Growth And Characterization Of GaAs And SiGe Film On Si Substrate

Silicon-based optoelectronics integration and semiconductor quantum computing both are popular and frontier research areas.Silicon-based light source is the core subject of silicon-based photo-electronics integration.The epitaxy of the III-V group light emitting material with direct band gap on a silicon substrate compatible with the CMOS process is one of the best solutions for silicon-based light source integration.There are three challenges with the epitaxial growth III-V group material on the silicon substrate:antiphase domain,lattice mismatch and thermal crack.In the field of semiconductor quantum computing,electronic spin quantum bits are prepared based on strain silicon quantum well with high mobility.Silicon has a weak nuclear spin and electron spin orbit coupling,and nature Si and Ge can be purified to eliminate nuclear spin,easy to obtain longer spin relaxation time and quantum decoherence time.Based on the high-mobility strained Ge quantum well,we can fabricate hole spin quantum bit,the hole spin is less susceptible to the effects of nuclear spin than electron spin,and the period of decoherence is long.The spin is strongly coupled with orbit,and can be operated by electron dipole spin resonance.In order to obtain a high-mobility strained silicon and strained Ge quantum well sandwiched by Si Ge film,we need to acquire Si_0.7Ge_0.3 film and Si_0.2Ge_0.8 film that are low-dislocations density and high-flatness by molecular beam epitaxy.The three works presented in this dissertation are epitaxial growth and characterization of high-quality gallium arsenide film,Si_0.7Ge_0.3 film and Si_0.2Ge_0.8film based on Si.The first chapter of the dissertation introduces two major research backgrounds,the basic knowledge of material growth and dislocation characterization related to the research.The second chapter describes the instruments and equipment used in the experiment,including molecular beam epitaxy system and the preparation of transmission electron microscope samples.The third chapter,at first,I reviewed the methods of epitaxial growth of gallium arsenide film on silicon substrate reported in the past paper,and then proposes a new method.The saw-tooth hollow structure with{113}crystal faces is constructed by depositing the Ge on the patterned Si(001)substrate.Combined with XRD,TEM and AFM analysis,it is proved that the structure can effectively solve the problem of lattice mismatch and antiphase domain,and effectively alleviate the problem of thermal mismatch.The optimized gallium arsenide film's threading dislocation density can be reduced to a magnitude of10⁶/cm².The In As/Ga As quantum dots based on gallium arsenide film that is only400 nm thick on the{113}faceted saw-tooth hollow structure show high-efficiency PL intensity.The fourth chapter firstly summarizes the Si_0.7Ge_0.3 film growth method needed for growth strained silicon in chronological order,and then proposes a new method to grow Si_0.7Ge_0.3 film.Experimentally,the method of rapid and non-destructive threading dislocation and stacking fault characterization by atomic force microscope was established.Through low temperature growth,combined with the strain field of the superlattice structure,enhance the slip of dislocation,while we fabricated patterned Si to terminate the dislocations,and finally obtained the threading dislocations density of Si_0.7Ge_0.3 film on the patterned Si from 10⁸/cm² to 10⁶/cm²,the root mean square roughness of film is 0.1-0.2 nm or so.Based on the Si_0.75Ge_0.25 film and Si_0.7Ge_0.3 film provided by the Institute of Microelectronics of the Chinese Academy of Sciences,we improved the mobility of strained Si to 3.12×10⁵cm²/Vs.The fifth chapter of the dissertation summarizes the Si_0.2Ge_0.8 film growth method and introduces a new way to grow Ge film on Si substrate.Based on the high-quality Ge film,the effect of different quality of Ge film and different reverse gradient rate on Si_0.2Ge_0.8film quality was compared.The current Si_0.2Ge_0.8 film threading dislocations density is 10⁷/cm².Finally,the thesis concluded with a summary and thanks.The main innovations and research achievements of this dissertation are as below:1.A new method is designed to realize the epitaxy of gallium arsenide film on the silicon substrate compatible with the CMOS process.By constructing a saw-tooth hollow structure consisting of{113}crystal facets on the patterned silicon substrate,combined with transmission electron microscope characterization and electron channeling contrast imaging,it is proved that the structure can effectively solve the problem of lattice mismatch,and the atomic resolution of Ga element and As element is realized by combining spherical aberration corrected transmission electron microscope plus image processing,The annihilation of the antiphase domain boundary proves that the structure can effectively solve the problem of antiphase domain,and the strain analysis of the Ge interlayer and the 400 nm gallium arsenide layer is realized through the high-resolution three-axis crystal reciprocal space mapping,and proves that the structure can effectively alleviate the problem of thermal cracks.Through optimization,a high-quality gallium arsenide film with a 10⁶/cm²threading dislocation density was obtained.2.Realized the epitaxy of high-quality Si_0.7Ge_0.3 thin film on the patterned silicon substrate.Using the strain superlattice layer and the patterned substrate,the Si_0.7Ge_0.3film with a threading dislocation density of 10⁶/cm² and a flatness of less than 0.3nm was finally obtained.Experimentally,an empirical method of rapid and non-destructive characterization of films using atomic force microscopes was established.3.High-quality strained Si for two-dimensional electron gas.Based on the Si_0.75Ge_0.25 film and Si_0.7Ge_0.3 film provided by the Institute of Microelectronics of the Chinese Academy of Sciences,the low temperature mobility of strain silicon that is3.12×10⁵cm²/Vs was obtained,filling the gap of domestic high-mobility strain silicon quantum well.4.Realized the epitaxy of high-quality and high-flatness Ge/Si film.The threading dislocations density of the Ge film is 10⁶/cm²,and the surface root mean square roughness can be controlled below 0.4 nm.Based on the Ge film,the threading dislocations density of Si_0.2Ge_0.8 film obtained is 10⁷/cm²,the surface roughness is less than 1nm.Surface roughness is lower than the results of current papers reported.