GROWTH BY MOLECULAR-BEAM EPITAXY AND ELECTRICAL CHARACTERIZATION OF SI-DOPED ZINC BLENDE GAN FILMS DEPOSITED ON BETA-SIC COATED (001) SI SUBSTRATES

We report the electrical characteristics of heavily Si-doped zinc blende GaN epilayers deposited on beta-SiC coated (001) Si substrates. The beta-GaN films were grown by molecular beam epitaxy using a rf plasma discharge, nitrogen free-radical source, and the doping concentration in the films was controlled over the range 1.5 x 10(18)-3.0 X 10(20) cm-3 by suitably adjusting the temperature of a Si effusion cell. We have found that Si incorporation in beta-GaN results in a relatively deep donor level (approximately 62 meV below the conduction band edge at a carrier concentration at room temperature of 10(18) cm-3). Also, we present evidence of simultaneous high mobility conduction band conduction (dominant at high temperatures) and low mobility impurity band conduction (dominant at temperatures <70 K) in heavily doped (n(RT)>10(19) cm-3) material.