Observation and analysis of epitaxial growth with reflectance-difference spectroscopy

Reflectance-difference (RD) (-anisotropy) spectroscopy has developed into an established diagnostic tool for semiconductor epitaxy. Major advantages include the simplicity of the approach and the capability of performing measurements in real time during growth. Studies to date have emphasized understanding the origin of RD spectra, relating them to electronic and atomic structure of growth surfaces, and using them to obtain information about fundamental mechanisms of epitaxy. The observation of RD oscillations during organometallic chemical vapor deposition, oscillations that are analogous to those seen in reflection high energy electron diffraction intensities during molecular beam epitaxy, is providing new opportunities for growth control. Using (001) GaAs as an example, principles, representative results, and current critical issues are discussed.