Investigation On InGaN Alloy Growth By MBE And Its Photoconductivity Behavior

High-quality material preparation is essential for the development of basic disciplines and device preparation.In order to realize the epitaxial growth of high-quality nitride materials,it is necessary to continuously explore the material growth kinetics and thermodynamics rules,and provide guiding guidelines for the device structure design.In this paper,the whole component InxGa1-xN was prepared by MBE method,and then the epitaxial growth of InGaN was further studied under the influence of the droplet,and the transport characteristics under the light were studied.1.Through the MBE temperature control method,the growth of whole component InGaN thin films was achieved.RHEED and AFM results showed that the growth of InxGai-xN with low In and extremely high In components were 2-D layer by layer growth model,while the intermediate components showed 3-D growth pattern.The XRD result indicates that the crystal quality of InxGai-xN shows the trend of improving firstly after deterioration with the increase In the In component,which is related to the alloy disorder of InxGai-xN material.The alloy in the intermediate In component InxGai-xN film is the most disordered,so the crystal quality is the worst.2.The "microplate" structure of the surface induced by In droplets was studied.In order to explain the formation process of microstructure,we propose a new growth model,in which a droplet is a kind of close to the edge of the vapor-liquid-solid three phase coexistence system,interface to minimum,make InxGa1-xN fastest growth within the system,and In itself can be used as a catalyst,stimulating the growth of IncGa1-xN,thus formed the "micro dish"structure.The EDS analysis showed that In content in the region covered by the droplet was higher,and the formation of the droplets In the growth process increased the local ?/? ratio,leading to the increase of the In component..3.Using ?-RDS to investigate the stress field uniformity of InGaN thin film under the droplets.The results show that the RD image of "microplate" shows a four-polarity distribution,and the model calculation derivation shows that this quatemity distribution only occurs when the stress field is evenly distributed,that is,the source of the RD signal is only the "microplate"The height of the border fluctuates.4.The transport properties of InxGa1-xN thin film with different In compositions were systematically studied under light at room temperature.It was found that there was a critical In composition xc(xc = 0.7).When the In composition x exceeded 0.7,InxGa1-xN exhibited negative photoconductivity,while the In composition x was lower than xc,InxGa1-xN exhibits positive photoconductivity.Through the establishment of energy band model,a point defect energy level ER related to In is proposed.The density of recombination center determines the type of photoconduction.The recombination center formed by such point defects captures holes under illumination,and the positively charged recombination center acts as a scattering center for the electrons due to the Coulomb potential,lowering the mobility of the material and further affecting the change in the conductivity.