  Time resolved spin-polarized electron photoemission spectra are investigated
as a function of excitation pulse energy for the heterostructures with a single
strained layer and with a strained-well superlattice. At an average current
exceeding 10 nA the emission pulse profiles are modified by the space charge
pulse expansion during the electron transport to detector. The pulse expansion
enables the separation of electrons that have spent minimum time in the sample.
For the superlattice structure these electrons showed maximum polarization
above 90 %. Variation in the pulse profiles for the two structures is
interpreted as resulting from the difference in the effective NEA values.
