PEMOCVD Method With RHEED In Situ Monitoring And Low Temperature Growth Of GaN Based Films

GaN-based III group nitrides are the best candidates for manufacturing LED and LD in the range from blue to ultraviolet and other opto-electronic devices, they also suit for manufacturing high-temperature?high-frequency and high power electronic or microwave devices, because of their excellent properties such as wide band gap, high electron saturation drift velocity, low dielectric constant, high thermal conductivity, good chemical and thermal stability, and so on. In usual MOCVD for growing GaN with ammonia as nitrogen source, people have to grow GaN under high temperature (over 1000@) in order to effectively pyrolyse ammonia. However, during the high temperature growth of GaN-based film materials, a mass of nitrogen hollow space will be resulted in the films due to the high decomposition pressure of nitrogen and quick volatilization of nitrogen, then the GaN film has very high background electron concentration, and the p-type doping is very difficult to achieve. So, the high temperature is a main impediment to grow good quality of metastable cubic GaN.Fristly. an active nitrogen source at low temperature must be obtained in order to reduce growth temperature. Nitrogen plasma as nitrogen source for heteroepitaxy growth of GaN-based III group nitride films at low temperature on GaAs(OOl), Si(OOl) and a -A12O3(0001) substrates by ECR-PEMOCVD is presented in this thesis. Additionally, the initial nucleation, the processing and mechanism of material growth, and the results detected in situ by RHEED during the growth of GaN-based III group nitride films are investigated. The major work and conclusions are as follows:1. Based on synthetical analysis of the advantages and defects of ESPD equipment. as a major participator , we successfully developed a super-high vacuum equipment ESPD-U with RHEED in situ monitoring equipment, and our national invention patent -#Electron cyclotron resonance microwave plasma enhance MOCVD epitaxy system and method$ has been publicized. The growth of various mono-element and multi-element compound semiconductor films can be realized on ESPD-U, especially the control growth for complex sandwich and super-thin film microstructure semiconductor materials with in situ detection of mono-atom layer level can be realized. The surface appearance of epitaxy layer and microstructure information of growth surface can be detected in situ by RHEED. It benefits to optimize the growth processing of thin film, especially to optimize the initial growth processing which is very important for heteroepitaxy on substrates with big misfit of crystal lattice. So the investigation and developing periods for growing new type semiconductor thin film materials by MOCVD can be greatly shortened. Furthermore, the correlative basic research, such as the interaction between plasma and growing surface, can be carried out on ESPD-U also.2. Experiment results demonstrated that the cavity coupling-magnetic multipole ECR plasma source (MEP source) can produce large area uniform and steady ECR plasma with higher microwave-plasma coupling efficiency (94%), high density, high ionization, low ion energy (<2eV) and low space potential (30V). It has an advantage to control and reduce werfer damage, owing to the ion energy and space voltage are very low, so MEP source is very adequate for growing semiconductor thin film and etching without damage, etc. And the investigation of plasma emission spectra indicated that ECR source has very strong activation function.3. The crystal lattice constant of growing surface in different processes, such as cleaning and nitridation of substrate, growth of GaN and A1N epilayer, could be measured through RHEED from different incidence direction. So the strain state of surface could be analyzed. According to the crystal lattice constant of growing surface is inversely proportioned to the space of RHEED stripes and using standard value 4.758 A of lattice constant of a -Al2O3(000l) surface (as) as a scale of demarcation, the lattice spacing of epilayer surface was measured indir...