Low - temperature (LT) molecular beam epitaxy-grown (MBE) GaAs have found many applications in ultrafast, integrated optoelectronic photoswitces and photodetectors. Such layers of GaAs grown by MBE at LT conditions under the arsenic rich flux exibit unique properties, such as ultrashort carrier lifetimes and high resistivity after annealing.
The object of this study - LT-MBE grown GaAs (100) at one temperature and at different As flux conditions by means of angle-resolved photoemission spectroscopy.
The experiment was performed on the toroidal grating monochromator beamline (BL 41) at the MAX I storage ring. A dedicated MBE system is connected to the electron spectrometer, allowing the between the units under ultrahigh vacuum conditions. The valence band spectra for samples prepared at different As flux conditions show very similar features. The peak related with interband transition shifts toward low binding energies, when As flux increase. That can be relate with the change of lattice constant in the LT-GaAs due to increasing of the density of As_Ga antisites with increasing As flux. To identify surface and bulk contribution the Ga 3d and As 3d corel level spectra were taken at different photon energies and take off angles. In Ga 3d spectra appear a new component in compare with HT-GaAs dependents on As flux ratio and is bulk derived. This component origin is bonded with high density of As_Ga antisite point defects in LT-GaAs [1].

Acknowledgment: This work was supported by the European Community-Access to Research Infrastructure of the Improving Human Potential Programme.

[1]. H. Asklund, L. Ilver, J. Kanski, J. Sadowski, M. Karlsteen, Phys. Rev. B 65, 115335 (2002).