AVS 50th International Symposium
    Semiconductors Tuesday Sessions
       Session SC-TuA

Paper SC-TuA7
Real-time Diagnostics of OMCVD Epitaxy with an Integrated Rotating-compensator/Rotating-sample Polarimeter

Tuesday, November 4, 2003, 4:00 pm, Room 321/322

Session: Compound Semiconductor Growth and Processing
Presenter: M. Asar, North Carolina State University
Authors: K.F. Flock, North Carolina State University
S.J. Kim, North Carolina State University
M. Asar, North Carolina State University
D.E. Aspnes, North Carolina State University
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We obtain new insights on III-V epitaxy and heteroepitaxy with a rotating-compensator/rotating-sample ellipsometer/polarimeter for diagnostics and control of organometallic chemical vapor deposition (OMCVD). The system obtains up to 5 1024-pixel spectra per second from 230 to 840 nm, allowing the p- and s-polarized reflectances and the complex reflectance ratio to be determined from the dc, 2@omega@t, and 4@omega@t components of the transmitted intensity. In addition the optical anisotropy follows from the 10@omega@t component, and alignment parameters from the @omega@t and 3@omega@t components, providing the maximum amount of sample information obtainable from optical data over the available spectral range. Rotating-compensator operation eliminates the serious shortcoming of older, rotating-analyzer and -polarizere designs associated with the loss of phase information when the phases of the complex reflectance ratios are near 0 or 180 degrees. The anisotropy data returns surface-chemical information through their spectral dependences. We relate these non-normal-incidence anisotropy spectra to RDS data obtained at normal incidence by numerical analysis of the system transfer function. This combination of capabilities allows OMCVD growth processes to be studied in greater detail, especially when combined with a recently developed algorithm for simultaneously determining the thickness and dielectric function of films in the Å thickness range. For example we follow the growth of nm thick layers of Ga on (001)GaAs substrates, and track the connection between surface reconstruction and film growth. The relatively short data-acquisition time also allows us to follow growth under highly nonequilibrium "burst" conditions, which appear to be necessary to establish uniform layers of some III-V materials on chemically different substrates.