Nonequilibrium growth of wide-band-gap semiconductors

Experimental studies are presented concerning the growth of wide band semiconductor thin films on silicon using a non-equilibrium growth technique. The technique employed for deposition is supersonic jet epitaxy. The significance of supersonic jet epitaxy lies in its ability to control precursor flux and incident kinetic energy independently.; Hyperthermal precursors are shown to enhance the growth of the compound semiconductors SiC, AlN, and GaN. Single crystal cubic SiC was grown using a single source organosilicon precursor (methylsilane) at the lowest reported temperature to date (600°C). Use of a single source precursor blocks the formation of voids at the SiC/Si interface, which results in a reduced leakage current when the films are biased. Attempts at depositing SiC from an effusive beam of methylsilane were unsuccessful. No deposition was observed at temperatures up to 900°C. 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. We have also demonstrated the ability of supersonic jets to reduce the temperature for SiC film growth by compensating with an increase in methylsilane kinetic energy.; GaN, AlN, and AlGaN film properties (growth rate, crystallinity, optical properties, surface morphology, etc.) were also found to be highly dependent on incident precursor energy and substrate orientation. Crystal quality of the III-N films was found to depend very strongly on growth temperature but only weakly on precursor energy. This would indicate that the chemical reaction on the surface is driven by the precursor energy but the ordering of the crystal is driven by the substrate temperature. This is not surprising for a multi-beam process as surface diffusion is expected to play a more important role than in the case of growth from a single precursor.