Growth And Characterization Of Low-defect AlN And GaN-based Materials

Ⅲ-nitride materials have excellent properties,and the devices prepared therefrom are widely used both in the field of lighting,communication and detecting lasers.Ⅲ-nitride materials cannot be prepared by pulling method as the Si single crystal,but the preparation of high-quality Ⅲ-group nitride materials is always the base of application.In recent years,there have been many studies on the epitaxial growth of low-defect Ⅲ-nitride materials.In order to reduce the defect dislocation density,the researchers used some effective growth methods: lateral epitaxial growth,patterned substrate epitaxial growth,etc.,but these methods use mostly micron-scale graphics,epitaxial growth on micro-patterned The required growth temperature is higher,and the combined thickness of the pattern is higher which is difficult to achieve for many group Ⅲ nitride materials,especially AlN materials.Epitaxial growth on nano-patterning can make up for the above shortcomings.There are few studies on epitaxial growth of group Ⅲ-nitride materials on nanopatterning,especially lacking the internal mechanism analysis.In order to find a better epitaxial growth method for preparing a group Ⅲ-nitride materials.In this paper,nano-patterning is selected as the research focus,and a new epitaxial growth method is introduced to epitaxially grow low-defect Ⅲ-nitride materials on nanopatterning.Two methods are mainly used to prepare nano-patterning: the self-organization of Nanosphere mask preparation nano-patterning used to GaN overgrowth,electron beam exposure method to prepare nano-patterning used to AlN overgrowth.The main results are as follows:1)The study of the coating process of single-layer nanospheres.GaN substrate can obtain good hydrophilicity by treated in oxygen plasma.Self-assembled nanospheres are arranged more closely at the gas-liquid interface by adding SDS surfactants.Thus,a more uniform and compact single-layer self-assembled nanosphere film can be obtained by pulled.2)The study of the self-organization of different diameters nanosphere mask preparation nano-patterning used to GaN overgrowth.First,we fabricated self-assembled monolayer silica nanospheres with diameters of 300 nm,400 nm,and 500 nm on GaN substrate.Etch depth set to 3000?.Finally,epitaxial overgrowth.The result show that FWHM of the(102)and(002)of the epitaxially grown GaN are decreased compared to the epitaxially grown GaN on a planar sapphire substrate.In the three-size nanospheres,when the nanospheres with a diameter of 500 nm are used as a mask,the GaN(002)plane FWHM decreased from 270 arcsec to 248 arcsec,and the(102)plane FWHM decreased from 390 arcsec to 236 arcsec.3)The study of Preparation Nano-patterning by Electron Beam Lithography.We mainly studied the process flow of electron beam lithography,the design of lithography mask,the design of nano-patterns,and ICP etching to get the theoretical nano-pattern we designed.4)Over-growth of AlN on arrayed circular aperture nanopatterning.We design circular array with a diameter of 300 nm and a pattern period of 600 nm.The epitaxial growth of AlN continues on nanopatterned AlN,and the epitaxial growth temperature is 1050℃,which is much lower than the previous study of 1300℃.The XRD test results show,the FWHM of the(102)plane of the epitaxial AlN is reduced from 890 arcsec to 470 arcsec,while the FWHM of the(002)plane is relatively increased.The proportion of edge dislocations in the AlN crystal is larger,which is in connection with the half height and width of the(102)plane,so the overall dislocation density is reduced.5)The experimental results yield three defect reduction mechanisms: First,lateral epitaxial growth in nanoscale graphical mode.Second,the dislocation bending induces termination at the local medium interface.Third,residual nanopores provide an additional dislocation reduction mechanism.