Supersonic jet epitaxy of wide band gap semiconductors (Aluminum gallium nitride, Silicon carbide)

Experimental studies are presented concerning the growth of wide band semiconductor thin films on silicon using supersonic jet epitaxy. Hyperthermal precursors are shown to enhance the growth of the compound semiconductors SiC and AlGaN.; Single crystal cubic SiC is grown using a single source organosilicon precursor (methylsilane) at 750°C on 100 mm silicon in a large area growth chamber. Use of a single source precursor deters the formation of voids at the SiC/Si interface. No deposition was observed at temperatures above 1000°C. Arrhenius plot of growth rate as function of growth temperature results in an apparent activation energy of 1.12 eV/mol, which less than half of that in chemical vapor deposition (CVD). This is direct evidence that the growth of SiC from methylsilane at low temperatures is made possible by supersonic jet epitaxy. The increased translational energy of the methylsilane molecules helps to overcome the reaction barrier for direct chemisorption.; Transmission electron microscopy (TEM) is employed to analyze the structural properties of cubic silicon carbide. High resolution cross-sectional TEM images are obtained at the SiC/Si interface and SiC epilayer. Schematic model of twined-SiC/Si interface is given and fit the experimental image accurately. The structures of dislocations, twins, and stacking faults are observed at atomic resolution. TEM results are in agreement with X-ray diffraction (XRD) measurements and reflection high energy electron diffraction (RHEED). TEM results imply that the planar defects originate from three-dimensional growth mode.; Selective area epitaxy of AlGaN and SiC in a small area growth chamber is achieved on patterned silicon substrates with feature sizes of 2 mum and 200 nm, respectively. The surface roughness were found to be unchanged when the growth was confined into smaller region. Crystal quality remains the same for the growth on 2 mum and 200 nm patterned substrates. SiO2 and Si3N4 are employed as masks leading to different selectivity. High growth temperature and low pressure were found to improve the selectivity. It is suggested from the experimental results that selectivity on the mask hinges on the desorption of precursor molecules.