Investigation Of The Growth Mechanism And Structural Defects For Semi-Polar AlN Growth By HVPE

The semi-polar Aluminum nitride(AlN)is an ideal material for applications in various deep-UV optoelectronic devices,high-power and highfrequency electronic devices.Recent developments in hydride vapor phase epitaxy(HVPE)growth of high-quality thick AlN crystals made it possible for thick and freestanding(FS)AlN substrates to be manufactured.However,there are still various difficulties in the study of semi-polar AlN growth: the surface control due to anisotropy in the growth of semi-polar surface materials;how to quickly calculate the dislocation densities and the basal stacking faults in semipolar AlN films by high-resolution X-ray diffraction,and so on.In view of the current research hotspots and difficulties,this paper adopted the self-developed high temperature HVPE growth system to explore the influence of HVPE growth conditions on high-quality semi-polar AlN single crystal.At the same time,we studied the types of defects inside semi-polar AlN,explored the method of reducing the defect density of semi-polar AlN,revised the W-Hall dislocation calculation formula.A rapid calculation method was proposed to evaluate the density of the dislocations in semi-polar(11-22)AlN films by HRXRD,achieving the following results:1.The first principles theory calculation method was used to model and calculate the different crystal planes of AlN materials.Through the analysis of the surface energy of the exposed surfaces,it was theoretically confirmed that the surface energy of the(11-22)crystal plane is the higher among the many semi-polar planes of AlN.In the continuous corrosion experiment,we also obtained experimental results on the stable existence of(11-22)crystal planes under specific corrosion conditions,confirming the relatively high stability performance of(11-22)crystal planes.2.The semi-polar(11-22)AlN was grown on home-made horizontal HVPE.Respectively from those aspects to explore: the miscut of substrate,the buffer layer,the nitriding layer,the annealing of sputter film,the temperature,the pressure and the V/III rate.The 2-in high-quality(11-22)AlN thick film was obtained with a thickness of 8.5 μm.3.Due to the complexity of defect types,there is no accurate calculation method suitable for dislocation density in the research of semi-polar Ⅲ nitrides.The only method was using expensive transmission electron microscopy for sample destructive analysis.To solve this problem,we improved the semi-polar plane analogy on the basis of Mosaic growth model,modified the W-Hall dislocation calculation formula,and proposed a method to measure and calculate the density of dislocations in(11-22)AlN film by HRXRD.The method also had potential application to other semi-polar planes in group-III nitrides.The experiment confirmed that this method is consistent with the analysis of defect density by transmission electron microscopy,and this method has been granted an invention patent.4.Because of the complex defect types and distribution in semi-polar AlN materials,the transmission electron microscope was used for systematic observation and classification,and the defect types and distribution in semipolar AlN were summarized.We explored methods for reducing defect density and discovered the evolution mechanism for eliminating defects in high-quality(11-22)AlN.Besides,an effective method to rapidly obtain high-quality(11-22)AlN thick film was proposed.