Engineering epitaxial gamma-Al2O3 gate dielectric films on 4H-SiC

• The formation of epitaxial gamma-Al2O3 thin films on 4H-SiC was found to be strongly dependent on the film thickness. An abrupt interface was observed in films up to 200 A thick with an epitaxial relationship of gamma-Al2O3(111)parallel to 4H-SiC(0001) and gamma-Al2O3(4 (4) over bar0)parallel to 4H-SiC(11 (2) over bar0). The in-plane alignment between the film and the substrate is nearly complete for gamma-Al2O3 films up to 115 A thick, but quickly diminishes in thicker films. The films are found to be slightly strained laterally in tension; the strain increases with thickness and then decreases in films thicker than 200 A, indicating strain relaxation which is accompanied by increased misorientation. By controlling the structure of ultrathin Al2O3 films, metal-oxide-semiconductor capacitors with Al2O3 gate dielectrics on 4H-SiC were found to have a very low leakage current density, suggesting suitability of Al2O3 for SiC device integration.

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NATURAL SCIENCES

NATURVETENSKAP

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