Department of Chemical Engineering, Kansas State University, Manhattan, KS ..... L.V. Interrante, C.L. Czekaj, M.L.J. Hackney, G.A. Sigel, P.J. Schields, and G.A. ...
Mater. Res. Soc. Symp. Proc. Vol. 831 © 2005 Materials Research Society
E3.1.1
Sublimation Growth of Aluminum Nitride-Silicon Carbide Alloy Crystals on SiC (0001) Substrates Z. Gu1, J.H. Edgar1, E.A. Payzant2, H.M. Meyer2, L.R. Walker2, A. Sarua3, M. Kuball3 1 Department of Chemical Engineering, Kansas State University, Manhattan, KS 66506, USA 2 High Temperature Materials Laboratory, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6064 3 H.H. Wills Physics Laboratory, University of Bristol, Bristol BS8 1TL, UK ABSTRACT Thick (up to 1 mm) AlN-SiC alloy crystals were grown on off-axis Si-face 6H-SiC (0001) substrates by the sublimation-recondensation method from a mixture of AlN and SiC powders at 1860-1990 °C in a N2 atmosphere. The color of the crystals changed from clear to dark green with increasing growth temperature. Raman spectroscopy and x-ray diffraction (XRD) confirmed an AlN-SiC alloy was formed with the wurtzite structure and good homogeneity. Three broad peaks were detected in the Raman spectra, with one of those related to an AlN-like and another one to a SiC-like mode, both shifted relative to their usual positions in the binary compounds, and the third broad peak with possible contributions from both AlN and SiC. Scanning Auger microanalysis (SAM) and electron probe microanalysis (EPMA) demonstrated the alloy crystals had an approximate composition of (AlN)0.75(SiC)0.25 with a stoichiometric ratio of Al:N and Si:C. The substrate misorientation ensured a two-dimensional growth mode confirmed by scanning electron microscopy (SEM). INTRODUCTION The aluminum nitride-silicon carbide alloy system (AlN)x(SiC)1-x, possessing a wide range of physical and electronic properties with changing composition, is superior to the pure binary components [1]. It is an excellent system for bandgap engineering, as its band gap is changeable from 6.2 eV (2H-AlN) down to 2.9 eV (6H-SiC) [2], or as low as 2.28 eV if cubic 3C-SiC can be stabilized [3]. The band transition changes from indirect (SiC), to direct for AlN-rich (>70 %) material [4]. Both n and p type conductivities have been reported. A (SiC)1-x(AlN)x pn junction was successfully fabricated as well as pn heterojunction between n type 6H-SiC substrate and p type solid solution [5]. When x≤0.40, the (SiC)1-x(AlN)x on n-SiC is typically p-type, while at high x values the material is n-type [6]. The AlN-SiC system retains the best properties of the pure binary compounds: high electron break down field, high saturated electron drift velocity, and high thermal conductivity. It is a potentially highly dopable wide bandgap compound semiconductor because of the easy dopability of SiC [7]. In addition, AlN is promising for polytype stabilization of wurtzite SiC due to its isostructural form and close lattice match (
