Spin Polarized Electron Transport and Emission from Strained Semiconductor Heterostructures

High resolution energy distribution curves (EDC) and a polarization versus energy distribution curves (PEDC) of the electrons, photoemitted from strained GaAs/GaAsP layers are experimentally studied. In the vicinity of the photoexcitation threshold the polarization does not vary across the energy distribution, which means that no depolarization occurs during energy relaxation in the band bending region (BBR). The electron energy distribution is interpreted in terms of the electron energy relaxation in the band tail states of quantum well formed by the BBR. Polarized electron emission from a series of new strained short-period AlInGaAs/AlGaAs superlattices (SL) is investigated as well. The In layer content was chosen to give minimal conductionband offset with large strain splitting of the V-band. Simultaneous changing of Al content in both SL layers provides variation of the structure band gap. We demonstrate as well that tuning of the SL to the excitation energy can be achieved without loss of the electron polarization. The polarization of up to 84% was measured at room temperature.