Contactless electroreflectance studies of the band filling effect in image

Contactless electroreflectance (CER) method was used to study the properties of Ga1-xMnxAs samples with x=0.014–0.068. From superconducting quantum interference device (SQUID) measurement, the ferromagnetic transition temperature was found to range from 50 to 100 K for these samples. In the CER experiment, in addition to the features commonly observed for GaAs, above band gap feature could be observed at low temperature for some of the samples. The appearance of the above band gap feature is interpreted as due to the band filling effect of holes in the valence band of Ga1-xMnxAs layer. The large amount of free holes raises the Fermi level of the Ga1-xMnxAs above the band edge of the valence band and increases the effective bandgap observed in the CER measurement. The Fermi level obtained from the measurement is around 30 meV which corresponds to a free hole concentration of around View the MathML source. The results indicate that the Fermi level of metallic Ga1-xMnxAs resides in the valence band and is an ordinary metal.