The Effect of Anisotropy on Resonant Tunnelling Spin Polarization in Type-II Heterostructures

Abstract

The effect of anisotropy on resonant tunnelling spin polarization in type-II semiconductor heterostructures is investigated within the envelope function approximation. Calculations are performed using an 8 x 8 kp matrix Hamiltonian which includes the interband coupling between electrons and holes as well as the non-parabolicity and anisotropy of the energy band structure. The polarization is due to constant applied magnetic field directed along the growth directions of samples which are grown at arbitrary angles with respect to the c[001] axes. Using spin-dependent boundary conditions and the transfer matrix method, an analytical expression for the spin polarization is obtained. Numerical calculations of the polarization reveal that it is highly sensitive to the anisotropy parameters of the model. Even under relatively weak magnetic fields polarizations of up to 75% are predicted.