TWI476948B - Epitaxial structure and method for making the same - Google Patents

Description

Epitaxial structure and preparation method thereof

The invention relates to a kind of epitaxial structure and a preparation method thereof.

Epitaxial structures, especially heteroepitaxial structures, are one of the main materials for fabricating semiconductor devices. For example, in recent years, gallium nitride epitaxial wafers for preparing light-emitting diodes (LEDs) have become a research hotspot.

The gallium nitride epitaxial wafer refers to a GaN material molecule which is regularly arranged and oriented on a sapphire substrate under certain conditions. However, the preparation of high-quality GaN epitaxial wafers has been a difficult point of research. Due to the difference in lattice constant and thermal expansion coefficient of gallium nitride and sapphire substrates, there are many dislocation defects in the gallium nitride epitaxial layer. Moreover, there is a large stress between the gallium nitride epitaxial layer and the sapphire substrate, and the greater the stress, the GaN epitaxial layer is broken. This heteroepitaxial structure generally has a lattice mismatch phenomenon, and is easy to form defects such as dislocations.

The prior art provides a method for improving the above-described deficiencies by epitaxially growing gallium nitride using a non-flat sapphire substrate. However, the prior art generally uses a microelectronic process such as photolithography to form a trench on the surface of the sapphire substrate to form a non-planar epitaxial growth surface. The method is not only complicated in process, high in cost, but also pollutes the epitaxial growth surface of the sapphire substrate, thereby affecting the quality of the epitaxial structure.

In view of this, it is necessary to provide a method for preparing an epitaxial structure and a high-quality epitaxial structure which are simple in process, low in cost, and which do not cause contamination on the surface of the substrate.

An epitaxial structure comprising: a substrate having an epitaxial growth surface, and an epitaxial layer formed on the epitaxial growth surface of the substrate, wherein further comprising a carbon nanotube layer disposed on the epitaxial layer and the substrate between.

An epitaxial structure comprising: a substrate having an epitaxial growth surface, and a heteroepitaxial layer formed on the epitaxial growth surface of the substrate, wherein further comprising a patterned carbon nanotube layer disposed on the substrate The heteroepitaxial layer is interposed between the substrate and the substrate, and the patterned carbon nanotube layer has a plurality of openings, such that the plurality of openings of the heteroepitaxial layer penetrating the carbon nanotube layer are in contact with the epitaxial growth surface of the substrate.

A method for preparing an epitaxial structure, comprising the steps of: providing a substrate having an epitaxial growth surface supporting epitaxial layer growth; providing a carbon nanotube layer on an epitaxial growth surface of the substrate; and epitaxial growth on the substrate The growth surface grows an epitaxial layer.

Compared with the prior art, the method for obtaining a patterned mask by providing a carbon nanotube layer on the epitaxial growth surface of the substrate is simple in process and low in cost, and the preparation cost of the epitaxial structure is greatly reduced, and the pair is reduced. Environmental pollution. Further, the epitaxial structure including the carbon nanotube layer makes the epitaxial structure have a wide range of uses.

The epitaxial structure and the preparation method thereof provided by the embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In order to facilitate understanding of the technical solution of the present invention, the present invention first introduces a method for preparing a heteroepitaxial structure.

Referring to FIG. 1 , an embodiment of the present invention provides a method for preparing a hetero-epitaxial structure 10 , which specifically includes the following steps:

S10: providing a substrate 100, and the substrate 100 has an epitaxial growth surface 101 supporting the growth of the heteroepitaxial layer 104;

S20: a carbon nanotube layer 102 is disposed on the epitaxial growth surface 101 of the substrate 100;

S30: The heteroepitaxial layer 104 is grown on the epitaxial growth surface 101 of the substrate 100.

In step S10, the substrate 100 provides an epitaxial growth surface 101 of the heteroepitaxial layer 104. The epitaxial growth surface 101 of the substrate 100 is a molecularly smooth surface, and impurities such as oxygen or carbon are removed. The substrate 100 may be a single layer or a plurality of layers. When the substrate 100 has a single layer structure, the substrate 100 may be a single crystal structure and have a crystal plane as the epitaxial growth surface 101 of the hetero epitaxial layer 104. The material of the single-layer structure substrate 100 may be GaAs, GaN, Si, SOI, AlN, SiC, MgO, ZnO, LiGaO ₂ , LiAlO ₂ or Al ₂ O ₃ or the like. When the substrate 100 has a plurality of layer structures, it is required to include at least one of the above single crystal structures, and the single crystal structure has a crystal face as the epitaxial growth surface 101 of the heteroepitaxial layer 104. The material of the substrate 100 may be selected according to the heteroepitaxial layer 104 to be grown, preferably, the substrate 100 and the heteroepitaxial layer 104 have similar lattice constants and coefficients of thermal expansion. The thickness, size and shape of the substrate 100 are not limited and may be selected according to actual needs. The substrate 100 is not limited to the materials listed above, as long as the substrate 100 having the epitaxial growth surface 101 supporting the growth of the heteroepitaxial layer 104 is within the scope of the present invention.

In step S20, the carbon nanotube layer 102 is a continuous unitary structure including a plurality of carbon nanotubes. A plurality of carbon nanotubes in the carbon nanotube layer 102 extend in a direction substantially parallel to the surface of the carbon nanotube layer 102. When the carbon nanotube layer 102 is disposed on the epitaxial growth surface 101 of the substrate 100, the plurality of carbon nanotubes in the carbon nanotube layer 102 extend in a direction substantially parallel to the epitaxial growth of the substrate 100. Face 101. The carbon nanotube layer has a thickness of from 1 nm to 100 μm, or from 1 nm to 1 μm, or from 1 nm to 200 nm, preferably from 10 nm to 100 nm. The carbon nanotube layer 102 is a patterned carbon nanotube layer 102. The "patterning" means that the carbon nanotube layer 102 has a plurality of openings 105 penetrating the carbon nanotube layer 102 from the thickness direction of the carbon nanotube layer 102. When the carbon nanotube layer 102 covers the epitaxial growth surface 101 of the substrate 100, the portion of the epitaxial growth surface 101 of the substrate 100 corresponding to the opening 105 is exposed to facilitate the growth of the heteroepitaxial layer 104. The opening 105 can be a microhole or a gap. The opening 105 has a size of 10 nm to 500 μm, and the size refers to the aperture of the micro hole or the pitch of the gap in the width direction. The opening 105 has a size of 10 nm to 300 μm, or 10 nm to 120 μm, or 10 nm to 80 μm, or 10 nm to 10 μm. The smaller the size of the opening 105, the less the generation of dislocation defects during the growth of the epitaxial layer is obtained to obtain a high quality heteroepitaxial layer 104. Preferably, the opening 105 has a size of 10 nm to 10 μm. Further, the carbon nanotube layer 102 has a duty ratio of 1:100 to 100:1, or 1:10 to 10:1, or 1:2 to 2:1, or 1:4 to 4:1. . Preferably, the duty ratio is 1:4~4:1. The "duty ratio" refers to the area of the portion of the epitaxial growth surface 101 that is occupied by the carbon nanotube layer 102 and the portion exposed through the opening 105 after the carbon nanotube layer 102 is disposed on the epitaxial growth surface 101 of the substrate 100. ratio.

Further, the "graphical" means that the plurality of carbon nanotubes in the carbon nanotube layer 102 are arranged in an orderly and regular manner. For example, the plurality of carbon nanotubes in the carbon nanotube layer 102 have axial directions substantially parallel to the epitaxial growth surface 101 of the substrate 100 and extend substantially in the same direction. Alternatively, the axial directions of the plurality of carbon nanotubes in the carbon nanotube layer 102 may regularly extend substantially in more than two directions. Alternatively, the plurality of carbon nanotubes in the carbon nanotube layer 102 extend axially along a crystal orientation of the substrate 100 or at an angle to a crystal orientation of the substrate 100. Adjacent carbon nanotubes extending in the same direction in the above-mentioned carbon nanotube layer 102 are connected end to end by Van Der Waals force.

Under the premise that the carbon nanotube layer 102 has the opening 105 as described above, the plurality of carbon nanotubes in the carbon nanotube layer 102 may also be disorderly arranged and randomly arranged.

Preferably, the carbon nanotube layer 102 is disposed on the entire epitaxial growth surface 101 of the substrate 100. The carbon nanotubes in the carbon nanotube layer 102 may be one or a plurality of single-walled carbon nanotubes, double-walled carbon nanotubes or multi-walled carbon nanotubes, and the length and diameter thereof may be as needed select.

The carbon nanotube layer 102 serves as a mask for growing the heteroepitaxial layer 104. By "mask" is meant that the carbon nanotube layer 102 is used to shield a portion of the epitaxial growth surface 101 of the substrate 100 and expose a portion of the epitaxial growth surface 101 such that the heteroepitaxial layer 104 is only exposed from the epitaxial growth surface 101. Part of the growth. Since the carbon nanotube layer 102 has a plurality of openings 105, the carbon nanotube layer 102 forms a patterned mask. After the carbon nanotube layer 102 is disposed on the epitaxial growth surface 101 of the substrate 100, a plurality of carbon nanotubes extend in a direction parallel to the epitaxial growth surface 101. Since the carbon nanotube layer 102 forms a plurality of openings 105 on the epitaxial growth surface 101 of the substrate 100, a patterned mask is formed on the epitaxial growth surface 101 of the substrate 100. It can be understood that, compared with a microelectronic process such as photolithography, the method of epitaxial growth by providing a carbon nanotube layer 102 mask is simple in process, low in cost, and difficult to introduce pollution on the epitaxial growth surface 101 of the substrate 100, and is environmentally friendly. The preparation cost of the heteroepitaxial structure 10 is greatly reduced.

It will be appreciated that the substrate 100 and the carbon nanotube layer 102 together form a substrate for growing a heteroepitaxial structure. The substrate can be used to grow heteroepitaxial layers 104 of different materials, such as semiconductor epitaxial layers, metal epitaxial layers, or alloy epitaxial layers. The substrate can also be used to grow a homoepitaxial layer to provide a homoepitaxial structure.

The carbon nanotube layer 102 may be directly formed on the epitaxial growth surface 101 of the substrate 100 after being formed in advance. The carbon nanotube layer 102 is a macrostructure, and the carbon nanotube layer 102 is a self-supporting structure. By "self-supporting", the carbon nanotube layer 102 does not require a large area of carrier support, but can maintain its own state by simply providing a supporting force on both sides, that is, placing the carbon nanotube layer 102 (or When fixed to two supports disposed at a certain distance apart, the carbon nanotube layer 102 located between the two supports can be suspended to maintain its own state. Since the carbon nanotube layer 102 is a self-supporting structure, the carbon nanotube layer 102 does not have to be formed on the epitaxial growth surface 101 of the substrate 100 by complicated chemical methods. Further preferably, the carbon nanotube layer 102 is a pure carbon nanotube structure composed of a plurality of carbon nanotubes. The term "pure carbon nanotube structure" means that the carbon nanotube layer does not require any chemical modification or acidification treatment throughout the preparation process, and does not contain any functional group modification such as a carboxyl group.

The carbon nanotube layer 102 can also be a composite structure comprising a plurality of carbon nanotubes and an additive material. The additive material includes one or a plurality of graphite, graphite thin, lanthanum carbide, boron nitride, tantalum nitride, cerium oxide, amorphous carbon, and the like. The additive material may further include one or a plurality of metal carbides, metal oxides, metal nitrides, and the like. The additive material is coated on at least a portion of the surface of the carbon nanotube layer 102 in the carbon nanotube layer 102 or in the opening 105 of the carbon nanotube layer 102. Preferably, the additive material is coated on the surface of the carbon nanotube. Since the additive material is coated on the surface of the carbon nanotube, the diameter of the carbon nanotubes becomes large, so that the opening 105 between the carbon nanotubes is reduced. The additive material may be formed on the surface of the carbon nanotube by chemical vapor deposition (CVD), physical vapor deposition (PVD), magnetron sputtering, or the like.

Laying the carbon nanotube layer 102 on the epitaxial growth surface 101 of the substrate 100 may further include an organic solvent treatment step to more closely bond the carbon nanotube layer 102 to the epitaxial growth surface 101. The organic solvent may be selected from a mixture of one or more of ethanol, methanol, acetone, dichloroethane and chloroform. The organic solvent in this embodiment employs ethanol. The step of treating with an organic solvent may immerse the organic solvent on the surface of the carbon nanotube layer 102 through a test tube to infiltrate the entire carbon nanotube layer 102 or immerse the substrate 100 and the entire carbon nanotube layer 102 together with an organic solvent. Infiltrated in the container.

The carbon nanotube layer 102 may also be directly grown on the epitaxial growth surface 101 of the substrate 100 or on the surface of the ruthenium substrate by chemical vapor deposition (CVD) or the like, and then transferred to the epitaxial surface of the substrate 100. Growth face 101.

Specifically, the carbon nanotube layer 102 may include a carbon nanotube film or a nano carbon line. The carbon nanotube layer 102 may be a single-layer carbon nanotube film or a plurality of laminated carbon nanotube films. The carbon nanotube layer 102 can include a plurality of carbon nanotube lines disposed in parallel or a plurality of interdigitated carbon nanotube lines. When the carbon nanotube layer 102 is a plurality of laminated carbon nanotube films, the number of layers of the carbon nanotube film is not too high, and preferably, it is 2 to 100 layers. When the carbon nanotube layer 102 is a plurality of carbon nanotubes arranged in parallel, the distance between adjacent two nanocarbon lines is from 0.1 micrometer to 200 micrometers, preferably from 10 micrometers to 100 micrometers. The space between the adjacent two nanocarbon lines constitutes the opening 105 of the carbon nanotube layer 102. The length of the gap between two adjacent nanocarbon lines may be equal to the length of the nanocarbon line. The carbon nanotube film or the nanocarbon line may be directly laid on the epitaxial growth surface 101 of the substrate 100 to constitute the carbon nanotube layer 102. The size of the opening 105 in the carbon nanotube layer 102 can be controlled by controlling the number of layers of the carbon nanotube film or the distance between the carbon nanotubes.

The carbon nanotube membrane is a self-supporting structure composed of a plurality of carbon nanotubes. The plurality of carbon nanotubes extend in a preferred orientation along the same direction. The preferred orientation means that the majority of the carbon nanotubes in the carbon nanotube film extend substantially in the same direction. Moreover, the overall direction of extension of the majority of the carbon nanotubes is substantially parallel to the surface of the carbon nanotube film. Further, most of the carbon nanotubes in the carbon nanotube film are connected end to end by van der Waals force. Specifically, each of the carbon nanotubes in the majority of the carbon nanotube membranes extending in the same direction and the carbon nanotubes adjacent in the extending direction are connected end to end by van der Waals force. Of course, there are a few randomly arranged carbon nanotubes in the carbon nanotube film, and these carbon nanotubes do not significantly affect the overall orientation of most of the carbon nanotubes in the carbon nanotube film. The self-supporting carbon nanotube film does not require a large-area carrier support, but can maintain a self-membrane state as long as the supporting force is provided on both sides, that is, the carbon nanotube film is placed (or fixed on) When the two supports are disposed at a certain distance apart, the carbon nanotube film located between the two supports can be suspended to maintain the self-membrane state. The self-supporting is mainly achieved by the presence of continuous carbon nanotubes extending through the end-to-end extension of the van der Waals force in the carbon nanotube film.

Specifically, most of the carbon nanotube membranes extending substantially in the same direction in the same direction are not absolutely linear, and may be appropriately bent; or may not be completely aligned in the extending direction, and may be appropriately deviated from the extending direction. Therefore, it is not possible to exclude partial contact between the carbon nanotubes juxtaposed in the majority of the carbon nanotubes extending substantially in the same direction.

Referring to Figures 2 and 3, in particular, the carbon nanotube film comprises a plurality of continuous and oriented extended carbon nanotube segments 143. The plurality of carbon nanotube segments 143 are connected end to end by van der Waals force. Each of the carbon nanotube segments 143 includes a plurality of mutually parallel carbon nanotubes 145 that are tightly coupled by van der Waals forces. The carbon nanotube segments 143 have any length, thickness, uniformity, and shape. The carbon nanotube film can be obtained by directly drawing a part of a carbon nanotube from an array of carbon nanotubes. The carbon nanotube film has a thickness of 1 nm to 100 μm, and the width is related to the size of the carbon nanotube array for taking out the carbon nanotube film, and the length is not limited. There are micropores or gaps between adjacent carbon nanotubes in the carbon nanotube film to form an opening 105, and the pore size or gap size of the micropores is less than 10 micrometers. Preferably, the carbon nanotube film has a thickness of from 100 nm to 10 μm. The carbon nanotubes 145 in the carbon nanotube film extend in a preferred orientation in the same direction. For the structure of the carbon nanotube film and the preparation method thereof, please refer to the patent application "Nano Carbon Tube" of Taiwan No. I327177, which was filed on July 12, 2010 by Fan Shoushan et al. Film structure and preparation method thereof, Applicant: Hon Hai Precision Industry Co., Ltd. In order to save space, only this is cited, but all the technical disclosures of the above application should also be considered as part of the technical disclosure of the present application.

Referring to FIG. 4, when the carbon nanotube layer comprises a plurality of laminated carbon nanotube films stacked in a stack, the extending direction of the carbon nanotubes in the adjacent two layers of carbon nanotube film forms an intersection angle α, And α is greater than or equal to 0 degrees and less than or equal to 90 degrees (0° <= α <= 90°).

In order to reduce the thickness of the carbon nanotube film, the carbon nanotube film may be further heat treated. In order to prevent the carbon nanotube film from being destroyed upon heating, the method of heating the carbon nanotube film adopts a local heating method. Specifically, the method comprises the steps of: locally heating the carbon nanotube film to oxidize a portion of the carbon nanotube film at a local position; and moving the carbon nanotube to be locally heated to realize the entire portion from the local to the whole Heating of the carbon tube film. Specifically, the carbon nanotube film can be divided into a plurality of small regions, and the carbon nanotube film is heated region by region in a partial to integral manner. The method of locally heating the carbon nanotube film may be various, such as laser heating, microwave heating, and the like. In this embodiment, the carbon nanotube film is irradiated by a laser scan having a power density of more than 0.1 × 10 ⁴ watts/m 2 , and the carbon nanotube film is heated from a partial to a whole. The carbon nanotube film is irradiated by laser, and some of the carbon nanotubes are oxidized in the thickness direction, and the carbon nanotube bundle having a larger diameter in the carbon nanotube film is removed, so that the carbon nanotube film is thinned. .

It is to be understood that the above method of scanning the carbon nanotube film is not limited as long as the carbon nanotube film can be uniformly irradiated. The laser scanning can be performed row by row along the arrangement direction of the carbon nanotubes in the parallel carbon nanotube film, or can be performed column by column in the direction perpendicular to the arrangement of the carbon nanotubes in the carbon nanotube film. The smaller the speed of the laser-scanned carbon nanotube film with fixed power and fixed wavelength, the more heat absorbed by the carbon nanotube bundle in the carbon nanotube film, the more the corresponding carbon nanotube bundle is destroyed, after laser treatment The thickness of the carbon nanotube film becomes small. However, if the laser scanning speed is too small, the carbon nanotube film will absorb too much heat and be burned. In this embodiment, the laser power density is greater than 0.053×10 ¹² watts/square meter, the laser spot diameter is in the range of 1 mm to 5 mm, and the laser scanning illumination time is less than 1.8 seconds. Preferably, the laser is a carbon dioxide laser having a power of 30 watts, a wavelength of 10.6 microns, a spot diameter of 3 mm, and a relative movement speed of the laser device 140 and the carbon nanotube film of less than 10 mm/ second.

The nanocarbon line may be a non-twisted nano carbon line or a twisted nano carbon line. The non-twisted nano carbon pipeline and the twisted nanocarbon pipeline are both self-supporting structures. Specifically, referring to FIG. 5, the non-twisted nanocarbon pipeline includes a plurality of carbon nanotubes extending in a direction parallel to the length of the non-twisted nanocarbon pipeline. Specifically, the non-twisted nanocarbon pipeline includes a plurality of carbon nanotube segments, and the plurality of carbon nanotube segments are connected end to end by van der Waals force, and each of the carbon nanotube segments includes a plurality of parallel and pass through each other Derived tightly combined with carbon nanotubes. The carbon nanotube segments have any length, thickness, uniformity, and shape. The non-twisted nano carbon line is not limited in length and has a diameter of 0.5 nm to 100 μm. The non-twisted nano carbon pipeline is obtained by treating the carbon nanotube membrane with an organic solvent. Specifically, an organic solvent is impregnated on the entire surface of the carbon nanotube film, and a plurality of mutually parallel carbon nanotubes in the carbon nanotube film pass through the surface tension generated by the volatilization of the volatile organic solvent. The van der Waals force is tightly combined to shrink the carbon nanotube film into a non-twisted nanocarbon line. The organic solvent is a volatile organic solvent such as ethanol, methanol, acetone, dichloroethane or chloroform, and ethanol is used in this embodiment. The non-twisted nanocarbon line treated by the organic solvent has a smaller specific surface area and a lower viscosity than the carbon nanotube film which is not treated with the organic solvent.

The twisted nanocarbon line is obtained by twisting both ends of the carbon nanotube film in opposite directions by a mechanical force. Referring to FIG. 6, the twisted nanocarbon pipeline includes a plurality of carbon nanotubes extending axially around the twisted nanocarbon pipeline. Specifically, the twisted nanocarbon pipeline includes a plurality of carbon nanotube segments, and the plurality of carbon nanotube segments are connected end to end by van der Waals force, and each of the carbon nanotube segments includes a plurality of parallel and pass through each other Derived tightly combined with carbon nanotubes. The carbon nanotube segments have any length, thickness, uniformity, and shape. The twisted nanocarbon line is not limited in length and has a diameter of 0.5 nm to 100 μm. Further, the twisted nanocarbon line can be treated with a volatile organic solvent. Under the action of the surface tension generated by the volatilization of the volatile organic solvent, the adjacent carbon nanotubes in the treated twisted nanocarbon pipeline are tightly bonded by van der Waals to make the specific surface area of the twisted nanocarbon pipeline Decrease, increase in density and strength.

The nano carbon pipeline and the preparation method thereof can be referred to the application of Fan Shoushan et al. on November 5, 2002, and the Taiwan Patent No. I303239 announced on November 27, 2008, "a nano carbon tube rope and its "Manufacturing Method", Applicant: Hon Hai Precision Industry Co., Ltd., and Application No. I312337, announced on December 21, 2009, Taiwan Patent Publication "Nano Carbon Tube Manufacturing Method", Application Person: Hon Hai Precision Industry Co., Ltd. In order to save space, only this is cited, but all the technical disclosures of the above application should also be considered as part of the technical disclosure of the present application.

In step S30, the growth method of the heteroepitaxial layer 104 may be performed by molecular beam epitaxy (MBE), chemical beam epitaxy (CBE), vacuum deuteration, low temperature epitaxy, selective epitaxy, liquid deposition epitaxy ( One of LPE), metal organic vapor phase epitaxy (MOVPE), ultra-vacuum chemical vapor deposition (UHVCVD), hydride vapor phase epitaxy (HVPE), and metal organic chemical vapor deposition (MOCVD) or Multiple implementations.

The hetero-epitaxial layer 104 refers to a single crystal structure grown by epitaxial growth on the epitaxial growth surface 101 of the substrate 100, the material of which is different from the substrate 100, so that the heteroepitaxial layer 104 is referred to. The thickness of the growth of the heteroepitaxial layer 104 can be prepared as needed. Specifically, the thickness of the heteroepitaxial layer 104 may be from 0.5 nm to 1 mm. For example, the thickness of the heteroepitaxial layer 104 can be from 100 nanometers to 500 micrometers, or from 200 nanometers to 200 micrometers, or from 500 nanometers to 100 micrometers. The hetero- epitaxial layer 104 may be a semiconductor epitaxial layer, and the material of the semiconductor epitaxial layer is GaMnAs, GaAlAs, GaInAs, GaAs, SiGe, InP, Si, AlN, GaN, GaInN, AlInN, GaAlN or AlGaInN. The hetero- epitaxial layer 104 may be a metal epitaxial layer, and the material of the metal epitaxial layer is aluminum, platinum, copper or silver. The hetero- epitaxial layer 104 may be an alloy epitaxial layer, and the material of the epitaxial layer of the alloy is MnGa, CoMnGa or Co ₂ MnGa.

Referring to FIG. 7 , specifically, the growth process of the hetero epitaxial layer 104 specifically includes the following steps:

S31: nucleation and epitaxial growth along a direction substantially perpendicular to the epitaxial growth surface 101 of the substrate 100 to form a plurality of heteroepitaxial crystal grains 1042;

S32: the plurality of heteroepitaxial crystal grains 1042 are epitaxially grown along a direction substantially parallel to the epitaxial growth surface 101 of the substrate 100 to form a continuous heteroepitaxial film 1044;

S33: The heteroepitaxial film 1044 is epitaxially grown along a direction substantially perpendicular to the epitaxial growth surface 101 of the substrate 100 to form a heteroepitaxial layer 104.

In step S31, the plurality of heteroepitaxial grains 1042 are grown at a portion of the epitaxial growth surface 101 of the substrate 100 exposed through the opening 105 of the carbon nanotube layer 102, and the growth direction thereof is substantially perpendicular to the substrate. The epitaxial growth surface 101 of 100, that is, the plurality of heteroepitaxial crystal grains 1042 in this step is longitudinally epitaxially grown.

In step S32, the plurality of heteroepitaxial crystal grains 1042 are homogenously epitaxially grown and integrated in a direction substantially parallel to the epitaxial growth surface 101 of the substrate 100 by controlling growth conditions to integrate the carbon nanotube layer 102. cover. That is, in the step, the plurality of heteroepitaxial crystal grains 1042 are directly merged into the lateral epitaxial growth, and finally a plurality of holes 103 are formed around the carbon nanotubes to surround the carbon nanotubes. Preferably, the carbon nanotubes are spaced apart from the heteroepitaxial layer 104 surrounding the carbon nanotubes. The shape of the holes is related to the arrangement direction of the carbon nanotubes in the carbon nanotube layer 102. When the carbon nanotube layer 102 is a single-layer carbon nanotube film or a plurality of parallel disposed nanocarbon lines, the plurality of holes 103 are substantially parallel grooves. When the carbon nanotube layer 102 is a plurality of layers of carbon nanotube film or a plurality of intersecting carbon nanotubes, the plurality of holes 103 are intersecting groove networks.

In step S33, due to the presence of the carbon nanotube layer 102, lattice dislocations between the heteroepitaxial crystal grains 1042 and the substrate 100 stop growing during the formation of the continuous heteroepitaxial film 1044. Therefore, the heteroepitaxial layer 104 of this step corresponds to homoepitaxial growth on the surface of the heteroepitaxial film 1044 having no defects. The heteroepitaxial layer 104 has fewer defects. In the first embodiment of the present invention, the substrate 100 is a sapphire (Al 2 O 3 ) substrate, and the carbon nanotube layer 102 is a single-layer carbon nanotube film. This embodiment uses an MOCVD process for epitaxial growth. Among them, high-purity ammonia (NH3) is used as the source gas of nitrogen, hydrogen (H2) is used as the carrier gas, and trimethylgallium (TMGa) or triethylgallium (TEGa) or trimethylindium (TMIn) is used. Trimethylaluminum (TMAl) is used as a Ga source, an In source, and an Al source. Specifically, the following steps are included. First, the sapphire substrate 100 is placed in a reaction chamber, heated to 1100 ° C to 1200 ° C, and passed through H 2 , N 2 or a mixed gas thereof as a carrier gas, and baked at a high temperature for 200 seconds to 1000 seconds. Secondly, continue to carry the same carrier gas, and cool down to 500 ° C ~ 650 ° C, through the introduction of trimethyl gallium or triethyl gallium and ammonia, grow GaN low temperature buffer layer, the thickness of 10 nm ~ 50 nm. Then, the passage of trimethylgallium or triethylgallium is stopped, and the ammonia gas and the carrier gas are continuously supplied, and the temperature is raised to 1100 ° C to 1200 ° C, and the temperature is maintained for 30 seconds to 300 seconds for annealing. Finally, the temperature of the substrate 100 is maintained at 1000 ° C ~ 1100 ° C, and the ammonia gas and the carrier gas are continuously introduced, and trimethylgallium or triethylgallium is re-introduced, and the lateral epitaxial growth process of GaN is completed at a high temperature. And a high quality GaN epitaxial layer is grown. After the sample was grown, the samples were observed and tested by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), respectively. Referring to FIG. 8 and FIG. 9, in the heteroepitaxial structure prepared in this embodiment, the heteroepitaxial layer grows only from the position where the epitaxial growth surface of the substrate has no carbon nanotube layer, and then is integrated. The surface of the heteroepitaxial layer in contact with the substrate forms a plurality of holes, and the carbon nanotube layer is disposed in the hole and spaced apart from the heteroepitaxial layer. Specifically, it can be clearly seen from FIG. 8 that the interface between the GaN epitaxial layer and the sapphire substrate is seen, wherein the dark portion is a GaN epitaxial layer and the light portion is a sapphire substrate. The surface of the GaN epitaxial layer in contact with the sapphire substrate has a row of holes. As can be seen from Fig. 9, a carbon nanotube is disposed in each of the holes. The carbon nanotubes in the holes are disposed on the surface of the sapphire substrate and spaced apart from the GaN epitaxial layer forming the holes.

Referring to FIG. 10 and FIG. 11 , a hetero-epitaxial structure 10 prepared by the first embodiment of the present invention includes: a substrate 100, a carbon nanotube layer 102 and a hetero-epitaxial layer 104. The substrate 100 has an epitaxial growth surface 101. The carbon nanotube layer 102 is disposed on the epitaxial growth surface 101 of the substrate 100. The carbon nanotube layer 102 has a plurality of openings 105, and the epitaxial growth surface 101 of the substrate 100 corresponds to the carbon nanotube layer A portion of the opening 105 of 102 is exposed. The hetero epitaxial layer 104 is disposed on the epitaxial growth surface 101 of the substrate 100 and covers the carbon nanotube layer 102. The carbon nanotube layer 102 is disposed between the heteroepitaxial layer 104 and the substrate 100.

The heteroepitaxial layer 104 covers the carbon nanotube layer 102 and penetrates the plurality of openings 105 of the carbon nanotube layer 102 to contact the epitaxial growth surface 101 of the substrate 100, that is, the nanocarbon The heteroepitaxial layer 104 is infiltrated into a plurality of openings 105 of the tube layer 102. The heteroepitaxial layer 104 and the covered carbon nanotube layer 102 are microscopically spaced apart, that is, the surface of the heteroepitaxial layer 104 in contact with the substrate 100 forms a plurality of holes 103, and the carbon nanotube layer 102 is disposed on In the hole 103, specifically, the carbon nanotubes in the carbon nanotube layer 102 are respectively disposed in the plurality of holes 103. The holes 103 are formed on a surface of the heteroepitaxial layer 104 that is in contact with the substrate 100, and the holes 103 are blind holes in the thickness direction of the heteroepitaxial layer 104. Within each of the holes 103, the carbon nanotubes are substantially not in contact with the heteroepitaxial layer 104.

The carbon nanotube layer 102 is a self-supporting structure. The carbon nanotube layer comprises a carbon nanotube membrane or a nanocarbon pipeline. In this embodiment, the carbon nanotube layer 102 is a single-layer carbon nanotube film, and the carbon nanotube film includes a plurality of carbon nanotubes. The axial directions of the plurality of carbon nanotubes are in the same direction. The preferred orientation extends, and the adjacent carbon nanotubes extending in the same direction are connected end to end by van der Waals force. Micropores or gaps are provided at intervals between adjacent carbon nanotubes perpendicular to the direction of extension to form openings 105.

Referring to FIG. 12, a hetero-epitaxial structure 20 prepared according to a second embodiment of the present invention includes a substrate 200, a carbon nanotube layer 202, and a hetero-epitaxial layer 204. The material of the substrate 200 and the heteroepitaxial layer 204 of the heteroepitaxial structure 20 in the second embodiment of the present invention, and the positional relationship between the substrate 200, the carbon nanotube layer 202 and the heteroepitaxial layer 204, and the heteroepitaxial structure of the first embodiment 10 is substantially the same, except that the carbon nanotube layer 202 is a plurality of parallel and spaced carbon nanotube lines, and micropores are formed between adjacent nano carbon lines.

The nanocarbon line may be a non-twisted nano carbon line or a twisted nano carbon line. Specifically, the non-twisted nanocarbon pipeline includes a plurality of carbon nanotubes extending along the length of the non-twisted nanocarbon pipeline. The twisted nanocarbon pipeline includes a plurality of carbon nanotubes extending axially around the twisted nanocarbon pipeline.

In the second embodiment of the present invention, the substrate 100 is a silicon-on-insulator (SOI) substrate, and the carbon nanotube layer 102 is a plurality of parallel and spaced carbon nanotubes. This embodiment uses an MOCVD process for epitaxial growth. Among them, trimethylgallium (TMGa) and trimethylaluminum (TMAl) are used as the source materials of Ga and Al, ammonia (NH3) is used as the source of nitrogen, hydrogen (H2) is used as carrier gas, and horizontal level is used. The furnace is heated. Specifically, a plurality of parallel and spaced carbon nanotube lines are first laid on the epitaxial growth surface 101 of the SOI substrate 100. Then, a GaN epitaxial layer is epitaxially grown on the epitaxial growth surface 101 of the substrate 100, a growth temperature of 1070 ° C, a growth time of 450 seconds, mainly performing longitudinal growth of GaN; then maintaining the pressure of the reaction chamber unchanged, raising the temperature to 1110 ° C, while reducing Ga The source flow rate was maintained while maintaining the ammonia gas flow rate to promote lateral epitaxial growth with a growth time of 4,900 seconds. Finally, the temperature was lowered to 1070 ° C while increasing the Ga source flow rate and continuing longitudinal growth for 10,000 seconds.

Referring to FIG. 13, a third embodiment of the present invention provides a hetero-epitaxial structure 30 including a substrate 300, a carbon nanotube layer 302, and a hetero-epitaxial layer 304. The material of the substrate 300 and the heteroepitaxial layer 304 of the heteroepitaxial structure 30 in the third embodiment of the present invention, and the positional relationship between the substrate 300, the carbon nanotube layer 302 and the heteroepitaxial layer 304, and the heteroepitaxial structure of the second embodiment 20 is substantially the same, except that the carbon nanotube layer 302 is a plurality of intersecting and spaced-apart nanocarbon pipelines, and micropores are formed between the intersecting and adjacent four nanocarbon pipelines. Specifically, the plurality of nanocarbon pipelines are respectively disposed in parallel with the second direction along the first direction, and the first direction is disposed to intersect with the second direction. An opening is formed between the four nano carbon lines that are crossed and adjacent. In this embodiment, two adjacent nanocarbon pipelines are arranged in parallel, and the two nanocarbon pipelines intersecting each other are perpendicular to each other. It can be understood that the nano carbon pipeline can also be disposed in any crossover manner, and only the carbon nanotube layer 302 is formed into a plurality of openings, so that the epitaxial growth surface portion of the substrate 300 is partially exposed.

The hetero-epitaxial structure 30 of the third embodiment of the present invention can be produced by the same method as the first embodiment or the second embodiment.

A fourth embodiment of the present invention provides a homoepitaxial structure comprising: a substrate, a carbon nanotube layer, and an epitaxial layer. The carbon nanotube layer in the fourth embodiment of the present invention may adopt the carbon nanotube layer of the first to third embodiments, the material and the positional relationship between the substrate, the carbon nanotube layer and the epitaxial layer, and the first The embodiments are substantially identical except that the substrate is of the same material as the epitaxial layer to form a homoepitaxial structure. Specifically, in this embodiment, the material of the substrate and the epitaxial layer is GaN.

The fourth embodiment of the present invention further provides a method for preparing a homoepitaxial structure, which specifically includes the following steps:

S100: providing a substrate, and the substrate has an epitaxial growth surface supporting growth of a homoepitaxial layer;

S200: providing a carbon nanotube layer on the epitaxial growth surface of the substrate, the substrate and the carbon nanotube layer together forming a substrate;

S300: growing a homoepitaxial layer on the epitaxial growth surface of the substrate.

The method for growing a homoepitaxial layer of the fourth embodiment of the present invention is substantially the same as the method for growing a heteroepitaxial layer of the first embodiment, except that the substrate and the material of the epitaxial layer are the same, thereby constituting a homoepitaxial structure.

The present invention uses a carbon nanotube layer as a mask to be disposed on the epitaxial growth surface epitaxial layer of the substrate to have the following effects:

First, the carbon nanotube layer is a self-supporting structure, which can be directly laid on the epitaxial growth surface of the substrate, and the mask is formed by a process such as post-deposition lithography with respect to the prior art. The process of the invention is simple, low in cost, and advantageous. In mass production.

Secondly, the carbon nanotube layer is a patterned structure, and the thickness and the opening size thereof can reach a nanometer level, and the heteroepitaxial crystal grains formed when the substrate is used to grow the epitaxial layer have a smaller size, which is advantageous. To reduce the generation of dislocation defects to obtain a high quality heteroepitaxial layer.

Third, the opening size of the carbon nanotube layer is nanometer, and the epitaxial layer is grown from the exposed epitaxial growth surface corresponding to the nano-scale opening, so that the contact area between the grown epitaxial layer and the substrate is reduced. Small, the stress between the epitaxial layer and the substrate during the growth process is reduced, so that a heterogeneous epitaxial layer having a larger thickness can be grown, and the quality of the heteroepitaxial layer can be further improved.

In summary, the present invention has indeed met the requirements of the invention patent, and has filed a patent application according to law. However, the above description is only a preferred embodiment of the present invention, and it is not possible to limit the scope of the patent application of the present invention. Equivalent modifications or variations made by persons skilled in the art in light of the spirit of the present invention are intended to cover the scope of the following claims.

10,20,30. . . Hetero-epitaxial structure

100,200,300. . . Base

101. . . Epitaxial growth surface

102,202,302. . . Carbon nanotube layer

103. . . Hole

104,204,304. . . Hetero epitaxial layer

1042. . . Hetero-epitaxial grain

1044. . . Hetero epitaxial film

105. . . Opening

143. . . Carbon nanotube fragment

145. . . Carbon nanotube

FIG. 1 is a process flow diagram of a method for preparing a heteroepitaxial structure according to an embodiment of the present invention.

2 is a scanning electron micrograph of a carbon nanotube film used in an embodiment of the present invention.

3 is a schematic view showing the structure of a carbon nanotube segment in the carbon nanotube film of FIG. 2.

4 is a scanning electron micrograph of a carbon nanotube film disposed at a plurality of layers in an embodiment of the present invention.

Figure 5 is a scanning electron micrograph of a non-twisted nanocarbon pipeline used in an embodiment of the present invention.

Figure 6 is a scanning electron micrograph of a twisted nanocarbon line employed in an embodiment of the present invention.

FIG. 7 is a schematic view showing a growth process of a heteroepitaxial layer in an embodiment of the present invention.

Figure 8 is a scanning electron micrograph of a cross section of a heteroepitaxial structure prepared in accordance with a first embodiment of the present invention.

Figure 9 is a transmission electron micrograph at the interface of the heteroepitaxial structure prepared in the first embodiment of the present invention.

FIG. 10 is a schematic perspective structural view of a hetero-epitaxial structure according to a first embodiment of the present invention.

Figure 11 is a cross-sectional view of the heteroepitaxial structure shown in Figure 10 taken along line XI-XI.

FIG. 12 is a schematic perspective structural view of a hetero-epitaxial structure according to a second embodiment of the present invention.

FIG. 13 is a schematic perspective structural view of a hetero-epitaxial structure according to a third embodiment of the present invention.

10. . . Hetero-epitaxial structure

100. . . Base

101. . . Epitaxial growth surface

102. . . Carbon nanotube layer

103. . . Hole

104. . . Hetero epitaxial layer

105. . . Opening

Claims (36)

A method for preparing an epitaxial structure, comprising the steps of:
Providing a substrate having an epitaxial growth surface supporting epitaxial layer growth;
A carbon nanotube layer is disposed on the epitaxial growth surface of the substrate; and an epitaxial layer is grown on the epitaxial growth surface of the substrate. The method for preparing an epitaxial structure according to claim 1, wherein the epitaxial layer is a heteroepitaxial layer. The method for preparing an epitaxial structure according to claim 2, wherein the substrate is a single crystal structure, and the material of the substrate is GaAs, GaN, Si, SOI, AlN, SiC, MgO, ZnO. , LiGaO ₂ , LiAlO ₂ or Al ₂ O ₃ . The method for preparing an epitaxial structure according to claim 2, wherein the method of disposing a carbon nanotube layer on the epitaxial growth surface of the substrate is to directly lay a carbon nanotube film or a nano carbon pipeline. The epitaxial growth surface of the substrate serves as a carbon nanotube layer. The method for preparing an epitaxial structure according to claim 2, wherein the carbon nanotube layer has a plurality of openings, and the portion of the heteroepitaxial layer exposed from the epitaxial growth surface of the substrate through the opening Growing. The method for preparing an epitaxial structure according to claim 2, wherein the method for growing the heteroepitaxial layer specifically comprises the following steps:
Nucleating and epitaxially growing along a direction substantially perpendicular to an epitaxial growth surface of the substrate to form a plurality of heteroepitaxial grains;
The plurality of heteroepitaxial grains are epitaxially grown along a direction substantially parallel to an epitaxial growth surface of the substrate to form a continuous heteroepitaxial film; and the heteroepitaxial film is oriented along an epitaxial growth surface substantially perpendicular to the substrate Epitaxial growth forms a heteroepitaxial layer. The method for preparing an epitaxial structure according to the second aspect of the invention, wherein the method for growing the epitaxial layer comprises a molecular beam epitaxy method, a chemical beam epitaxy method, a vacuum deuteration method, a low temperature epitaxy method, a selective epitaxy method, and a liquid One or more of phase deposition epitaxy, metal organic vapor phase epitaxy, ultra-vacuum chemical vapor deposition, hydride vapor phase epitaxy, and metal organic chemical vapor deposition. The method for preparing an epitaxial structure according to claim 2, wherein the heteroepitaxial layer forms a plurality of holes around the carbon nanotube layer to form a carbon nanotube in the carbon nanotube layer. Surrounded. The method for preparing an epitaxial structure according to claim 1, wherein the epitaxial layer is a homoepitaxial layer. An epitaxial structure comprising: a substrate having an epitaxial growth surface, and an epitaxial layer formed on the epitaxial growth surface of the substrate, the improvement comprising further comprising a carbon nanotube layer disposed on the epitaxial layer Between the base and the base. The epitaxial structure according to claim 10, wherein the epitaxial layer is a heteroepitaxial layer. The epitaxial structure according to claim 11, wherein the carbon nanotube layer is a self-supporting structure directly laid on an epitaxial growth surface of the substrate. The epitaxial structure according to claim 11, wherein the carbon nanotube layer has a plurality of openings, and the heteroepitaxial layer covers the opening of the carbon nanotube layer and penetrates the opening of the carbon nanotube layer Contacting the epitaxial growth surface of the substrate. The epitaxial structure according to claim 13, wherein the opening has a size of 10 nm to 500 μm. The epitaxial structure according to claim 14, wherein the opening has a size of 10 nm to 120 μm. The epitaxial structure according to claim 15, wherein the opening has a size of 10 nm to 80 μm. The epitaxial structure according to any one of claims 14 to 16, wherein the carbon nanotube layer has a duty ratio of 1:100 to 100:1. The epitaxial structure according to any one of claims 14 to 16, wherein the carbon nanotube layer has a duty ratio of 1:4 to 4:1. The epitaxial structure according to claim 11, wherein the heteroepitaxial layer forms a plurality of holes in a surface in contact with the substrate, and the carbon nanotube layer is disposed in the hole. The epitaxial structure according to claim 11, wherein the carbon nanotube layer has a thickness of from 1 nm to 100 μm. The epitaxial structure according to claim 11, wherein the carbon nanotube layer comprises at least one carbon nanotube film, the carbon nanotube film comprises a plurality of carbon nanotubes, and the plurality of carbon nanotubes The axial direction of the carbon nanotubes extends in a preferred orientation in the same direction. The epitaxial structure according to claim 21, wherein the adjacent carbon nanotubes extending in the preferred direction in the same direction are connected end to end by van der Waals force. The epitaxial structure according to claim 21, wherein the carbon nanotube layer comprises a plurality of carbon nanotube film laminates. The epitaxial structure of claim 11, wherein the carbon nanotube layer comprises a plurality of parallel and spaced carbon nanotubes. The epitaxial structure of claim 11, wherein the carbon nanotube layer comprises a plurality of cross-set nano carbon pipelines. The epitaxial structure according to claim 24 or 25, wherein the nano carbon line has a diameter of 0.5 nm to 100 μm, and the distance between two adjacent parallel carbon nanotube lines is 0.1. Micron ~ 200 microns. The epitaxial structure according to claim 11, wherein the epitaxial layer is a semiconductor epitaxial layer, a metal epitaxial layer or an alloy epitaxial layer. The epitaxial structure according to claim 11, wherein the substrate is a single crystal structure, and the material of the substrate is GaAs, GaN, Si, SOI, AlN, SiC, MgO, ZnO, LiGaO ₂ , LiAlO ₂ or Al ₂ O ₃ . The epitaxial structure according to claim 11, wherein the carbon nanotube layer is a continuous unitary structure. The epitaxial structure according to claim 11, wherein the carbon nanotube layer comprises a plurality of carbon nanotubes extending in a direction parallel to a surface of the carbon nanotube layer. The epitaxial structure according to claim 11, wherein the carbon nanotube layer is a composite structure comprising a plurality of carbon nanotubes and an additive material. The epitaxial structure according to claim 31, wherein the additive material is one or a plurality of graphite, graphite thin, lanthanum carbide, boron nitride, tantalum nitride, cerium oxide, and amorphous carbon. The epitaxial structure according to claim 31, wherein the additive material is one or a plurality of metal carbides, metal oxides, and metal nitrides. The epitaxial structure according to claim 31, wherein the carbon nanotube layer has a plurality of openings, and the additive material is coated on at least a part of the surface or the surface of the carbon nanotube layer of the carbon nanotube layer. Inside the opening of the carbon nanotube layer. The epitaxial structure according to claim 10, wherein the epitaxial layer is a homoepitaxial layer. An epitaxial structure comprising: a substrate having an epitaxial growth surface, and a heteroepitaxial layer formed on the epitaxial growth surface of the substrate, the improvement comprising further comprising a patterned carbon nanotube layer disposed on The heteroepitaxial layer is interposed between the heteroepitaxial layer and the substrate, and the patterned carbon nanotube layer has a plurality of openings, such that the plurality of openings of the heteroepitaxial layer penetrating the carbon nanotube layer are in contact with the epitaxial growth surface of the substrate.