SPIN-SPLIT SUBBANDS AND MAGNETO-OSCILLATIONS IN III-V ASYMMETRIC HETEROSTRUCTURES

A quantum-mechanical study of the magneto-oscillations in asymmetric heterostructures is presented with the aim of clarifying the origin and the effects of the spin-orbit spin splitting in the conduction subband, The magnetization of the two-dimensional electron gas at the interface of modulation-doped III-V semiconductor heterojunctions is calculated as a function of applied magnetic field and carrier concentration, taking into account both spin-orbit (zero-field) spin-splitting contributions: one due to the k(3) bulk term and one due to the lack of specular symmetry sigma(k) along the growth direction. Regular beating patterns in the amplitude of the oscillations are shown to originate from the latter term. The k(3) term introduces a k-space anisotropy in the zero-held spin splitting. This leads to anomalous beating patterns, related to the occurrence of a magnetic breakdown at special points of the Fermi surface with a small spin splitting. Experimental evidence of regular beating patterns has been found in InAs-based heterostructures. The possibility of observing anomalous beating patterns in GaSb heterojunctions is discussed.