Homoepitaxy Of Ge And Growth Of Ge On SGOI Substrates

Ge is one of the promising materials for integrated optoelectronic devices due to its high carrier mobility and large absorption coefficient in the communication band.SGOI materials,which combine the advantages of SOI and SiGe materials,can be used to fabricate high-performance p-MOSFETs and high-speed photodetectors.Therefore,epitaxial growth of high-quality Ge on Ge and SGOI substrates is necessary for its possible application in high performance devices.However,to obtain clean surface of Ge or SGOI substrates is the biggest challenge for further epitaxial layersThis thesis aims to prepare high-quality Ge epitaxial layers on Ge and SGOI substrates.The main research contents include the following two aspects:1.Ge homoepitaxy technique was developed.An approach was proposed to obtain clean Ge surface by ozone oxidation and thermal annealing in vacuum,on which high crystal quality Ge and full strained Sio.21of Geo.79 layers were grown with a low temperature Ge buffer layer.It was found that ozone treatment for an optimized duration could effectively alleviate the formation Ge suboxides on Ge substrate.The fully oxidized GeO2 could be completely removed during the vacuum annealing process to achieve fresh clean surface,which overcame the obstacle for Ge homoepitaxy by UHV/CVD.2.The silicon germanium-on-insulator(SGOI)materials were prepared by modified Ge condensation method and Ge epilayers were successfully grown on the SGOI substrates.High crystal quality SGOI substrate materials with different Ge components were prepared by multi-step temperature gradient Ge condensation method.The gradually decrease of temperature rendered the uniform composition distribution in the SGOI materials.Then,the effect of the cleaning methods of the SGOI substrates with different Ge compositions were studied on epitaxy of Ge layers,and finally,a very flat Ge layer were epitaxially grown on the SGOI substrate with a Ge composition of 0.39.The RMS is only 0.55 nm.