Contactless electroreflectance approach to study the Fermi level position in GaInNAs/GaAs quantum wells.

A fruitful approach to study the Fermi level position in GaInNAs/GaAs quantum wells (QWs) has been proposed in this paper. This approach utilizes contactless electroreflectance (CER) spectroscopy and a very simple design of semiconductor structures. The idea of this design is to insert a GaInNAs quantum well (QW) into a region of undoped GaAs layer grown on n-type GaAs substrate. The possible pinning of the Fermi level in the GaInNAs QW region modifies band bending in this system. In CER spectra both QW transitions and GaAs-related Franz-Keldysh oscillations (FKOs) are clearly observed. The analysis of QW transitions allows one to determine the band gap discontinuity at GaInNAs/GaAs interface whereas the analysis of FKOs allows one to determine the built-in electric field in the GaAs cap layer, and, finally, one is able to find the Fermi level pinning in GaInNAs QW region. [ABSTRACT FROM AUTHOR]