| Aluminum nitride(AlN),an ultra-wide band gap semiconductor material with many excellent photoelectric properties and stability,is very suitable for the preparation of ultraviolet(UV)optoelectronic,high power and microwave radio frequency devices,which have bright prospects in the fields of UV detection,fifth generation(5G)wireless communication and national defense industry etc.At present,due to the lack of AlN homogeneous substrates,most AlN crystals are mainly epitaxially prepared on silicon carbide(SiC),silicon(Si)and other substrates in a heteroepitaxial manner.However,due to lattice mismatch and thermal mismatch,heteroepitaxial AlN crystals often have a large number of defects,which affect the performance of subsequent devices.Graphene is a two-dimensional carbon nanomaterial with hexagonal honeycomb lattice composed of carbon atoms with sp2 hybrid orbitals,which it’s unique electrical,optical,and mechanical properties have attracted widespread attention after it’s come out.Van der Waals epitaxy(vdWE)does not need to satisfy the lattice matching between the grown crystal and the underlying two-dimensional material,thereby improving the crystal quality and simplifying the epitaxial process.The van der Waals epitaxial growth of AlN on graphene can reduce the effects of lattice mismatch and thermal mismatch caused by traditional heteroepitaxial growth,and improve the crystal quality.Moreover,due to the weak Van der Waals interaction between AlN and the substrate,AlN will be allowed to peel from graphene and transfer to other heterogeneous substrates,leaving behind a clean substrate for reuse.In addition,due to the unavoidable presence of C,O,Si and other elements in the epitaxial environment,leading to doping of impurities during the growth process,conducting a series of optical properties research on AlN is helpful to comprehensively understand the process and behavior of doping and its influence on the semiconductor material structure and the properties,which is of great significance to improve the quality of crystals and optimize the growth craft of material.Therefore,it is of great significance to study the van der Waals epitaxial growth of AlN on graphene and its optical properties,which not only provides new ideas for the preparation of high crystal quality AlN materials,but also opens the way for high quality AlN devices in the future.In this paper,the AlN nanorods was grow on a graphene/SiC substrate via hydride vapor phase epitaxy(HVPE).The growth characteristics and optical characteristics of AlN nanorods on graphene were studied.We use scanning electron microscope(SEM)and transmission electron microscope(TEM)to study the microstructure and its defects.The diameter of AlN nanorods is 520±100 nm and the height is 5.2±0.2 μm.All nanorods grew along the c-axis direction,and no obvious defects such as grain boundaries,stacking faults,dislocations were observed at the interface;Energy dispersive X-ray spectrometer(EDX)shows that the element boundary is obvious at the interface,the thickness of the graphene layer is about 5 nm,and the AlN nanorods are easily peeled from the substrate mechanically,thereby confirming that it is nucleated and grown on the graphene.The optical properties of AlN nanorods were further studied systematically.The cryogenic temperature Raman system was used to study its unltra-low strain(<0.1%)and the temperature dependence of the raman characteristic peak;We successfully excited the deep UV intrinsic peak of 208 nm and the UV defect peak of～361 nm at room temperature combining with the photoluminescence(PL)and the cathodeluminescence(CL).In addition,we preliminary analyzed the relationship between the defect peaks in AlN nanorods and C and O impurities during growth. |
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