Electron-spin polarization in symmetric type-II quantum wells from bulk inversion asymmetry

Abstract

The effect of the bulk inversion asymmetry on electron-spin polarization by resonant tunneling in symmetric, nonmagnetic, type-II semiconductor quantum wells is investigated within the envelope function approximation. A $14\ifmmode\times\else\texttimes\fi{}14\mathbf{k}\ensuremath{\cdot}\mathbf{p}$ matrix Hamiltonian is used which includes the nonparabolicity and spin-split nature of the energy-band structure. Spin-dependent boundary conditions are derived and the transfer-matrix method is applied to obtain analytical expressions for the electron-spin polarization in single- and double-quantum wells. Numerical calculations of the polarization are performed for quantum well systems made from InAs and GaSb. It is shown that the inversion asymmetry of the bulk materials can produce electron-spin polarizations of up to $90%$ for oblique tunneling.