Spin-Dependent Tunneling In III-V Semiconductors Soline Richard 1 , Henri-Jean Drouhin 2 , Guy Fishman 1 , Nicolas Rougemaille 2 1 Institut d'Electronique Fondamentale, UMR 8622 CNRS, Université Paris Sud, 91405 Orsay Cedex, France 2 Laboratoire de Physique de la Matière Condensée, UMR 7643-CNRS, Ecole Polytechnique, 91128 Palaiseau Cedex, France. Abstract. We calculate evanescent waves in GaAs-like III-V semiconductors throughout the forbidden band gap taking into account both the absence of inversion center and the spin-orbit coupling. We find that the evanescent energy bands are spin-split and that the evanescent wave functions only exist in limited energy and wave-vector domains. Such tunnel barriers can be used as solid-state spin injectors. INTRODUCTION Evanescent states in semiconductors have been studied for a long time. For instance Chang [1] considered semiconductors oriented in the [100], [111] and [110] directions, with inversion center (O h group) or without inversion center (T d group), but without taking into account the spin-orbit coupling. Chang and Schulman [2] performed a detailed calculation of the band structure of silicon, which belongs to the O h group. Schuurmans and t'Hooft [3] studied semiconductors belonging to the T d group but explicitly discarded terms which lead to odd k terms so that practically they studied GaAs and AlAs as if they were belonging to the O h group. Briefly speaking, calculations about evanescent waves taking into account both the T d group symmetry and the spin-orbit coupling have not been carried out. Here we calculate the evanescent band structure in the fundamental gap of GaAs-like III-V semiconductors including both the spin-orbit coupling and the lack of inversion symmetry, within a 30×30 k.p Hamiltonian framework (H 30 ). These properties enable the design of original solid state spin injectors. CALCULATION IN H 30 FORMALISM We have calculated the H 30 eigenvalues for a GaAs semiconducting barrier. The energy origin is set at the top of the valence band. The most important is that our parameters yield the γ value of 24 eV.ų,[4] a parameter which characterizes the strength of the D’yakonov-Perel’ field, responsible for the real conduction band spin splitting .The result of the calculation in the k = [iK, Q, 0] direction, where K and Q are real, is plotted in Fig. 1 for Q/K = 3/7. These directions are indexed by the angle θ they form with respect to the imaginary K axis (tan θ = Q / K) -1 -0.5 0 0.5 1 1.5 2 2.5 -0.2 -0.1 0 0.1 0.2 ||k|| (unit of 2 π /a) Energy (eV) [iK,Q, 0] [K,Q, 0] FIGURE 1. Evanescent states connecting the spin-split conduction band to the upper valence bands throughout the fundamental gap. Q/K = 3/7 and a is the cubic lattice constant. 1345 Downloaded 26 Aug 2005 to 146.246.244.6. Redistribution subject to AIP license or copyright, see http://proceedings.aip.org/proceedings/cpcr.jsp CP772, Physics of Semiconductors: 27 th International Conference on the Physics of Semiconductors, edited by José Menéndez and Chris G. Van de Walle © 2005 American Institute of Physics 0-7354-0257-4/05/$22.50