AVS 46th International Symposium
    Electronic Materials and Processing Division Friday Sessions
       Session EM-FrM

Paper EM-FrM8
Migration-Enhanced Epitaxy of CuInSe@sub 2@

Friday, October 29, 1999, 10:40 am, Room 608

Session: In Situ Monitoring and Growth
Presenter: B.J. Stanbery, University of Florida
Authors: B.J. Stanbery, University of Florida
S. Kincal, University of Florida
S. Kim, University of Florida
O.D. Crisalle, University of Florida
T.J. Anderson, University of Florida
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We describe a novel rotating-disc MBE reactor that implements a Migration-Enhanced Epitaxy (MEE) process@footnote 1@ and its application to the growth of Copper Indium Selenide (CIS) on GaAs and ZnTe single-crystal substrates. MEE is a process variant of conventional MBE and one of a general class of Modulated-Flux Deposition (MFD) processes that are based on cyclic alternation between deposition and relaxation steps, and the separation of cationic and anionic species fluxes. All of these measures are intended to achieve long surface diffusion lengths and promote adatom/substrate equilibration. Our reactor is divided by carefully designed shielding into four nominally isolated zones: metals (Cu+In) deposition, cooling, chalcogen (Se,S) deposition and heating. The fixed substrate heater in the latter zone combined with the rotating-disc design results in cyclic heating and cooling of the substrates. The direction of substrate rotation can be reversed, enabling two different growth cycles. The cooling zone includes a source for dosing the substrates with dopants or surfactants. We will present the results of our molecular and thermal flux modeling and discuss their implications for surface growth kinetics in our reactor. We will also present XRD, AFM, Auger, SIMS and PL data characterizing our successful epitaxial growth by MEE of (001)CuInSe@sub 2@ on (001)GaAs and (001)ZnTe. Our data also shows phase segregation of Cu@sub 2-X@Se in copper-rich epilayers and a relative loss of crystal quality in indium-rich epilayers. We will discuss the relevance of these results to our free-energy thermochemical defect model of the Cu-In-Se ternary system. We show that these data provide evidence of a transition from Stranski-Krastonov to Frank-Van de Merwe growth mode when the surface is dosed with small quantities of sodium fluoride during the initial stages of epitaxy on (001)ZnTe, supporting our thesis@footnote 2@ that sodium behaves as a surfactant in this material system. @FootnoteText@ @footnote 1@ Y. Horikoshi, M. Kawashima, and Y. Yamahuchi, Jap. J. Appl. Phys. 25, 1986, p. L868. @footnote 2@ B.J. Stanbery, C.-H. Chang, and T.J. Anderson, 11th International Conference on Ternary and Multinary Compounds, 1997, Inst. of Phys. Conf. Series 152, pp. 915-922.