclosed in Patent Documents 1 to 3, a self-standing GaN substrate with a reduced threading dislocation density is realized. However, in order to ensure higher reliability, it is necessary to further reduce the density of crystal defects typified by threading dislocations.
An object of the present invention is to provide a GaN-based semiconductor substrate having a better crystal quality than before, a method for manufacturing the same, and a semiconductor element.

  In order to solve the above-mentioned problem, a GaN-based semiconductor substrate according to claim 1 includes a ZnO substrate, a protective film formed on one side and a side surface of the ZnO substrate, and the other of the ZnO substrate. A GaN template substrate comprising: an interface layer formed on a surface; an InGaN layer lattice-matched to the ZnO substrate formed on the interface layer; and a GaN layer of at least 2 μm or more formed on the InGaN layer It is characterized by being.

  According to this configuration, a large single crystal, specifically, a ZnO substrate capable of manufacturing a substrate having a size of 2 to 3 inches or more is used as the base substrate. A template board can be made. Since the GaN layer is grown on the basis of an InGaN / ZnO composite substrate having an InGaN layer grown by lattice matching with a ZnO substrate originally having a low dislocation density, the threading dislocation density of the GaN layer is greatly reduced. Further, the protective film formed on one side and the side surface of the ZnO substrate can suppress the destruction of the ZnO substrate by ammonia, which is one of GaN source gases, when the GaN layer is grown. Introducing Zn and O into the InGaN layer and the GaN layer can be suppressed. Therefore, it is possible to obtain a GaN template substrate having a GaN layer having a good crystal quality with reduced threading dislocations as compared with the prior art.

The GaN-based semiconductor substrate according to a second aspect of the invention is characterized in that the interface layer is composed of a GaN layer having a critical thickness or less, an InN layer, and a composite layer combining these.
According to a third aspect of the present invention, there is provided a method for manufacturing a GaN-based semiconductor substrate, comprising: a first step of forming a protective film on one surface and side surface of a ZnO substrate; and forming an interface layer on the other surface of the ZnO substrate. A second step of forming a third step of forming an InGaN layer lattice-matched to the ZnO substrate on the interface layer, a fourth step of forming a GaN layer of at least 2 μm or more on the InGaN layer, To produce a GaN template substrate.
According to this configuration, it is possible to manufacture a GaN template substrate having a GaN layer with good crystal quality and having fewer threading dislocations than before.

  According to a fourth aspect of the present invention, there is provided a method of manufacturing a GaN-based semiconductor substrate, further comprising a fifth step of manufacturing a self-standing GaN substrate by removing the protective film and the ZnO substrate.

According to this configuration, it is possible to obtain a self-standing GaN substrate having a GaN layer having a good crystal quality with fewer threading dislocations than in the past.
The method for manufacturing a GaN-based semiconductor substrate according to claim 5 is to remove a part of the protective film, the ZnO substrate, the interface layer, the InGaN layer, and the GaN layer that forms an interface with the InGaN layer. The semiconductor device further includes a sixth step of manufacturing a self-standing GaN substrate.

  According to this configuration, it is possible to obtain a self-standing GaN substrate having a GaN layer with better crystal quality with reduced threading dislocations. A semiconductor element according to a sixth aspect of the invention is characterized in that a semiconductor element structure is formed on the self-standing GaN substrate according to the fourth or fifth aspect.

  According to this configuration, by forming an element structure on a free-standing GaN substrate, a semiconductor light emitting element such as a semiconductor laser element or a light emitting diode, or a semiconductor element such as a power Schottky diode or a field effect transistor (FET) is formed. it can.

  According to a seventh aspect of the present invention, in the semiconductor device according to the seventh aspect, the semiconductor device structure includes a first conductivity type AlGaN clad layer formed on the free-standing GaN substrate, and an InGaN active layer formed on the AlGaN clad layer. Alternatively, an active layer having a quantum well structure made of GaN, a second conductivity type AlGaN cladding layer formed on the active layer, and a second conductivity type GaN contact layer formed on the AlGaN cladding layer, And a semiconductor light emitting device.

According to this configuration, a semiconductor light emitting element having a blue emission wavelength can be realized.
A GaN-based semiconductor substrate according to claim 8 includes a ZnO substrate, a protective film formed on one surface and side surfaces of the ZnO substrate, and an interface layer formed on the other surface of the ZnO substrate, An InGaN template substrate comprising: an InGaN layer lattice-matched with the ZnO substrate formed on the interface layer; and an InGaN layer of at least 2 μm or more formed on the InGaN layer. According to this configuration, a good quality thick InGaN layer doped with In can be grown on the ZnO substrate, so that an InGaN template substrate having a lower threading dislocation density than the conventional one can be obtained. It is possible to obtain a substrate in which the lattice constant, which is advantageous for increasing the oscillation wavelength, is adjusted.

  The method for manufacturing a GaN-based semiconductor substrate according to claim 9 includes a first step of forming a protective film on one surface and side surface of the ZnO substrate, and an interface layer grown on the other surface of the ZnO substrate. A second step of forming an InGaN layer lattice-matched to the ZnO substrate on the interface layer, and a fourth step of forming an InGaN layer of at least 2 μm or more on the InGaN layer. And an InGaN template substrate is manufactured by performing the steps.

  The method for manufacturing a GaN-based semiconductor substrate according to claim 10 further includes a fifth step of fabricating a self-supporting InGaN substrate by removing the protective film and the ZnO substrate.

  A method of manufacturing a GaN-based semiconductor substrate according to an eleventh aspect includes: the protective film of the InGaN template substrate; the ZnO substrate; the interface layer; and a part of the InGaN layer that forms an interface with the interface layer. It is characterized by further comprising a sixth step of producing a free-standing InGaN substrate by removing. A semiconductor device according to a twelfth aspect of the invention is characterized in that a semiconductor device structure is formed on the self-standing InGaN substrate of the tenth or eleventh aspect.

  According to this configuration, by forming a semiconductor element structure on a free-standing InGaN substrate, a semiconductor light emitting element such as a semiconductor laser element or a light emitting diode, or a semiconductor element such as a power Schottky diode or a field effect transistor (FET) can be obtained. Can be formed.

  According to a thirteenth aspect of the present invention, there is provided the semiconductor device according to the first aspect, wherein the semiconductor device structure has a first conductivity type AlInGaN clad layer formed on the freestanding InGaN substrate and an InGaN active layer formed on the AlInGaN clad layer. Alternatively, an active layer having a multiple quantum well structure made of GaN, a second conductivity type AlInGaN cladding layer formed on the active layer, and a second conductivity type InGaN contact layer formed on the AlInGaN cladding layer, And is configured as a semiconductor light emitting device.

  According to this configuration, it is possible to realize a semiconductor light emitting element that emits light in a visible light region from blue to red, in particular, visible light having a longer wavelength than blue (for example, green).

  According to the present invention, it is possible to realize a GaN-based semiconductor substrate and a semiconductor element having better crystal quality than conventional ones.

Hereinafter, embodiments embodying the present invention will be described with reference to the drawings. In the description of each embodiment, similar parts are denoted by the same reference numerals, and redundant description is omitted.
(First embodiment)
FIG. 1 shows a GaN template substrate 10 according to the first embodiment of the present invention.

  The GaN template substrate 10 as a GaN-based semiconductor substrate is used as an epitaxial growth substrate (epitaxial wafer) for a blue-violet semiconductor laser device having an oscillation wavelength near 405 nm as an example of a semiconductor device.

  The GaN template substrate 10 includes a ZnO single crystal substrate (ZnO substrate) 11, a protective film 12 formed on the back surface (one surface) 11 a and the side surface 11 b of the ZnO single crystal substrate 11, and the surface of the ZnO single crystal substrate 11. (The other side) interface layer 13 formed on 11c, InGaN layer 14 lattice-matched with ZnO single crystal substrate 11 formed on thin interface layer 13, and at least 2 μm or more formed on InGaN layer 14 And a thick GaN layer 15.

  The ZnO single crystal substrate 11 is used by slicing an ingot grown by a method such as hydrothermal synthesis. The principal plane orientation is the c plane, which is an oxygen plane or a Zn plane. A slight off angle of about 1 degree may be provided. At least the main surface of the ZnO single crystal substrate 11 on which the epitaxial layer is arranged is flattened to the atomic level by chemical mechanical polishing and heat treatment. A ZnO-based epitaxial layer may be disposed on the ZnO single crystal substrate 11.

The interface layer 13 is a pseudo-lattice matching interface layer obtained by combining InN and GaN monolayers. Typically, a structure in which a combination of a five-molecular GaN layer and a single-molecular InN layer is used as a structural unit and this is repeated one to ten times is used. As the interface layer is elastically distorted, the GaN layer can be made as thin as about 3 molecular layers or as thick as about 10 molecular layers within a range in which pseudo lattice matching can be maintained. Layers or less are preferred. Moreover, the numerical value of the molecular layer here does not necessarily need to be an integer. The thus configured pseudo-lattice matching interface layer has a thickness of about 2 to 50 nm, and the interface layer is grown on the ZnO single crystal substrate and the ZnO single crystal substrate 11 while inheriting the lattice constant of the ZnO single crystal substrate 11. Interdiffusion due to constituent elements with the InGaN layer can be prevented.

  The In composition of the InGaN layer 14 lattice-matched with the ZnO single crystal substrate 11 formed on the ZnO single crystal substrate 11 through the thin interface layer 13 is about 0.15, but grows to such an extent that crystal defects are not increased. The possible In composition is 0.1 to 0.2. Strictly speaking, the InN composition of the InGaN layer 14 is adjusted so that the half-value width of the diffraction peak of the rocking curve observed by the X-ray diffraction method is minimized. The thickness of the InGaN layer 14 is typically 0.1 μm. If the thickness is 0.01 μm or less, mutual diffusion may increase when the GaN layer 15 is grown, which is not preferable.

  In addition, the InGaN layer 14 grows to be a group III surface regardless of whether the oxygen surface or the Zn surface of the ZnO single crystal substrate 11 is used. When the growth temperature is extremely low, the N surface may be formed.

  The GaN layer 15 formed on the InGaN layer 14 has a thickness of at least 2 μm or more in order to improve the crystal quality. In order to partially remove the ZnO substrate at the stage of device fabrication, it is desirable to have a thickness of 10 μm or more. Furthermore, in order to make a self-supporting substrate, a thickness of about 50 μm or more is necessary to maintain mechanical strength, and it is typically desirable that the thickness be about 200 μm. However, in order to maintain the mechanical strength of the self-supporting substrate, it is possible to use a self-supporting substrate of about 50 μm or less when it is used by being attached to another ZnO substrate or GaAs substrate.

The GaN layer 15 may be highly undoped, but may be p-type doped with p-type impurities such as Mg, or may be n-type doped with n-type impurities such as Si.
The protective film 12 formed on the back surface 11 a and the side surface 11 b of the ZnO single crystal substrate 11 is a protective film for suppressing deterioration of the ZnO single crystal substrate 11 when the GaN layer 15 is grown. That is, the protective film 12 can suppress the destruction of the ZnO single crystal substrate 11 due to the reaction with ammonia, which is a raw material gas used when the GaN layer 15 is grown. The protective film 12 can be a film formed by sputtering a refractory metal such as Mo or a dielectric film made of SiN or the like, but a GaN layer may be used. (Method for manufacturing GaN template substrate)

Next, a method for manufacturing the GaN template substrate 10 shown in FIG. 1 will be described.
The manufacturing method of the GaN template substrate 10 includes the following steps.
1. A step of forming a protective film 12 on the back surface 11a and the side surface 11b of the ZnO single crystal substrate 11.
2. A step of growing and forming the interface layer 13 on the surface 11c of the ZnO single crystal substrate 11.
3. A step of forming an InGaN layer 14 lattice-matched with the ZnO single crystal substrate 11 on the interface layer 13.
4. A step of forming a thick GaN layer 15 on the InGaN layer 14.
By performing these steps, the GaN template substrate 10 is completed.

A method for manufacturing such a GaN template substrate 10 will be described in more detail below.
(Step 1) First, a ZnO single crystal substrate 11 having a (000_1) plane (-c plane: oxygen plane) as a substrate plane (surface) is prepared. A (0001) plane (+ c plane: Zn plane) may be used. An off angle of about 1 degree may be applied.

(Step 2) A protective film 40 made of a nitride semiconductor (InGaN, AlInN, AlGaInN, etc.) is formed on the back surface 11a and both side surfaces 11b of the outer surface of the ZnO single crystal substrate 11 by MBE (molecular beam epitaxy) method, for example, RFMBE Growth (epitaxial growth) is performed by a process at a relatively low temperature (about 400 to 600 ° C. or less) such as a (radio-frequency molecular beam epitaxy) method or a PLD (Pulsed Laser Deposition) method.

(Step 3) Next, a surface flattening process of the ZnO single crystal substrate 11 is performed.
Planarization is performed by heat treatment and chemical mechanical polishing. A ZnO epitaxial layer may be formed. As a result of these treatments, the ZnO single crystal substrate 11 can obtain a flat surface at the atomic level. For example, the RMS value of AFM is about 0.2 nm or less. When the off-angle was applied, there was no step bunching and a uniform step could be observed.

(Step 4) Next, the first nitride semiconductor growth step is started. Thermal cleaning is performed in the growth chamber under atmospheric pressure or reduced pressure.
Specifically, it is heated in a vacuum at a temperature of 700 to 750 ° C. for 30 to 60 minutes to remove organic substances and the like.

  Here, a protective film 12 made of a nitride semiconductor (InGaN, AlInN, AlGaInN, etc.) may be formed on the back surface 11a and both side surfaces 11b of the ZnO single crystal substrate 11, but here, the protective film 12 has already been formed. Suppose that it is formed.

(Step 5) Next, the nitride semiconductor layer is grown on the surface of the ZnO single crystal substrate 11.
The group V material is grown by the RFMBE method having an RF radical cell capable of supplying nitrogen radicals. For example, the interface layer 13 is formed by repeating a stack of 2 to 4 units by combining a stack of 1 ML of InN and 5 ML of GaN as one unit.

As conditions for this step 5, for example, the growth temperature Tg = 400 to 600 ° C., the plasma power P = 300 to 500 W, and the nitrogen gas (N ₂ ) flow rate 1.0 to 5.0 sccm (standard cc / mIn). As the group III material, in the InN layer, the Ga metal material is evaporated in the Knudsen cell and supplied to the substrate for the high-purity In and GaN layers.

Subsequently, an InGaN layer 14 lattice-matched with the ZnO single crystal substrate 11 is grown. In this step, for example, the growth temperature is set to Tg = 400 to 600 ° C. The plasma power P is set to 300 to 500 W and the nitrogen gas (N ₂ ) flow rate is set to 1.0 to 5.0 sccm. As group III materials, high-purity In and Ga metal materials are evaporated in a Knudsen cell and supplied to the substrate. The In composition is adjusted to approximately 20%. The InGaN layer 14 has a total thickness of about 0.1 to 0.3 μm and grows to a thickness of at least 0.01 μm. The substrate temperature may be increased continuously or stepwise in the middle. Since the rate at which In and Ga are incorporated varies depending on the growth temperature, the flux of In is increased when the growth temperature is increased. Further, the nitrogen radical is adjusted so that the RHEED pattern is constant so that the V / III ratio on the surface is about 1.
Annealing may be performed during the growth of the InGaN layer 14.

(Step 6) Thereafter, the GaN layer 15 is grown.
The growth of the GaN layer 15 is performed using ammonia. The substrate temperature is raised to about 800 ° C., and growth is performed by irradiating In and Ga with the supply of ammonia. In this method, the growth rate of the GaN layer 15 is at most about 1 μm / h, so that a thick film cannot be grown. Introduced into HVPE equipment at InGaN / ZnO stage and grows. The GaN layer 15 may be grown with an MBE device before being introduced into the HVPE device. The PLD method may be used in addition to the MBE method. In the PLD method, since the kinetic energy of the Group 3 raw material is large, growth can be performed under relatively large surface migration even when the substrate temperature is low.

  The conditions of HVPE are as follows. The growth temperature is 1000 ° C. to 1100 ° C. Hydrogen is used as a carrier, and the group 3 material is metal Ga.

  The GaN template substrate 10 shown in FIG. 1 is manufactured by the above (Step 1) to (Step 6). The thickness of the GaN layer 15 is about 10 μm, and this GaN template substrate 10 can be used for device fabrication. In this case, MBE or MOCVD can be used for the growth of the GaN layer 15.

  By removing the protective film 12 and the ZnO single crystal substrate 11 of the GaN template substrate 10 thus manufactured, the self-standing GaN substrate 20 as the GaN-based semiconductor substrate shown in FIG. 2 can be manufactured.

  In this case, the GaN layer 15 has a thickness of 100 μm or more. After the protective film 12 on the back surface 11a is removed by dry etching, the ZnO single crystal substrate 11 is wet etched with carboxylic acid such as hydrochloric acid, phosphoric acid, or tartaric acid. Further, the contact resistance of the back surface can be lowered by removing the back surface side of the free-standing GaN substrate 20 by about several μm by chemical mechanical polishing. This step is often performed in an element process.

(Semiconductor light emitting device)
Next, the self-standing GaN substrate 20 shown in FIG. 2 is used as an epitaxial growth substrate (epitaxial wafer), and the element structure of the semiconductor light emitting element is laminated on the epitaxial wafer by high temperature MOCVD. Note that the self-standing GaN substrate 20 used here is the one that is removed up to the portion indicated by the broken line in FIG.

  Here, a case where an element structure of a semiconductor laser element is formed on the GaN layer 15 of the self-standing GaN substrate 20 will be described as an example. The self-standing GaN substrate 20 is not limited to a semiconductor light emitting element such as a semiconductor laser element LED, but can also be used as an epitaxial wafer for forming an element structure of a semiconductor element such as a power Schottky diode or FET.

  FIG. 3 is a cross-sectional view showing the element structure of the semiconductor laser element. This element structure is formed on this epitaxial wafer using the GaN layer 15 of the self-standing GaN substrate 20 as an epitaxial wafer. The GaN layer 15 has n-type conductivity doped with Si. The element structure formed on the GaN layer 15 includes an n-type GaN layer 31 serving as a buffer layer, an n-type GaN clad layer 32, and an InGaN formed on the GaN clad layer 32. An active layer 33, an AlGaN cladding layer 34 having p-type conductivity formed on the active layer 33, and a GaN contact layer 35 having p-type conductivity formed on the AlGaN cladding layer 34 are provided. Instead of the InGaN active layer 33, an active layer having a quantum well (QW) structure made of InGaN / GaN may be used.

  After stacking such a semiconductor device structure on the GaN layer 15 of the free-standing GaN substrate 20, the device process starts. As shown in FIG. 4, the ridge stripe 36 is processed by dry etching, and its side wall is protected by a protective film 37, and then a P-type electrode 38 is disposed. Further, an n-type lower electrode 39 is formed on the back surface side of the GaN layer 15 of the self-standing GaN substrate 20 that is an epitaxial wafer. Polishing is preferably performed before this. Next, as shown in FIG. 5, end mirrors 41 and 42 are formed by cleavage. An AR film and an HR film are formed on the end mirrors 41 and 42, respectively. A single element is divided along the ridge stripe 36 by dicing and die-bonded to a heat sink. A thick electrode pad may be prepared for the surface electrode by a method such as gold plating. A means for supplying current to the P-type electrode 38 is provided, for example, by wire bonding to the surface electrode.

Thereby, the fabrication of the semiconductor laser element 40 is completed.
According to 1st Embodiment described above, there exist the following effects.

  A thick GaN layer is grown on an InGaN / ZnO composite substrate having a lattice-matched InGaN layer 14 formed on the ZnO single crystal substrate 11 at a temperature of 1000 ° C. or higher with ammonia preferable for the growth of the GaN layer 15. Thus, the GaN template substrate 10 and the self-standing GaN substrate 20 having excellent orientation and a significantly reduced dislocation density can be produced.

  In addition, since the back surface 11a and both side surfaces 11b of the ZnO single crystal substrate 11 are protected in advance by the protective film 12, the ZnO single crystal substrate 11 is not destroyed by ammonia during the growth of the GaN layer 15, Therefore, the GaN layer 15 is not contaminated by Zn or oxygen. Therefore, it is possible to obtain the GaN template substrate 10 and the free-standing GaN substrate 20 having the GaN layer 15 having a good crystal quality with reduced threading dislocations as compared with the prior art.

  Since the ZnO single crystal substrate 11 capable of forming a large single crystal is used as the base substrate, the large GaN template substrate 10 and the freestanding GaN substrate 20 can be manufactured.

  Since the GaN layer 15 is grown on the basis of an InGaN / ZnO composite substrate having an InGaN layer 14 originally grown in lattice matching with a ZnO single crystal substrate 11 having a low dislocation density, the threading dislocation density of the GaN layer 15 is It is greatly reduced. For example, the threading dislocation density is 1E + 2 cm−2 or less.

  Furthermore, by removing a part of the GaN layer 15 to the position shown by the broken line in FIG. 2 to make the self-standing GaN substrate 20, the growth of the element structure can be performed with low strain by introducing thermal stress. A vertical electrode arrangement is possible.

  Even if the semiconductor laser device 40 having the active layer 33 in a large region is manufactured, an element in which no threading dislocation exists in the active layer 33 can be obtained, so that the device has a watt-class light output and has a practical lifetime. Can be obtained.

  The GaN template substrate 10 and the freestanding GaN substrate 20 can be used as an epitaxial growth substrate (epitaxial wafer) for a blue-violet semiconductor laser device having an oscillation wavelength near 405 nm.

  Further, by removing the GaN template substrate 10 shown in FIG. 1 up to the portion shown by the broken line in FIG. 2, a portion in which impurities such as Zn and O are mixed in the GaN layer 15 by producing the self-standing GaN substrate 20. Therefore, a self-standing GaN substrate having a GaN layer 15 of better crystal quality with reduced threading dislocations can be obtained.

(Second Embodiment)
FIG. 6 shows an InGaN template substrate 10A according to the second embodiment of the present invention.
An InGaN template substrate 10A as a GaN-based semiconductor substrate uses an InGaN layer 15A in which In is added to the GaN layer 15 instead of the GaN layer 15 of the GaN template substrate 10 according to the first embodiment shown in FIG. Yes. Other configurations of the InGaN template substrate 10A are the same as those of the GaN template substrate 10 shown in FIG. By removing the protective film 12 and the ZnO single crystal substrate 11 from the InGaN template substrate 10A, a self-standing InGaN substrate 20A as a GaN-based semiconductor substrate shown in FIG. 7 can be produced.

  In this case, the InGaN layer 15 has a thickness of 100 μm or more. After the protective film 12 on the back surface 11a is removed by dry etching, the ZnO single crystal substrate 11 is wet etched with carboxylic acid such as hydrochloric acid, phosphoric acid, or tartaric acid. Furthermore, the contact resistance of the back surface can be lowered by removing the back surface side of the freestanding InGaN substrate 20A by about several μm by chemical mechanical polishing. This step is often performed in an element process.

(Semiconductor light emitting device)
Next, the self-standing InGaN substrate 20A shown in FIG. 7 is used as an epitaxial growth substrate (epitaxial wafer), and the element structure of the semiconductor light emitting element is laminated on the epitaxial wafer by high temperature MOCVD. Note that the self-standing InGaN substrate 20A used here is one that has been removed up to the portion indicated by the broken line in FIG.

  Here, a case where the element structure of the semiconductor laser element is formed on the InGaN layer 15A of the freestanding InGaN substrate 20A will be described as an example. This self-standing InGaN substrate 20A is not limited to a semiconductor light emitting element such as a semiconductor laser element LED, but may be used as an epitaxial wafer for forming an element structure of a semiconductor element such as a Schottky diode for power or an FET.

  FIG. 8 is a cross-sectional view showing the element structure of the semiconductor laser element. This element structure is formed on this substrate using the InGaN layer 15A of the freestanding InGaN substrate 20A as an epitaxial wafer (substrate). The InGaN layer 15A has n-type conductivity doped with Si. The element structure formed on the InGaN layer 15A includes an InGaN layer 51 having n-type conductivity which is a buffer layer, an AlInGaN cladding layer 52 having n-type conductivity, and an InGaN formed on the AlInGaN cladding layer 52. The active layer 53 includes an AlInGaN clad layer 54 having p-type conductivity formed on the active layer 53, and an InGaN contact layer 55 having p-type conductivity formed on the AlInGaN clad layer 54. Instead of the InGaN active layer 53, an active layer having a multiple quantum well (MQW) structure made of GaN may be used.

After stacking such an element structure on the InGaN layer 15A of the freestanding InGaN substrate 20A that is an epitaxial wafer, the above-described element process is started. Then, a semiconductor laser element is manufactured as in the first embodiment.
According to 2nd Embodiment described above, in addition to the effect which the said 1st Embodiment show | plays, there exist the following effects.

  By using the InGaN layer 15A as a thick film and using the InGaN template substrate 10A or the self-standing InGaN substrate 20A, the distortion of the active layer 53 is reduced, and the oscillation wavelength of the semiconductor light emitting device can be increased. That is, it is possible to realize a semiconductor light emitting element that emits light in a visible light region from blue to red, particularly visible light having a longer wavelength than blue (for example, green).

  Since the lattice constant of the ZnO single crystal substrate 11 is close to that of InGaN (lattice matching), phase separation is suppressed even if the In composition of the active layer 53 is increased. As a result, an InGaN active layer 53 having a uniform In composition can be obtained even if the In composition is increased, so that light is emitted in the visible light region from blue to red, particularly visible light having a longer wavelength than blue (for example, green). A semiconductor light emitting device can be realized. In addition, this invention can also be changed and embodied as follows.

  In the element structure of the semiconductor laser device shown in FIG. 3, instead of the GaN layer 15, GaN layer 31 and GaN cladding layer 32 having n-type conductivity, Mg is doped to have p-type conductivity, respectively. Alternatively, the GaN layer 15, the GaN layer 31, and the GaN cladding layer 32 may be used. In this case, instead of the AlGaN cladding layer 34 and the GaN contact layer 35 each having p-type conductivity, an AlGaN cladding layer 34 and a GaN contact layer 35 each having n-type conductivity doped with Si are used.

  In the element structure of the semiconductor laser device shown in FIG. 8, instead of the InGaN layer 15A, InGaN layer 51, and AlInGaN cladding layer 52 each having n-type conductivity, Mg is doped to have p-type conductivity. The InGaN layer 15A, the InGaN layer 51, and the AlInGaN clad layer 52 may be used. In this case, instead of the AlInGaN cladding layer 54 and the InGaN contact layer 55 each having p-type conductivity, the AlInGaN cladding layer 54 and the InGaN contact layer 55 each having n-type conductivity doped with Si are used.

  In each of the above embodiments, by setting the stripe width of the semiconductor laser element to 100 μm or more and the cavity length to 1000 mm or more, a semiconductor laser element having a practical life at a light output of 1 W or more in the transverse mode multi is obtained. It is done.

  In each of the above embodiments, even when the active layer 15 made of InGaN is made of AlGaInN, the lattice constant of the ZnO single crystal substrate 12 is close to AlGaInN (lattice matching) like InGaN, so that the active layer 15 Even if the composition of In is increased, phase separation is suppressed. As a result, an AlGaInN active layer having a uniform In composition can be obtained even if the In composition is increased, so that light is emitted in the visible light region from blue to red, particularly visible light having a longer wavelength than blue (eg, green). A semiconductor light emitting device can be realized.

Sectional drawing which shows the GaN template board | substrate which concerns on 1st Embodiment. Sectional drawing which shows a self-standing GaN substrate. Sectional drawing which shows the element structure formed on the self-supporting GaN substrate shown in FIG. Sectional drawing which shows the semiconductor laser element formed on the self-supporting GaN substrate shown in FIG. Explanatory drawing of cleavage and dicing. Sectional drawing which shows the InGaN template substrate which concerns on 2nd Embodiment. Sectional drawing which shows a self-supporting InGaN substrate. Sectional drawing which shows the element structure formed on the self-supporting InGaN substrate shown in FIG.

Explanation of symbols

10: GaN template substrate 10A: InGaN template substrate 11: ZnO single crystal substrate 11a: back surface 11b: side surface 11c: surface 12: protective film 13: interface layer 14: InGaN layer 15: GaN layer 15A: InGaN layer 20: freestanding GaN substrate 20A: Freestanding InGaN substrate 31: GaN layer 32: GaN cladding layer 33: InGaN active layer 34: AlGaN cladding layer 35: GaN contact layer 36: Ridge stripe 40: Semiconductor laser device as a semiconductor device 51: InGaN layer 52: AlInGaN cladding Layer 53: InGaN active layer 54: AlInGaN cladding layer 55: InGaN contact layer

Claims (13)

A ZnO substrate;
A protective film formed on one surface and side surface of the ZnO substrate;
An interface layer formed on the other surface of the ZnO substrate;
An InGaN layer lattice-matched to the ZnO substrate formed on the interface layer;
A GaN layer of at least 2 μm or more formed on the InGaN layer;
A GaN-based semiconductor substrate, comprising: a GaN template substrate comprising:   The GaN-based semiconductor substrate according to claim 1, wherein the interface layer includes a GaN layer having a critical thickness or less, an InN layer, and a composite layer obtained by combining these layers. A first step of forming a protective film on one surface and side surface of the ZnO substrate;
A second step of forming an interface layer on the other surface of the ZnO substrate;
A third step of forming an InGaN layer lattice-matched to the ZnO substrate on the interface layer;
And a fourth step of forming a GaN layer having a thickness of at least 2 μm on the InGaN layer to produce a GaN template substrate.   4. The method of manufacturing a GaN-based semiconductor substrate according to claim 3, further comprising a fifth step of manufacturing a self-standing GaN substrate by removing the protective film and the ZnO substrate.   The method further comprises a sixth step of fabricating a self-standing GaN substrate by removing the protective film, the ZnO substrate, the interface layer, the InGaN layer, and a part of the GaN layer that forms an interface with the InGaN layer. The method for producing a GaN-based semiconductor substrate according to claim 3.   A semiconductor device comprising a semiconductor device structure formed on the self-standing GaN substrate according to claim 4.   The semiconductor device structure includes an AlGaN cladding layer of a first conductivity type formed on the free-standing GaN substrate, an InGaN active layer formed on the AlGaN cladding layer, or an active layer of a quantum well structure made of GaN, A second light emitting type AlGaN cladding layer formed on the active layer and a second conductivity type GaN contact layer formed on the AlGaN cladding layer, and configured as a semiconductor light emitting device. The semiconductor device according to claim 6. A ZnO substrate;
A protective film formed on one surface and side surface of the ZnO substrate;
An interface layer formed on the other surface of the ZnO substrate;
An InGaN layer lattice-matched to the ZnO substrate formed on the interface layer;
A GaN-based semiconductor substrate, comprising: an InGaN template substrate comprising an InGaN layer of at least 2 μm formed on the InGaN layer. A first step of forming a protective film on one surface and side surface of the ZnO substrate;
A second step of growing an interface layer on the other surface of the ZnO substrate;
A third step of forming an InGaN layer lattice-matched to the ZnO substrate on the interface layer;
And a fourth step of forming an InGaN layer of at least 2 μm or more on the InGaN layer to produce an InGaN template substrate.   10. The method of manufacturing a GaN-based semiconductor substrate according to claim 9, further comprising a fifth step of fabricating a self-supporting InGaN substrate by removing the protective film and the ZnO substrate.   The method further includes a sixth step of fabricating a self-supporting InGaN substrate by removing the protective film of the InGaN template substrate, the ZnO substrate, the interface layer, and a part of the InGaN layer that forms an interface with the interface layer. The method for producing a GaN-based semiconductor substrate according to claim 9.   A semiconductor device comprising a semiconductor device structure formed on the self-standing InGaN substrate according to claim 10.   The semiconductor device structure includes an AlInGaN cladding layer of a first conductivity type formed on the freestanding InGaN substrate, an InGaN active layer formed on the AlInGaN cladding layer, or an active layer of a multiple quantum well structure made of GaN, A second light emitting type AlInGaN clad layer formed on the active layer and a second light conductive type InGaN contact layer formed on the AlInGaN clad layer, and configured as a semiconductor light emitting device The semiconductor device according to claim 12.

Images