GaMnAs samples with various Mn concentrations and different thicknesses, grown by molecular beam epitaxy at low temperature (LT-MBE GaMnAs), are studied in this thesis....[ Read more ]

GaMnAs samples with various Mn concentrations and different thicknesses, grown by molecular beam epitaxy at low temperature (LT-MBE GaMnAs), are studied in this thesis.

Firstly, the carrier concentration of the LT-MBE GaMnAs samples is determined by optical techniques in this thesis, instead of using standard transport techniques, as the latter has a difficulty due to the dominance of the anomalous Hall effect. Most of the experimental results are related to Raman scattering as well as reflectance difference spectroscopy (RDS). The optical determination of the carrier concentration in the LT-MBE GaMnAs thin films has been demonstrated for different thicknesses and different manganese concentrations.

In addition, the Mn concentrations are estimated using the Mn vapor pressure during materials growth and calibrated by X-ray photoemission spectrum (XPS). The crystal structure of the as-grown GaMnAs samples is characterized by high resolution X-ray diffraction (HRXRD) and their Curie temperature is measured by zero-field resistivity of the thin films.

Finally, as the hole concentration p as well as the Mn concentration x are important parameters for GaMnAs since its Curie temperature increases with increase of x and p, their relationship is discussed in the thesis. It is concluded that the experimental results from our samples agree with the prediction of the mean field theory.