Engineering Epitaxial Gamma-Al-2O-3 Gate Dielectric Films on 4H-SiC

• Published in: Journal of applied physics 2009-04, Vol.102 (10)
• Main Authors: Tanner, C.M., /UCLA, Toney, M.F., /SLAC, SSRL, Lu, J., Blom, H.O., /Uppsala U., Sawkar-Mathur, M., Tafesse, M.A., Chang, J.P.
• Format: Article
• Language: English
• Subjects: ALIGNMENT; CAPACITORS; DIELECTRIC MATERIALS; ENG; LEAKAGE CURRENT; MATERIALS SCIENCE; RELAXATION; STRAINS; SUBSTRATES; THICKNESS; THIN FILMS
• ISSN: 0021-8979; 1089-7550

The formation of epitaxial {gamma}-Al{sub 2}O{sub 3} 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 {angstrom} thick with an epitaxial relationship of {gamma}-Al{sub 2}O{sub 3}(111) {parallel} 4H-SiC(0001) and {gamma}-Al{sub 2}O{sub 3}(4{bar 4}0) {parallel} 4H-SiC(11{bar 2}0). The in-plane alignment between the film and the substrate is nearly complete for {gamma}-Al{sub 2}O{sub 3} films up to 115 {angstrom} 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 {angstrom}, indicating strain relaxation which is accompanied by increased misorientation. By controlling the structure of ultrathin Al{sub 2}O{sub 3} films, metal-oxide-semiconductor capacitors with Al{sub 2}O{sub 3} gate dielectrics on 4H-SiC were found to have a very low leakage current density, suggesting suitability of Al{sub 2}O{sub 3} for SiC device integration.