Ellipsometric studies of GaAs$_{1-x}$Bi$_{x}$ (0.00 $\le \quad x \quad \le $ 0.13) alloys

A series of GaAs$_{1-x}$Bi$_{x}$ (0.00 $\le \quad x \quad \le $ 0.13) alloy thin films has been grown by molecular beam epitaxy on GaAs(001). Structural properties were characterized by high-resolution x-ray diffraction and cross-sectional transmission electron microscopy. Above-bandgap optical properties were determined by spectroscopic ellipsometry at room temperature. In order to minimize artifacts from surface overlayers in the measured spectra, \textit{in-situ} wet chemical etching procedures were employed. Major optical structures observed are associated with the $E_{1}$, $E_{1}+\Delta _{1}$, $E$', and $E_{2}$ interband-transition critical-points (CPs). An additional broad optical structure was also found at around 2 eV for high Bi-concentration samples ($x \quad \ge $ 0.04). The CP parameters and their composition-dependences were obtained from the spectral analysis done in reciprocal-space. This abstract is subject to government rights.