Growth of hexagonal GaN thin films on Si(111) with cubic SiC buffer layers

The growth of GaN films on silicon or sapphire substrates has not been straightforward due to their large mismatch (>13%). SIC is structurally the closest material to GaN (especially cubic form) and has a small lattice mismatch (3.5%) between SiC and GaN, and therefore can be useful as the substrate for GaN. Single-crystal wafers of cubic SiC and GaN, however, are hard to obtain and have not been produced commercially yet. Therefore, a thin layer of cubic SiC on substrates such as Si and oxide single crystals might solve this problem and will be one of a suitable buffer layers for the cubic GaN film growth. Epitaxial cubic SiC buffer layers were grown on either carbonized or uncarbonized Si(1 1 1) substrates as low as temperature of 830 degrees C using a supersonic molecular jet of t-butyldimethylsilane, (CH3)(3)CSiH(CH3)(2), and the polycrystalline hexagonal GaN thin films were subsequently deposited on them at 600 degrees C using a MOMBE system. The buffer layers and the GaN films were characterized by AES, XRD, FTIR, ellipsometry, and X-ray phi(phi)-scan measurements. The growth temperature of t-butyldimethylsilane was much lower than conventional CVD growth temperatures and this is the first report to obtain epitaxial cubic SIC films on Si from t-butyldimethylsilane and new attempt to grow h-GaN thin films on cubic SIC buffer layers. (C) 1998 Published by Elsevier Science B.V. All rights reserved.