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Pseudomorphic Semiconducting Heterostructures from Combinations of AIN, GaN and Selected SiC Polytypes: Theoretical Advancement and its Coordination with Experimental Studies of Nucleation, Growth, Characterization and Device Development.
Semiannual Technical rept. 1 Jul-31 Dec 94,
NORTH CAROLINA STATE UNIV AT RALEIGH DEPT OF MATERIALS SCIENCE AND ENGINEERING
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Beta3C-SiC nucleation and 2H-SiC step flow growth have been achieved on 2H-AlN thin 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 SiCAlN 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 substratefilm and the filmfilm 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 GaN001 films were grown on sapphire0001 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 4.5micronshr were achieved. The films had a columnar morphology. jg
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