JP3988245B2 - Nitride III-V compound semiconductor growth method and semiconductor device manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a method for growing a nitride-based III-V compound semiconductor.And method for manufacturing semiconductor deviceIn particular, the present invention is suitable for application to a semiconductor laser, a light emitting diode, or an electron transit device using a nitride III-V compound semiconductor.
[0002]
[Prior art]
Since GaN-based semiconductors are direct transition semiconductors, and their forbidden band ranges from 1.9 eV to 6.2 eV, it is possible to realize a light-emitting element capable of emitting light from the visible region to the ultraviolet region. It has attracted attention and its development is actively underway. In addition, this GaN-based semiconductor has great potential as a material for an electron transit device. That is, the saturation electron velocity of GaN is about 2.5 × 10⁷cm / s is larger than Si, GaAs and SiC, and the breakdown electric field is about 5 × 10⁶V / cm and second largest after diamond. For these reasons, GaN-based semiconductors have been expected to have great potential as materials for high-frequency, high-temperature, high-power electron transit devices.
[0003]
By the way, generally, in order to obtain a high-performance semiconductor device, the crystal quality of the semiconductor layer constituting the semiconductor device is very important. For example, in a conventional optical element using a GaAs-based semiconductor, the stacking fault density of the semiconductor layer is 10^Threecm^-2It is as follows. In contrast, GaN-based semiconductors are usually grown on substrates having different lattice constants, such as sapphire and SiC, but the stacking fault density is 10⁸-10^Tencm^-2The degree and extremely high. Despite the existence of such high-density crystal defects due to the nature of GaN-based semiconductors, light-emitting diodes have already been put to practical use, semiconductor lasers have also achieved room-temperature continuous oscillation, and electron transit devices have also been prototyped. It has been reported in recent years.
[0004]
However, it has been experimentally confirmed that GaN-based semiconductors with few crystal defects tend to have high luminous efficiency, and theoretical calculations indicate that electron mobility is defined by crystal defects when there are few carriers. It has been pointed out. For this reason, in recent years, methods for reducing crystal defects in GaN-based semiconductors have been sought. In particular, reduction of crystal defects in a GaN-based semiconductor is essential for extending the lifetime of a GaN-based semiconductor laser.
[0005]
A conventional measure for reducing crystal defects in a GaN-based semiconductor will be described by taking GaN as an example. The first strategy for reducing the crystal defects of GaN is to select a growth substrate that is as close as possible to the lattice constant and crystal structure of GaN. For example, a c-plane sapphire substrate that is most often used as a growth substrate has a lattice constant difference of 13% from that of GaN. When this is grown on the c-plane sapphire substrate, the c-plane sapphire substrate has a high GaN layer. This is a cause of density crystal defects. Also, the SiC substrate has a lattice constant difference of about 3.5% with GaN, and the GaN layer grown on this SiC substrate has a smaller crystal defect density than the GaN layer grown on the c-plane sapphire substrate. It is said. The second strategy for reducing crystal defects in GaN is to use a selective growth technique (J. Crystal Growth, 144 (1994) 133). In this method, a single-crystal GaN layer is formed in advance on a c-plane sapphire substrate or SiC substrate, and SiO 2 is formed thereon.₂A second growth of GaN is performed with a growth mask made of a film or SiN film formed. In this case, when the GaN crystal grown on the GaN layer in the opening that is not covered with the growth mask extends in the lateral direction (on the growth mask), penetration defects inherited from the base are blocked by the growth mask. Therefore, the GaN layer grown on the growth mask becomes a high-quality crystal with a lower crystal defect density. This technology has been used in the technology of growing single-crystal GaAs on a Si substrate (GaAs-on-Si substrate technology), but has recently been tried in GaN crystal growth and succeeded in reducing crystal defects. (Jpn.J.Appl.Phys., 36 (1997) L899).
[0006]
The above-described selective growth technique of GaN will be described in more detail. That is, in this technique, as shown in FIG. 16, first, an amorphous GaN buffer layer having a thickness of, for example, 20 to 30 nm is grown on a c-plane sapphire substrate 101 at a low temperature of, for example, about 500 to 600 ° C. Thereafter, the substrate temperature is raised to about 1000 ° C., and the GaN buffer layer is crystallized by solid phase epitaxial growth to form a polycrystalline GaN layer with aligned crystal grains. Then, when GaN is grown on this polycrystalline GaN layer to a certain extent (typically about 3 μm), the stacking fault density becomes 10^Tencm^-2A single-crystal GaN layer 102 of the order is obtained. Next, SiO is deposited on the GaN layer 102.₂A stripe-shaped growth mask 103 made of a film or the like is formed, and GaN is grown at a temperature of about 1000 ° C. by metal organic chemical vapor deposition (MOCVD) or hydride vapor phase epitaxy (HVPE). Then, the GaN grown on the GaN layer 102 in the opening not covered with the growth mask spreads on the growth mask 103 by lateral growth, and the GaN has a certain thickness, for example, 2 to 5 times the mask width. When grown to a thickness (for example, 8 to 20 μm), the GaN crystals grown in the lateral direction from the openings of the growth mask 103 are combined to grow a continuous single-crystal GaN layer 104. At this time, not only the GaN layer 104 on the growth mask 103 but also the threading dislocations of the GaN layer 104 on the opening of the growth mask 103 are bent in the lateral direction, and crystal defects as a whole of the GaN layer 104 are reduced.
[0007]
[Problems to be solved by the invention]
However, although the conventional selective growth technique described above is effective in reducing crystal defects of GaN, it has the following drawbacks. That is, first, in order to grow the single crystal GaN layer 104 having a low crystal defect density, it is necessary to form the single crystal GaN layer 102 on the c-plane sapphire substrate 101 in advance. This means that the crystal growth must be performed twice, and the cost of crystal growth is almost doubled. Secondly, the selective growth of the GaN layer 104 needs to be continued until the side surfaces of the GaN layer 104 grown from the openings of the growth mask 103 merge together to reduce defects. The GaN layer 102 must be grown as thick as at least about 8 μm. This means that much growth time and raw materials are consumed, and the cost of crystal growth becomes high.
[0008]
  Accordingly, an object of the present invention is to provide a method for growing a nitride III-V compound semiconductor capable of growing a high-quality single crystal nitride III-V compound semiconductor having a low crystal defect density at a low cost.And manufacturing method of semiconductor device using this growth methodIs to provide.
[0009]
[Means for Solving the Problems]
The present inventor has intensively studied to solve the above-described problems of the prior art. The outline will be described below.
[0010]
Consider a case where GaN crystal growth is performed on a sapphire substrate by a MOCVD method at a growth temperature of about 1000 ° C. without growing a GaN buffer layer by low-temperature growth. In this case, the grown GaN layer is not flat on the surface, and has a shape in which large GaN clusters overlap. This is due to the interaction between the surface of the sapphire substrate at the initial stage of crystal growth and Ga and N involved in crystal growth. That is, the residence time of Ga and N on the surface of the sapphire substrate is short, and as a result, the surface concentration of Ga and N is small, so that the generation of crystal nuclei is small. In other words, the degree of supersaturation for generating crystal nuclei is small. In this way, since the number of crystal nuclei initially generated on the surface of the sapphire substrate is small and sparsely scattered, the raw material supplied at the time of growth concentrates on this few crystal nuclei, and thus each single crystal nucleus. Looking at the crystal nuclei, the degree of supersaturation for GaN crystal growth increases. As a result, the growth rate of each crystal nuclei is overwhelmingly high, each grows at an independent growth rate, and GaN folds three-dimensionally. The surface morphology.
[0011]
Therefore, in order to obtain a GaN layer with a flat surface, the density of crystal nuclei on the surface of the sapphire substrate is overwhelmingly increased, and each crystal nucleus grows slowly. It is necessary to smoothly unite with the nucleus. This is realized by a low-temperature growth GaN buffer layer. In the low temperature growth, the residence time of Ga and N on the surface of the sapphire substrate is very long, so that everything that reaches the surface is precipitated. However, since the surface movement speeds of Ga and N are very small, the grown GaN does not become a crystal but is amorphous. Thereafter, when the growth is performed by raising the growth temperature to about 1000 ° C., the underlying surface can be regarded as a collection of crystal nuclei, and therefore, when the source gas is supplied, the growth starts from each crystal nuclei. Then, each crystal nucleus performs two-dimensional growth at substantially the same speed, and crystal interfaces merge with each other and grow together while generating defects. At this time, the generated crystal defects are merged with nearby crystal defects to reduce the number thereof.⁹cm^-2The crystal defect density becomes about a degree.
[0012]
The above is a method for growing a single crystal GaN layer using a GaN buffer layer by low-temperature growth. Here, a stripe-shaped growth mask is directly formed on an arbitrary substrate different from GaN to be grown, for example, a sapphire substrate. Consider the case of growing GaN on a sapphire substrate, and consider the growth at this time. First, the growth mask was attached to any location on the surface of the growth mask so that the shortest distance from any point on the surface to the edge thereof was smaller than the diffusion length of Ga and N on the surface. The mask width is determined so that Ga and N also reach the substrate surface at the opening of the growth mask by surface diffusion. The growth mask is directly formed on the substrate and GaN is grown. At this time, the amount of raw material supplied to the substrate surface at the opening of the growth mask is increased to increase the degree of supersaturation, thereby generating nuclei. Crystal nuclei are generated at high density by increasing the speed. At this time, these crystal nuclei are epitaxially grown on the substrate surface in the opening of the growth mask according to the crystal orientation of the substrate, and these crystal nuclei grow gradually. Here, since the growth is relatively free on the substrate surface near the center of the opening of the growth mask, the surface of the growing GaN layer is not necessarily flat. In contrast, a series of crystal nuclei generated in alignment with the mask edge merge together when grown to the same thickness as the mask, but if the thickness exceeds the mask thickness, the mask edge cannot grow freely. A linear crystal growth front parallel to the stripe direction is formed. That is, at the edge of the mask, a crystal growth front is formed along the stripe direction of the growth mask, which proceeds on the growth mask and grows laterally, and increases its thickness. The GaN crystal grown on the growth mask spreads to the center of the opening of the growth mask as the thickness increases, and eventually the entire surface grows flat, with a flat surface and a low crystal defect density. A crystalline GaN layer is obtained.
[0013]
As described above, a growth mask is directly formed on an arbitrary substrate different from GaN. At this time, the shortest distance from any point on the surface to the end of the growth mask is the diffusion length of Ga and N on the surface. By growing GaN in this state, crystal nuclei with uniform orientation are formed at a high density on the substrate surface at the opening of the growth mask, and the group of these crystal nuclei is laterally distributed. By controlling the growth in the direction (graphoepitaxy), an amorphous layer such as a GaN buffer layer by low-temperature growth is not grown on the substrate in advance, and the surface is flat and has a low crystal defect density. A single crystal GaN layer can be grown.
[0014]
The present invention has been devised based on the above studies by the present inventors.
[0015]
  That is, in order to achieve the above object, the first invention of the present invention is:
  In the method of growing a nitride III-V compound semiconductor, a nitride III-V compound semiconductor is grown on a substrate made of a material different from the nitride III-V compound semiconductor.
  With the growth mask directly formed on the substrate, a nitride III-V compound semiconductor is formed on the substrate in each opening of the growth mask.700Selectively grow at a growth temperature of ~ 800 ° CAlmost filled each openingrear,At a growth temperature of 950-1050 ° C.A nitride-based III-V group compound semiconductor is laterally grown from each opening to combine the nitride-based III-V group compound semiconductor to form a continuous film.
  It is characterized by this.
  The second invention of this invention is:
  In a method for manufacturing a semiconductor device in which a nitride III-V compound semiconductor is grown on a substrate made of a material different from that of a nitride III-V compound semiconductor,
  With the growth mask directly formed on the substrate, a nitride III-V compound semiconductor is selectively grown on the substrate at each opening in the growth mask at a growth temperature of 700 to 800 ° C. to almost fill each opening. After that, the nitride III-V compound semiconductor is laterally grown from each opening at a growth temperature of 950 to 1050 ° C., thereby combining the nitride III-V compound semiconductor to form a continuous film. Made
  It is characterized by this.
[0017]
In the present invention, the growth mask is formed so that the nitride III-V compound semiconductor can be selectively grown on the substrate at the opening of the growth mask, and the growth temperature is selected. Growth masks typically balance the growth temperature used and the shortest distance from any point on the growth mask surface to the edge of the growth mask is the nitride III-V group at the growth mask surface. It is formed so as to be smaller than the diffusion length of atoms or molecules involved in the growth of the compound semiconductor. The shape of the growth mask can be various shapes, and can be determined as needed. Typically, the growth mask is selected to have a stripe shape extending in one direction with respect to the substrate. The growth temperature is in balance with the growth mask to be used, and the shortest distance from any point on the growth mask surface to the edge of the growth mask is that of the nitride III-V compound semiconductor on the growth mask surface. The temperature is selected to be smaller than the diffusion length of atoms or molecules involved in the growth. Generally, the higher the growth temperature, the higher the growth selectivity. From the viewpoint of sufficiently ensuring this selectivity, the growth temperature is generally selected to be at least 610 ° C. or higher, preferably 650 ° C. or higher, more preferably 700 ° C. or higher, and even more preferably 750 ° C. or higher.
[0018]
In this invention, as a material for the growth mask, when a nitride III-V compound semiconductor is grown, the nitride III-V compound semiconductor does not grow or at least hardly grows thereon. Typically, a dielectric or insulator, specifically silicon oxide (SiO 2)₂) Or silicon nitride (SiN) is used. As the substrate, a sapphire substrate, a SiC substrate, a Si substrate, a spinel substrate, or the like is used.
[0019]
In the present invention, typically, a nitride III-V compound semiconductor is selectively grown on the substrate in the opening of the growth mask to substantially fill the opening, and then the growth temperature is raised to increase the nitride III. -Group V compound semiconductor is grown until a continuous film is formed. Specifically, for example, the growth temperature when the nitride III-V compound semiconductor is selectively grown on the substrate in the opening of the growth mask to fill the opening is 610 to 800 ° C., and the subsequent growth temperature is 950-1050 ° C.
[0020]
In this invention, the nitride-based III-V group compound semiconductor contains at least one group III element selected from the group consisting of Ga, Al, In and B, and at least N, and optionally further contains As or P. It consists of the V group element to contain. Specific examples of the nitride III-V group compound semiconductor include GaN, AlGaN, AlN, GaInN, AlGaInN, InN, and the like.
[0021]
In the present invention configured as described above, the nitride-based III-V compound semiconductor is grown on the substrate in a state where the growth mask is directly formed on the substrate. A growth mask is formed on the substrate so that a nitride III-V compound semiconductor can be selectively grown, and by selecting a growth temperature, at the time of growth, first, on the substrate at the opening of the growth mask. The openings of the growth mask were filled by the growth of crystal nuclei generated at a high density with a constant crystal orientation by epitaxial growth, and then the growth progressed on the growth mask by lateral growth, and lateral growth was made from each opening. Crystals merge to form a continuous film. A nitride-based III-V compound semiconductor grown in this manner has a low crystal defect density and high quality single crystal by reducing crystal defects such as threading dislocations inherited from the base during the lateral growth. It becomes a crystal. Further, in this case, it is only necessary to form a growth mask directly on the substrate and to grow a nitride III-V group compound semiconductor on the growth mask.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings of the embodiments, the same or corresponding parts are denoted by the same reference numerals.
[0023]
1 to 8 show a method for growing a GaN layer according to the first embodiment of the present invention.
[0024]
In the first embodiment, first, as shown in FIG. 1 and FIG. 2, SiO is formed on the c-plane sapphire substrate 1 by, for example, the CVD method.₂After the film 2 is formed, this SiO 2₂The film 2 is patterned into a stripe shape extending in the <11-20> direction of the c-plane sapphire substrate 1 by lithography and etching to form a growth mask. Here, SiO as the growth mask₂Width W of membrane 2₁This SiO is the growth temperature used.₂The shortest distance from an arbitrary point on the surface of the film 2 to its end is selected to be smaller than the diffusion lengths of Ga and N on the surface. Specifically, this SiO₂Width W of membrane 2₁Is 3 μm, for example, and this SiO₂Width W of opening of membrane 2₂Is, for example, 1.5 μm. This SiO₂The thickness of the film 2 is 0.1 μm, for example. FIG. 9 shows SiO as a growth mask.₂The scanning electron microscope (SEM) photograph of the surface of the c-plane sapphire substrate 1 on which the film 2 is formed is shown.
[0025]
Next, SiO as a growth mask₂The c-plane sapphire substrate 1 on which the film 2 is formed is introduced into the reaction tube of the MOCVD apparatus. In the reaction tube, first, hydrogen (H₂) And nitrogen (N₂) At a flow rate of 8 l / min and 7 l / min, respectively, followed by thermal treatment at 1050 ° C. for 10 minutes to thermally clean the surface of the c-plane sapphire substrate 1. In a stable state, ammonia (NH_Three) And trimethylgallium (TMG) are simultaneously supplied at a flow rate of 10 l / min and 100 μmol / min, respectively, to grow GaN. Here, the growth temperature is 750 ° C.
[0026]
In the initial stage of growth, as shown in FIG.₂On the surface of the c-plane sapphire substrate 1 in the opening of the film 2, GaN crystal nuclei 3 are epitaxially grown at a high density with a fixed crystal orientation relative to the crystal orientation of the c-plane sapphire substrate 1. At this time, SiO₂The diffusion length of Ga and N on the surface of the film 2 is the SiO 2₂This SiO 2 is longer than the shortest distance from any point on the surface of the film 2 to its edge,₂Crystal nuclei 3 are hardly generated on the surface of the film 2. That is, the crystal nucleus 3 is made of SiO.₂It is selectively generated on the surface of the c-plane sapphire substrate 1 in the opening of the film 2.
[0027]
Each crystal nucleus 3 grows with the passage of time, and coalesces with each other after a certain period of time. As shown in FIG.₂A substantially single crystal GaN layer 4 is grown on the c-plane sapphire substrate 1 in the opening of the film 2. At this time, the surface of the GaN layer 4 is usually a surface with irregularities.
[0028]
As time passes, the surface of the GaN layer 4 becomes SiO 2 as shown in FIG.₂It becomes almost the same height as the surface of the film 2.
[0029]
At this time, the growth temperature is raised to, for example, about 1000 ° C., and the flow rate of TMG is set to, for example, 30 μmol / min to continue the growth of GaN. Thereby, as shown in FIG. 6, the GaN layer 4 increases the thickness while increasing the thickness of the SiO 2 layer.₂By lateral growth of the film 2 in the width direction, SiO 2₂It also grows on the film 2. Usually, even at this point, the surface of the GaN layer 4 is uneven. When the GaN layer 4 is grown to a thickness of about 2 μm, the surface of the GaN layer 4 has almost no irregularities as shown in FIG. The plane orientation of the side surface of the GaN layer 4 grown in this way is {1-101}.
[0030]
As the growth of the GaN layer 4 further progresses, SiO₂As shown in FIG. 8, when the GaN layers 4 laterally grown from the openings of the film 2 are merged at their side surfaces and the thickness of the GaN layer 4 is about 6 μm, a single surface with a flat surface is obtained. A crystalline GaN layer 4 is obtained as a continuous film.
[0031]
FIG. 10 shows that the GaN layer is grown for a time (about 30 seconds) necessary for growing the GaN layer to a thickness of 0.1 μm when the growth rate in the conventional GaN layer growth method for growing the GaN buffer layer is used. 2 shows an SEM photograph of the surface of the GaN layer 4. From FIG. 10, SiO₂This SiO 2 from the edge of the opening of the film 2₂A lateral growth of the GaN layer 4 on the film 2 can be seen. In this case, the width of the GaN layer 4 is 2.1 μm, while SiO 2₂Width W of opening of membrane 2₂Is 1.5 μm, the GaN layer 4 is made of SiO.₂SiO on both sides of the opening of film 2₂Each film grows laterally by 0.3 μm. As a result of X-ray diffraction, it was confirmed that the GaN layer 4 was not amorphous but a c-axis oriented crystal.
[0032]
  In addition, SiO of the GaN layer 4₂SiO until lateral growth on film 2 begins₂Since no growth of the GaN layer 4 is observed on the film 2 and complete selectivity is obtained, SiO 2 is obtained.₂The diffusion length of Ga and N on the surface of the film 2 is considered to be at least 3 μm or more at a growth temperature of 750 ° C. In fact, according to a separate experiment,3μm square SiO₂Since no precipitation was observed on the surface of the film, the diffusion length of Ga and N at the growth temperature of 750 ° C. is3μm or more.
[0033]
For comparison, when the growth temperature was set to 500 ° C. and the GaN layer 4 was grown to a thickness of 0.1 μm, SiO 2₂The GaN layer 4 grew on the entire surface including the surface of the film 2, and selectivity was not obtained. FIG. 11 shows an SEM photograph of the GaN layer 4 at that time. Further, when the growth temperature is 600 ° C. and the GaN layer 4 is grown to a thickness of 0.1 μm, the particle size of the grown particles is larger than that when the growth temperature is 500 ° C.₂The GaN layer 4 grew on the entire surface including the surface of the film 2, and selectivity was not obtained. From this, the diffusion length of Ga and N at a growth temperature of 600 ° C. is considered to be 3 μm or less. FIG. 12 shows an SEM photograph of the GaN layer 4 at that time.
[0034]
As described above, according to the first embodiment, stripe-shaped SiO 2 as a growth mask on the c-plane sapphire substrate 1 is used.₂The film 2 is directly formed, and this SiO 2₂The width of the film 2 is made narrower than the diffusion length of Ga and N at the growth temperature.₂By growing GaN on the c-plane sapphire substrate 1 on which the film 2 is formed, a single crystal growth of a high quality single crystal GaN layer 4 having a flat surface and a low crystal defect density can be achieved at low cost. Can be grown in.
[0035]
Next explained is a GaN layer growth method according to the second embodiment of the invention.
[0036]
In the second embodiment, when the GaN layer 4 is grown to the state shown in FIG. 5, the growth temperature is 850 ° C., and H₂Flow rate of 0, N₂And the TMG supply amount is 150 μmol / min. Thereafter, the growth temperature is raised to about 1000 ° C., the TMG flow rate is reduced to 15 μmol / min, and the GaN layer 4 is grown. Here, when the GaN layer 4 is grown to the state shown in FIG.₂The flow rate of 0 is set to 0 because the growth temperature is relatively high at 850 ° C., so that the effective supply amount of raw material gas that contributes to growth is increased and the degree of supersaturation for generating crystal nuclei 3 is increased. is there. On the other hand, the reason why the flow rate of TMG is reduced to 15 μmol / min after the GaN layer 4 is grown to the state shown in FIG. 5 is to return to a low crystal growth rate. Others are the same as those in the first embodiment, and a description thereof will be omitted.
[0037]
According to the second embodiment, the same advantages as those of the first embodiment can be obtained.
[0038]
Next explained is a GaN semiconductor laser manufacturing method according to the third embodiment of the invention. This manufacturing method is shown in FIGS. This GaN semiconductor laser has an SCH (Separate Confinement Heterostructure) structure.
[0039]
In the third embodiment, as shown in FIG. 13, first, a stripe-shaped SiO 2 as a growth mask is formed on the c-plane sapphire substrate 1 by the same method as in the first or second embodiment.₂A film 2 is directly formed, and a monocrystalline GaN layer 4 having a flat surface and a low crystal defect density is grown as a continuous film on the GaN layer 4 by MOCVD. GaN contact layer 5, n-type AlGaN cladding layer 6, n-type GaN optical waveguide layer 7, for example Ga_1-xIn_xN / Ga_1-yIn_yAn active layer 8 having an N multiple quantum well structure, a p-type GaN optical waveguide layer 9, a p-type AlGaN cladding layer 10 and a p-type GaN contact layer 11 are sequentially grown. At this time, since the GaN layer 4 which is the base of these layers is a high-quality single crystal having a low crystal defect density, these layers are also a high-quality single crystal having a low crystal defect density. Here, the n-type GaN contact layer 5, the n-type AlGaN cladding layer 6, the n-type GaN optical waveguide layer 7, the p-type GaN optical waveguide layer 9, the p-type AlGaN cladding layer 10 and the p-type GaN, which are layers not containing In. The growth temperature of the contact layer 11 is about 1000 ° C., for example, and Ga is a layer containing In._1-xIn_xN / Ga_1-yIn_yThe growth temperature of the active layer 8 having the N multiple quantum well structure is set to 700 to 800 ° C., for example. As an example of the thicknesses of these layers, the n-type GaN contact layer 5 is 3 μm, the n-type AlGaN cladding layer 6 is 0.5 μm, the n-type GaN optical waveguide layer 7 is 0.1 μm, and the p-type GaN light The wave layer 9 is 0.1 μm, the p-type AlGaN cladding layer 10 is 0.5 μm, and the p-type GaN contact layer 11 is 0.5 μm. Further, the n-type GaN contact layer 5, the n-type AlGaN cladding layer 6 and the n-type GaN optical waveguide layer 7 are doped with, for example, Si as a donor, and the p-type GaN optical waveguide layer 9, the p-type AlGaN cladding layer 10 and the p-type are doped. The GaN contact layer 11 is doped with, for example, Mg as an acceptor. Thereafter, electrical activation of donors and acceptors doped in these layers, particularly electrical activity of acceptors doped in the p-type GaN optical waveguide layer 9, the p-type AlGaN cladding layer 10 and the p-type GaN contact layer 11. A heat treatment is performed for conversion. The temperature of this heat treatment is about 700 ° C., for example.
[0040]
Next, a stripe-shaped resist pattern (not shown) having a predetermined width is formed on the p-type GaN contact layer 11, and then the p-type AlGaN is formed by, for example, reactive ion etching (RIE) using the resist pattern as a mask. Etching is performed to a depth halfway in the thickness direction of the cladding layer 10 to form a ridge portion. Next, after removing this resist pattern, a stripe-shaped resist pattern (not shown) having a predetermined width is formed on the p-type GaN contact layer 11 and the p-type AlGaN cladding layer 10, and this resist pattern is used as a mask, for example. Etching to a depth in the thickness direction of the n-type GaN contact layer 5 by the RIE method results in a p-type GaN contact layer 11, a p-type AlGaN cladding layer 10, a p-type GaN optical waveguide layer 9, an active layer 8, n The upper layer portions of the n-type GaN optical waveguide layer 7, the n-type AlGaN cladding layer 6 and the n-type GaN contact layer 5 are patterned in a stripe shape. FIG. 14 shows a state after this patterning is completed.
[0041]
Next, as shown in FIG. 15, after removing the resist pattern used for the etching mask, a p-side electrode 12 made of, for example, a Ni / Au film or a Ni / Pt / Au film is formed on the p-type GaN contact layer 11. At the same time, an n-side electrode 13 made of, for example, a Ti / Al film is formed on the etched n-type GaN contact layer 5.
[0042]
Thereafter, the c-plane sapphire substrate 1 having the laser structure formed as described above is processed into a bar shape by cleavage or the like to form both resonator end faces, and further, end face coating is applied to these resonator end faces. Then, this bar is chipped by cleaving or the like. As described above, the target GaN semiconductor laser having the SCH structure is manufactured.
[0043]
According to the third embodiment, since the GaN layer 4 serving as a base of the semiconductor layer forming the laser structure can be grown at a low cost by one growth, the GaN-based semiconductor laser can be made lower than the conventional one. Can be manufactured at cost.
[0044]
As mentioned above, although embodiment of this invention was described concretely, this invention is not limited to the above-mentioned embodiment, The various deformation | transformation based on the technical idea of this invention is possible.
[0045]
For example, the numerical values, structures, substrates, raw materials, processes, and the like given in the first, second, and third embodiments are merely examples, and if necessary, numerical values, structures, substrates, raw materials that are different from these numerical values. A process or the like may be used.
[0046]
In the first, second, and third embodiments described above, stripe-shaped SiO2 as a growth mask is used.₂The extending direction of the film 2 is set to the <11-20> direction of the c-plane sapphire substrate 1, and this stripe-shaped SiO 2₂The extending direction of the film 2 may be set in the <1-100> direction.
[0047]
In the first, second, and third embodiments described above, the c-plane sapphire substrate is used as the substrate, but an SiC substrate, Si substrate, spinel substrate, or the like may be used as necessary. Similarly, as the growth method, in addition to the MOCVD method, an HVPE method or the like may be used.
[0048]
Furthermore, in the above-described third embodiment, the case where the present invention is applied to the manufacture of a GaN-based semiconductor laser has been described. However, the present invention is not limited to a GaN-based light emitting diode but also a GaN-based electron transit such as a GaN-based FET. You may apply to manufacture of an element.
[0049]
【The invention's effect】
As described above, according to the first aspect of the present invention, the nitride III-V group compound semiconductor is grown on the substrate with the growth mask directly formed on the substrate. A single crystal nitride III-V compound semiconductor having a low crystal defect density and high quality can be grown at low cost.
[0050]
According to the second aspect of the present invention, a semiconductor device using a nitride III-V compound semiconductor can be manufactured at low cost.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view for explaining a growth method of a GaN layer according to a first embodiment of the present invention.
FIG. 2 is a plan view corresponding to FIG. 1;
FIG. 3 is a cross-sectional view for explaining the growth method of the GaN layer according to the first embodiment of the present invention.
FIG. 4 is a cross-sectional view for explaining a GaN layer growth method according to the first embodiment of the present invention;
FIG. 5 is a cross-sectional view for explaining the growth method of the GaN layer according to the first embodiment of the present invention.
FIG. 6 is a cross-sectional view for explaining the growth method of the GaN layer according to the first embodiment of the present invention.
FIG. 7 is a cross-sectional view for explaining the growth method of the GaN layer according to the first embodiment of the present invention.
FIG. 8 is a cross-sectional view for explaining the growth method of the GaN layer according to the first embodiment of the present invention.
FIG. 9 shows striped SiO as a growth mask in the GaN layer growth method according to the first embodiment of the present invention;₂It is a SEM photograph of the surface of the c plane sapphire substrate which formed the film.
FIG. 10 shows stripe-shaped SiO as a growth mask in the GaN layer growth method according to the first embodiment;₂It is a SEM photograph of the surface when a GaN layer is grown on a c-plane sapphire substrate on which a film is formed.
FIG. 11 is an SEM photograph of the surface when a GaN layer is grown at a growth temperature of 500 ° C. for comparison with the first embodiment of the present invention.
FIG. 12 is an SEM photograph of the surface when a GaN layer is grown at a growth temperature of 600 ° C. for comparison with the first embodiment of the present invention.
FIG. 13 is a cross-sectional view for explaining the method for manufacturing a GaN-based semiconductor laser according to the third embodiment of the invention.
FIG. 14 is a cross-sectional view for explaining the method for manufacturing a GaN-based semiconductor laser according to the third embodiment of the invention.
FIG. 15 is a cross sectional view for illustrating the method for manufacturing the GaN compound semiconductor laser according to the second embodiment of the invention.
FIG. 16 is a cross-sectional view for explaining a conventional method of growing a GaN layer on a c-plane sapphire substrate.
[Explanation of symbols]
1 ... c-plane sapphire substrate, 2 ... SiO₂3 ... Crystal nucleus, 4 ... GaN layer, 5 ... n-type GaN contact layer, 6 ... n-type AlGaN cladding layer, 7 ... Active layer, 9 ... p-type AlGaN Cladding layer, 10 ... p-type GaN contact layer, 12 ... p-side electrode, 13 ... n-side electrode

Claims (8)

In the method of growing a nitride III-V compound semiconductor, a nitride III-V compound semiconductor is grown on a substrate made of a material different from the nitride III-V compound semiconductor.
In a state where the growth mask formed directly on the substrate, on the substrate at each opening of said growth mask is selectively grown nitride III-V compound semiconductor at a growth temperature of 700 to 800 ° C. above the opening After substantially filling the portion, the nitride III-V compound semiconductor is united by laterally growing the nitride III-V compound semiconductor from each opening at a growth temperature of 950 to 1050 ° C. A method for growing a nitride III-V compound semiconductor characterized in that a continuous film is formed. The shortest distance from an arbitrary point on the surface of the growth mask to the edge of the growth mask is based on the diffusion length of atoms or molecules involved in the growth of the nitride III-V compound semiconductor on the surface of the growth mask. 2. The method of growing a nitride III-V compound semiconductor according to claim 1, wherein the growth mask is formed so as to be smaller . 2. The method for growing a nitride III-V compound semiconductor according to claim 1, wherein the nitride III-V compound semiconductor is GaN, and the width of the growth mask is 3 [mu] m or less . 2. The method for growing a nitride III-V compound semiconductor according to claim 1, wherein the growth mask has a stripe shape . 2. The method for growing a nitride III-V compound semiconductor according to claim 1, wherein the growth mask is made of a dielectric or an insulator . It said growth mask according to claim 1 nitride III-V compound semiconductor method of growth, wherein a made of SiO ₂ or SiN. 2. The method for growing a nitride-based III-V compound semiconductor according to claim 1 , wherein the substrate is a sapphire substrate, a SiC substrate, a Si substrate, or a spinel substrate . In a method for manufacturing a semiconductor device in which a nitride III-V compound semiconductor is grown on a substrate made of a material different from that of a nitride III-V compound semiconductor,
With the growth mask directly formed on the substrate, a nitride III-V compound semiconductor is selectively grown on the substrate at each opening of the growth mask at a growth temperature of 700 to 800 ° C. After substantially filling the portion, the nitride III-V compound semiconductor is united by laterally growing the nitride III-V compound semiconductor from each opening at a growth temperature of 950 to 1050 ° C. To form a continuous film
A method of manufacturing a semiconductor device.

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