Surface potential effects in the electro-optic probing of the Hall effect in bulk GaAs

The Hall effect in bulk Si-doped GaAs (n=3.4*10-18 cm -3) has been observed using an electro-optic voltage probing(EOVP)technique, which is non-invasive and eliminates the necessity for metallic voltage probes. Essentially the Hall voltage is measured by detecting the induced birefringence created by this transverse voltage. The change in polarization of the probing beam is plotted as a function of the magnetic field which induces the Hall field. A transverse voltage is observed, without the application of a magnetic field. This >>OPEN 'background' voltage is investigated, and we believe it is due to the surface potential differences between the upper and lower surfaces.