| AVS 61st International Symposium & Exhibition | |
| Surface Science | Thursday Sessions |
| Session SS+AS+NS-ThA |
| Session: | Semiconductor Surfaces and Interfaces 1 |
| Presenter: | Jacek Kolodziej, Jagiellonian University, Poland |
| Authors: | J. Kolodziej, Jagiellonian University, Poland N. Tomaszewska, Jagiellonian University, Poland P. Ciochon, Jagiellonian University, Poland |
| Correspondent: | Click to Email |
Angle-resolved photoelectron spectroscopy (ARPES) is used to study electronic bands at the n-type InAs(001) surfaces, having several different reconstructions. Indium-rich (8x2)/(4x2)and arsenic-rich c(2x8)/(2x4) surfaces as well as sulphur passivated (2x1) surface are prepared and investigated. Measured electronic bands are identified by analysis of their symmetries in the k-space.
In InAs crystal bulk the conduction band minimum (CBM) is located very close to the Fermi level (FL). Downward band bending, typical for the studied surfaces, causes formation of two dimensional electron gas, confined in a subsurface well, also known as the electron accumulation layer. This is indicated by characteristic quantized subband states visible in the ARPES spectra.
It is shown that the band bending magnitude and the quantization (of the accumulated electron energies associated with the coordinate normal to the surface) depend on the surface reconstruction as well as on the crystal doping. In most cases the electron accumulation bands are found at the Fermi level and close to the Γ1x1 symmetry point in the center of the surface Brillouin zone. The most clear picture is observed for the sulphur passivated (2x1) surface, where three distinct subbands with minima at E1=-0,276eV, E2=-0,096eV and E3=-0,039eV with reference to Fermi level are found. Unexpectedly, for the indium rich surface, occupied conduction states are found also at Γ4x2 symmetry points indicating that, for this case, surface resonances mix with the electron accumulation states.
It is also shown that the observed surface bands are sensitive to surface treatment. Two surface preparation techniques have been used: cycles of ion beam annealing (IBA) and ex situ wet chemical treatment (WCT). Although low electron energy diffraction (LEED) indicates no increased disorder on the IBA surfaces they yield considerably worse electronic band images. This is most likely due to scattering of photoelectrons on the electrically active antisite defects.
We acknowledge financial support by Polish NCN (contract 2011/03/B/ST3/02070). The research was carried out with the equipment purchased thanks to European Regional Development Fund in the framework of the Polish Innovation Economy Operational Program (contract no. POIG.02.01.00-12-023/08).