Accession Number : ADA331740

Title :   Defects and Impurities in 4H- and 6H-SiC Homoepitaxial Layers: Identification, Origin, Effect on Properties of Ohmic Contacts and Insulating Layers and Reduction

Descriptive Note : Quarterly technical rept. 1 Jul-30 Sep 97

Corporate Author : NORTH CAROLINA STATE UNIV AT RALEIGH DEPT OF MATERIALS SCIENCE AND ENGINEERING

Personal Author(s) : Davis, R. F. ; Aboelfotoh, M. O. ; Baliga, B. J. ; Nemanich, R. J. ; Benjamin, M. C.

PDF Url : ADA331740

Report Date : SEP 1997

Pagination or Media Count : 40

Abstract : Aluminum nitride (AlN) thin films with very smooth surfaces have been grown by gas-source molecular beam epitaxy on 4H- and 6H-SiC substrates. Streaked reflection high energy electron diffraction patterns and reconstructions of the AlN surfaces indicated smooth films. Atomic force microscopy (AFM) and transmission electron microscopy (TEM) showed root mean square values less than or equal 1 nm and very flat surfaces, respectively. X-ray diffraction showed the films to be highly c-axis oriented and single phase. Major impurities in the AlN films were oxygen and carbon, as revealed by secondary ion mass spectrometry. A correlation has been found between the types and the distributions of the dominant defects, namely, micropipes and screw dislocations using optical microscopy, scanning electron microscopy, AFM, synchrotron white beam x-ray topography, and electron beam induced current (EBIC) studies. A ridge-type structure of the core of the micropipes, related to the growth front flow direction was observed with AFM. Triangular micro inclusions associated with the cubic 3C-SiC polytype (beta-SiC) were detected. EBIC studies revealed various types of electrically active defect regions, related to the beta-SiC phase and randomly distributed within the wafers and across different Shottky diodes. X-ray photoelectron spectroscopy, Auger electron spectroscopy (AES), low energy electron diffraction (LEED), and temperature programmed desorption (TPD) revealed that exposure of 6H-SiC to atomic hydrogen selectively removes Si from the surface and converts the (3x3) surface to a (1x1) surface. Additional etching of this surface was indicated by the reduction in the Si LVV/C KLL ratio in AES from 1.3 to 0.4 following exposure of (3x3) surfaces to a remote rf H plasma.

Descriptors :   *SILICON CARBIDES, *MOLECULAR BEAM EPITAXY, SCANNING ELECTRON MICROSCOPES, ALUMINUM COMPOUNDS, THIN FILMS, X RAY DIFFRACTION, NITRIDES, ELECTRON DIFFRACTION, AUGER ELECTRON SPECTROSCOPY.

Subject Categories : Crystallography
      Atomic and Molecular Physics and Spectroscopy
      Nuclear Physics & Elementary Particle Physics

Distribution Statement : APPROVED FOR PUBLIC RELEASE