A kind of semi-polarity AlN templateTechnical field
The present invention is more particularly directed to a kind of semi-polarity AlN templates, belong to materials science field.
Background technique
The AlN of hexagonal wurtzite structure and its forbidden band of alloy cover the ultraviolet spectral range of 200~365nm, are systemsThe ideal material of standby deep ultraviolet light electrical part and Deep trench termination.However, AlN sill is generally along polar axis-cAxis direction growth, so that AlN and its alloy have very strong piezoelectricity and spontaneous polarization in [0001] direction.This polarizationEffect can generate the built in field of higher-strength in nitride epitaxial layer, cause band curvature, inclination, electrons and holes is made to existIt is spatially separated, greatly reduces the luminous efficiency of AlN base photoelectric device.Therefore people attempt to reduce by various means and polarizeElectric field improves luminescent device performance.Wherein semi-polarity material due to its built in field and growth axis direction it is not parallel, Ke YixianIt lands and reduces polarity effect, therefore obtained extensive concern.
Current top-quality semi-polarity AlN material is to be scaled off from c into AlN thick film.However, with this methodThe size of the AlN material of acquisition is very limited, this forces researcher to begin trying in the different of the non-face c such as sapphire, silicon carbideExtension semi-polarity AlN material on matter substrate, but this technical difficulty is heavy, and the crystalline quality of AlN is very poor, dislocation density veryHeight seriously constrains the efficiency of AlN base photoelectric device.
Summary of the invention
The main purpose of the present invention is to provide a kind of semi-polarity AlN templates, to overcome deficiency in the prior art.
For realization aforementioned invention purpose, the technical solution adopted by the present invention includes:
The embodiment of the invention provides a kind of semi-polarity AlN templates, appear face with semi-polarity, and includeTwin structure orTwin structure.
Further, the semi-polarity AlN template includes: and is formed in AlN substrate to appear on faceTwin knotStructure orTwin structure, the AlN substrate is [0001] orientation, and appears face and beOrAndIt is formed in describedTwin structure orOn twin structure,The AlN material of orientation.
Further, the AlN substrate is formed on substrate.
Further, the substrate includes Sapphire Substrate, such as is preferably c surface sapphire, but not limited to this.
Further, the substrate includes SiC substrate.
Further, describedTwin structure orZigzag is formed between twin structure and AlN substrateInterface.
Further, the section of the AlN substrate is isosceles triangle, when the base angle of the triangle is 51 °~71 °When, AlN is formed in the waist of triangleTwin structure.
Further, the section of the AlN substrate is isosceles triangle, when the base angle of the triangle is 22 °~42 °When, AlN is formed in the waist of triangleTwin structure.
The embodiment of the invention also provides a kind of methods for preparing semi-polarity AlN template comprising: in being grown on substrateAlN, and induce and generate AlNTwin structure orTwin structure is changed into the orientation of growth of AlNAnd then obtain semi-polarity AlN template.
In some embodiments, the method for the preparation semi-polarity AlN template includes:
Growth on substrate forms the AlN substrate of [0001] orientation, and make the AlN substrate appears faceOr
The continued growth AlN on the AlN substrate, and form AlNTwin structure or AlNTwin knotStructure is changed into the orientation of growth of AlN
Further, the section of the AlN substrate is isosceles triangle, when about 61 ° or so of the base angle of the triangle,AlN is formed in the waist of triangleTwin structure.
Further, the section of the AlN substrate is isosceles triangle, when about 32 ° or so of the base angle of the triangle,AlN is formed in the waist of triangleTwin structure.
In some embodiments, the method for the preparation semi-polarity AlN template includes: to be placed in c surface sapphire substrateIn hydride gas-phase epitaxy equipment, with HCl and NH3Make reaction gas, H2And N2For carrier gas, be arranged growth temperature be 1200 DEG C~1600 DEG C, deposition forms the AlN substrate being orientated with a thickness of [0001] of 300nm~3 μm, and make the AlN substrate appears faceForOr
Compared with prior art, beneficial effects of the present invention at least that:
(1) semi-polarity AlN template of the invention can directly select c surface sapphire or SiC etc. to be formed as substrate, withoutR surface sapphire is wanted, can not only reduce the fault in AlN epitaxial layer, and low in cost, and there is better quality.
(2) preparation method of semi-polarity AlN template of the invention can reduce the fault in AlN epitaxial layer, and byThe induction of AlN early growth period generatesOrTwin structure can be such that the orientation of growth of AlN is changed by [0001]ForThis makes that growth window is more wide in range, growth conditions is easier to control, while only needing one step growth, without changing lifeElongate member can make subsequent AlN keep edgeThe growth of semi-polarity direction, so as to avoid secondary pollution, is conducive to obtainObtain the semi-polarity AlN template of high quality.
Detailed description of the invention
Fig. 1 a is 2 θ of XRD/ω scanning figure of obtained AlN thick film in one embodiment of the invention；
Fig. 1 b is the TEM sectional view of obtained AlN thick film in one embodiment of the invention；
Fig. 1 c is the selective electron diffraction figure of serrated layer shown in Fig. 1 b；
Fig. 1 d and Fig. 1 e are the selective electron diffraction figure of crystal column A, B respectively；
Fig. 2 a is the enlarged drawing of serrated layer and prismatic layer interface in one embodiment of the invention；
Fig. 2 b is the selective electron diffraction figure of serrated layer and prismatic layer left and right side interface in one embodiment of the invention；
Fig. 2 c is the high resolving electron diffraction figure on right side interface shown in Fig. 2 b；
Fig. 2 d is the high resolving electron diffraction figure in left side interface shown in Fig. 2 b；
Fig. 3 is ECS in one embodiment of the invention (Equilibrium Crystal Shape) illustraton of model；
Fig. 4 a is 2 θ of XRD/ω scanning of the AlN thick film of laterally overgrown in SiC substrate in another embodiment of the present inventionFigure；
Fig. 4 b is the section the TEM picture of AlN thick film；
Fig. 4 c- Fig. 4 d is respectively the selective electron diffraction and high-resolution transmitted electron image at left side interface；
Fig. 4 e- Fig. 4 f is respectively the selective electron diffraction and high resolving electron diffraction picture at right side interface；
Fig. 5 a is the section picture of AlN thick film；
Fig. 5 b is 2 θ of XRD/ω scanning figure of AlN thick film；
Fig. 5 c- Fig. 5 d is respectively the selective electron diffraction figure at left and right side interface；
Fig. 5 e is the high resolving electron diffraction picture at interface between triangle and crystal column；
Fig. 6 a- Fig. 6 b is to pass through respectivelyTwin realizes the schematic diagram of semi-polarity AlN growth.
Specific embodiment
To facilitate the understanding of the present invention, a more comprehensive description of the invention is given in the following sections with reference to the relevant attached drawings.In attached drawingGive better embodiment of the invention.But the present invention can be realized by many different forms, however it is not limited underEmbodiment described in face.On the contrary, the purpose of providing these embodiments is that making to the disclosure understandingIt is more thorough and comprehensive.
Unless otherwise defined, all technical and scientific terms used herein and belong to technical field of the inventionThe normally understood meaning of technical staff is identical.Term as used herein in the specification of the present invention is intended merely to description toolThe purpose of the embodiment of body, it is not intended that in the limitation present invention.Term as used herein "and/or" includes one or moreAny and all combinations of relevant listed item.
A kind of preparation method for semi-polarity AlN template that an exemplary embodiments of the invention provide, comprising:
(1) 2 inches of c surface sapphire substrate is placed in HVPE (hydride gas-phase epitaxy) equipment, with HCl and NH3Make reaction gas, H2And N2For carrier gas.
(2) setting growth temperature is 1200 DEG C~1600 DEG C, first the AlN base of [0001] orientation of deposition 300nm~3 μmThe face that appears of material, the AlN substrate isOr
(3) if the section of above-mentioned AlN substrate is isosceles triangle, if the base angle of triangle is 61 ° or so, in triangleWaist forms AlNTwin structure；If the base angle of triangle is 32 ° or so, AlN is formed in the waist of triangleTwin structure.
(4) no matter the characteristic that can change crystal growth orientation based on twin is formed any twin according to geometrical relationshipCrystalline substance, the orientation of growth of AlN can be changed intoContinued growth is obtained with semi-polarity AlN mould on this basisPlate.
It please refers to Fig. 1 a- Fig. 1 d, in the embodiment of the present invention, in c to the AlN thick film of grown on sapphire, passes throughTwin growth mode, the orientation of growth are transformed by initial [0001]Wherein, Fig. 1 a is the AlN thick2 θ of XRD of film/ω scanning figure, Fig. 1 b are the TEM sectional views of the AlN thick film, it can be seen that AlN thick film include serrated layer andPrismatic layer.Fig. 1 c is the selective electron diffraction figure of serrated layer shown in Fig. 1 b.Fig. 1 d and Fig. 1 e are the Selected area electron of crystal column A, B respectivelyDiffraction pattern.
The enlarged drawing that Fig. 2 a is serrated layer and prismatic layer interface in the present embodiment is please referred to again.Fig. 2 b is in the present embodimentThe selective electron diffraction figure of serrated layer and prismatic layer left and right side interface, the two interfaces areTwin boundary.Fig. 2 c isThe high resolving electron diffraction picture on right side interface shown in Fig. 2 b, illustrate be hereinCoherence twin boundary.Fig. 2 d is Fig. 2 b instituteShow left side interface high resolving electron diffraction picture, illustrate be hereinNon- coherence twin boundary.
In the present invention, leading to the key point of crystal growth orientation transition isThe formation of twin boundary.Due toTwin boundary beAppear and formed on face, therefore generates first layer serrated layer and be necessary.This processIn, the surface free energy of crystal face is related with growth temperature, for example, the surface free energy of some crystal face is as follows:
Wherein γ (m, T) is the surface free energy of unit area, it is the function of temperature T and crystal orientation m.
It please refers to Fig. 3 and shows the evolutionary process that crystal growth varies with temperature.Wherein, for raw on c surface sapphireLong AlN, when growth temperature is sufficiently high, the surface free energy of (0001) crystal face is minimum, therefore becomes and appear face.At a temperature ofWhen drop, the surface free energy of crystal face can decline.If growth temperature reduces to a certain extent,Crystal faceSurface free energy can be lower thanCrystal face.Although showing that crystal grain is still grown along [0001] direction at this time, it appearsFace has no longer been (0001) crystal face.In particular, in the present embodiment, when growth temperature is lower than 1390 DEG C,Crystal faceReplace (0001) crystal face to become and appears face.The practical growth temperature of this sample is 1300 DEG C, is lower than 1390 DEG C of critical value.It please refers toA-d shows ECS in the present embodiment (Equilibrium Crystal Shape) model in Fig. 3.In the Fig. 3, a, which is shown, to be worked asWhen growth temperature is sufficiently high, AlN is grown along [0001] direction, and appearing face is (0001) crystal face, and b is shown when growthWhen temperature reduces, other crystal faces gradually replace (0001) and show as face, c is appeared when temperature is lower than 1390 DEG C,Crystal face, which becomes, appears face, and d is shownAppear and forms on the basis of faceTwin boundary.
In turn, if AlN continuesAppear and grown on face, the direction c be no longer along z to.Obviously, if it is subsequentCrystal changes the orientation of growth, certainly will will form high-angle boundary, and this will dramatically increase the energy of crystal.With common Grain-Boundary PhaseThan the energy of twin boundary is considerably lower.In fact, the energy of coherence twin boundary only has the 1/10 of common crystal boundary energy, non-coherenceThe energy of twin boundary is the 1/2 of common crystal boundary energy.Therefore, existCrystal can be made by appearing formation twin boundary on faceEnergy keeps minimum, to keep crystal most stable.Possible twin structure has in buergerite systemWithTwin.Appear existing for for faceThe formation of twin provides the foundation.Preferably, existAppear and is formed on faceTwin plane can both make crystal keep minimum energy, maintain stable structure, also fullThe existing geometrical condition of foot.
In another embodiment of the invention, aforementioned Sapphire Substrate also can be replaced SiC substrate.Please referring to Fig. 4 a is this2 θ of XRD of the AlN thick film of laterally overgrown/ω scanning figure on sic substrates in embodiment, shows the sample while including(0001) andCrystal orientation.Fig. 4 b shows the section the TEM picture of AlN thick film；Fig. 4 c- Fig. 4 d is respectively the choosing at left side interfaceArea's electronic diffraction and high-resolution transmitted electron image；Fig. 4 e- Fig. 4 f is respectively the selective electron diffraction and high-resolution electricity at right side interfaceSub- diffraction image, two interfaces areTwin boundary.Fig. 5 a is the cross-sectional image of the obtained AlN thick film of the present embodiment.Fig. 5 b2 θ of XRD/ω scanning figure of the AlN thick film, show in the sample simultaneously containing (0001) andCrystal orientation.Fig. 5 c-Fig. 5 d is respectively the selective electron diffraction image at left and right side interface, and illustrate to be initially formed isTwin boundary.Fig. 5 e isThe high resolving electron diffraction picture at interface, further explanation form between triangle and crystal columnCoherence twin boundary.
Method provided by the invention by making AlN generate twin structure, using twin structure there is change crystal growth to takeTo characteristic, pass through respectively refering to shown in Fig. 6 a- Fig. 6 bTwin realizes semi-polarity AlN growthSchematic diagram.When occurring in AlNOrAfter twin structure, the orientation of growth of AlN is changed by [0001] naturallyForKeep growth conditions constant, it is subsequent both to obtainThe semi-polarity AlN template of orientation, and can be avoidedMultistep growth is polluted caused by sample.Also, the growth course can directly select the face c blue without expensive r surface sapphireJewel is low in cost, help to obtain the semi-polarity AlN template of high quality.
In order to make the foregoing objectives, features and advantages of the present invention clearer and more comprehensible, above in conjunction with attached drawing to the present inventionSpecific embodiment be described in detail.Elaborate many details in the above description in order to fully understand this hairIt is bright.But the present invention can be implemented with being much different from other way described above, those skilled in the art can be notSimilar improvement is done in the case where violating intension of the present invention, therefore the present invention is not limited by particular embodiments disclosed above.AndAnd each technical characteristic of embodiment described above can be combined arbitrarily, for simplicity of description, not in above-described embodimentThe all possible combination of each technical characteristic be all described, if however, there is no contradiction in the combination of these technical features,It all should be considered as described in this specification.From the foregoing, it is to be appreciated that coming for those of ordinary skill in the artIt says, without departing from the inventive concept of the premise, a plurality of modification and improvement can also be made, these belong to guarantor of the inventionProtect range.Therefore, the scope of protection of the patent of the invention shall be subject to the appended claims.