Pseudomorphic Semiconducting Heterostructures from Combinations of AIN, GaN andSelected SiC Polytypes: Theoretical Advancement and its Coordination with Experimental Studies of Nucleation, Growth, Characterization and Device Development

摘要

Beta(3C)-SiC nucleation and 2H-SiC step flow growth have been achieved on 2H-AlNthin film templates using gas-source (GS) MBE and C2H4/ Si2H6 gas flow ratios of 1 and 5, respectively. In addition, thin epitaxial films of AlN and SiC/AlN multilayers have been grown by plasma-assisted, GSMBE at 1050 deg C using Si2H6, C2H4 and N2. RHEED and high-resolution TEM revealed monocrystalline layers and pseudomorphic interfacial relationships at the substrate/film and the film/film interfaces. X-ray rocking curve measurements on the (0002) Bragg peak of the AlN films indicate they are the highest quality ever reported. Auger spectroscopy, TEM and electron energy loss spectroscopy have been used to show that the solid solublilty between AlN and SiC is very limited below 1950 deg C. Results regarding the high temperature growth and the use of graded buffer layers for optimizing the microstructural quality of GaN grown by ECR-assisted GSMBE is also reported. The use of supersonic jets (SSJ) to produce GaN thin films has also been incorporated into this program. Highly oriented wurtzite GaN(001) films were grown on sapphire(0001) in the temperature range of 500 deg C to 650 deg C by SSJ. The film growth was controlled by the decomposition rate of NH3. Growth rates as high as 4.5microns/hr were achieved. The films had a columnar morphology. jg.