Journal of Crystal Growth 218 (2000) 181}190 The e!ect of AlN bu!er layer on GaN grown on (1 1 1)-oriented Si substrates by MOCVD S. Zamir*, B. Meyler, E. Zolotoyabko, J. Salzman Department of Electrical Engineering and Microelectronics Center, Technion - Israel Institute of Technology, Haifa 32000, Israel Department of Material Engineering, Technion - Israel Institute of Technology, Haifa 32000, Israel Received 29 March 2000; accepted 5 June 2000 Communicated by C.R. Abernathy Abstract GaN "lms were grown by metal organic chemical vapor deposition on (1 1 1)Si substrates, using AlN as a bu!er layer. The in#uence of the AlN bu!er layer growth temperature and growth duration on the morphology and preferred orientation of GaN "lms was studied. Drastic enhancement of epitaxial registration was observed with increasing bu!er growth temperature. A sharp transition in the growth mode occurred at 7603C. For that temperature, an optimal bu!er layer growth duration was found. The use of March parameter as a "gure of merit in X-ray di!raction testing of textured GaN "lms is proposed.  2000 Elsevier Science B.V. All rights reserved. PACS: 81.05.Ea; 81.10.Bk; 81.15.Gh Keywords: GaN; AlN bu!er; GaN-on-Si; MOCVD 1. Introduction The di$culties in growing a large size bulk GaN of high structural perfection have motivated inten- sive search of other materials which could be used as suitable substrates for GaN heteroepitaxy. The substrate's choice is dictated by (i) device require- ments (e.g. electrical and thermal conductivity, chemical stability, etc.), (ii) structural properties (crystal structure type, lattice constants, etc.), and (iii) interface properties (nucleation, adhesion, etc.). * Corresponding author. Tel.: #972-4-8293873, #972-4- 8292613; fax: #972-4-8322185. E-mail address: zshai@tx.technion.ac.il (S. Zamir). Silicon is a very promising substrate material for the growth of GaN layers, allowing future integra- tion of well-established Si electronics with GaN- based photonic devices. To date, several groups have succeeded in fabrication of GaN-based devi- ces on Si substrates [1}3]. However, still the growth of GaN-on-Si layers of crystalline quality comparable to that of GaN layers grown on sap- phire or on SiC substrates is a challenging issue. The commonly mentioned problem of large mis- match between relevant lattice parameters of GaN and Si does not seem to be the main limiting fac- tor for successful heteroepitaxy. In fact, it is known that in complicated situations, when additional factors (besides the lattice mismatch) are present, the epitaxial registration does not necessarily 0022-0248/00/$ - see front matter  2000 Elsevier Science B.V. All rights reserved. PII: S 0 0 2 2 - 0 2 4 8 ( 0 0 ) 0 0 5 7 0 - 4