The confining potential for carriers in planar doped GaAs and the effect of photoexcitation.

Single Be and Si delta-doped layers in GaAs have been investigated by Raman spectroscopy. GaAs/AlsubxGasub1minusxAs heterointerfaces, placed 30 nm from the dopant spike on either side, facilitate optical measurements by the confinement of photogenerated minority carriers. Self-consistent subband calculations have been performed to compute the subband structure of the two-dimensional electron or hole gas which is confined by the space-charge induced potential well at the delta-doping layer. Upon increasing photoexcitation, the increase in density of photocreated electrons in the Be structure is clearly seen in the polarised Raman scattering spectrum by the appearance, and subsequent increase in frequency, of the electron plasmon modes. The electric field at the top GaAs/AlsubxGasub1minusxAs interface is monitored by measuring the strength of electric field induced LO phonon scattering.