Study On MOCVD Growth Of InAlN Ternary Alloy Material

InAlN ternary alloy material is an ideal material for preparing high electron mobility transistors(HEMT),and its a-axis lattice constant is continuous between In N a-axis lattice constant(0.3533 nm)and Al N a-axis lattice constant(0.3112 nm)Adjustable,and when the In composition is 17%,it can be matched with the GaN a-axis lattice constant(0.3189 nm),which can be used to prepare lattice-matched InAlN HEMT devices,which improves the performance and performance of electronic devices,especially high-frequency millimeter wave devices.Reliability provides greater possibilities.However,there are challenges in the epitaxial growth of high-quality InAlN materials.InAlN is composed of two binary materials,In N and Al N,and the lattice constant difference between In N and Al N is large(0.0421 nm),which makes InAlN material have a large miscibility gap,and it is prone to phase separation and compositional differences during growth.Phenomenon such as uniformity.In addition,there is a big difference between the optimal epitaxial growth of In N and Al N,and metal organic chemical vapor deposition(MOCVD)growth of In N materials requires low temperature and high V/III ratio.The opposite is true for Al N materials,whose MOCVD growth requires high temperature and low V/III ratio.Therefore,the epitaxial growth window of InAlN material is narrow.To achieve the epitaxial growth of high-quality InAlN materials,it is necessary to conduct a detailed study of its growth kinetics.In order to grasp the kinetic regulation of the epitaxial growth of InAlN materials,this thesis carried out the MOCVD epitaxial growth research of InAlN materials.The specific research content is as follows:1.Study on InAlN film composition control.The research results show that there is still a large amount of Ga incorporation during the growth process of InAlN without the access to the Ga source.We analyzed the source of Ga atoms and the mechanism of unintentional incorporation,and then achieved the epitaxial growth of pure InAlN films by eliminating residual Ga in the reaction chamber.On this basis,the influence of growth kinetics on the composition of InAlN films was systematically studied.The experimental results show that increasing the growth temperature,growth pressure and reducing the V/III ratio are beneficial to the incorporation of In atoms in the InAlN film.Through the regulation of growth parameters,the epitaxial growth of InAlN thin films in the range of 3.7%to 18.4%In composition was achieved.We analyzed the influence of growth conditions on the composition of InAlN from the perspective of growth kinetics.2.Study on the surface morphology of InAlN film.The influence of growth temperature,pressure and V/III ratio on the surface morphology of InAlN films was systematically studied.The experimental results show that the surface roughness of the InAlN film will gradually decrease with the increase of temperature.We believe that this is related to the decrease of the growth rate of InAlN film and the decrease of In composition caused by the increase of the growth temperature.In addition,the surface morphology of the InAlN film will improve with the decrease of growth pressure and V/III ratio.We believe this is related to the increase in the lateral migration rate of atoms under the conditions of low pressure and low V/III ratio.Through the optimization of the growth process,we achieved the epitaxial growth of an InAlN film with a smooth surface,with a root mean square roughness of 0.65 nm in an area of 2×2?m~2.