Anti-Weak-Localization Study of Rashba Spin-Splitting Energy as a Function of Well Asymmetry in InAlAs/InGaAs/InAlAs Qua
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Anti-Weak-Localization Study of Rashba Spin-Splitting Energy as a Function of Well Asymmetry in InAlAs/InGaAs/InAlAs Quantum Wells Takaaki Koga, Junsaku Nitta, Tatsushi Akazaki and Hideaki Takayanagi NTT Basic Research Laboratories, NTT Corporation, Morinosato-Wakamiya 3-1, Atsugi, Kanagawa, 243-0198, Japan ABSTRACT We have investigated the values of the Rashba spin-orbit coupling constant α in In0.52Al0.48As/In0.53Ga0.47As/In0.52Al0.48As quantum wells using an anti-weak-localization (AWL) analysis as a function of quantum well asymmetry. We have found that the deduced α values have strong correlations with the structural inversion asymmetry of the pertinent quantum wells as predicted theoretically. This fact suggests that the AWL analysis provides a reliable way to deduce α values experimentally for designing future spintronics devices. INTRODUCTION There has been growing interest in the field of “spintronics” [1], which involves the exploration of the extra degrees of freedom provided by electron spin, in addition to those due to electron charges, with a view to realizing new functionalities in the future electronics devices [2-5]. One key to realizing such spin devices is the utilization of the spin-orbit (S.O.) interaction caused by the structural inversion asymmetry (Rashba effect) in quantum wells (QW) [6], which leads to a zero-field spin-splitting energy ∆0 at Fermi level and can be artificially controlled by controlling the applied gate voltages [7-10] and/or by specific design of the heterostructure [11]. Although whether or not the Rashba effect really exists in a real experimental system is still a controversial issue [12-16], we have recently shown that the anti-weak-localization (AWL) measurement provides a promising way to deduce the values of Rashba S.O. coupling constant α of a two-dimensional electron gas (2DEG) [17-19]. In the present work, we have employed the AWL approach to study the α values of In0.52Al0.48As/In0.53Ga0.47As/In0.52Al0.48As QWs quantitatively as a function of the degree of their structural inversion asymmetry (SIA). We first control the SIA of the pertinent QWs by controlling the impurity densities in the carrier supplying layers located near the QWs [17]. Second, we will show our results when the SIA of the QWs was controlled remotely by varying the pinning position of the chemical potential at the substrate/buffer layer interface. EXPERIMENTAL DETAILS In0.52Al0.48As/In0.53Ga0.47As/In0.52Al0.48As QW samples used in the present study were grown by the MOCVD method. The layer structure of these samples is sketched in Fig.1(a). The whole structure was grown on a (001) oriented semi-insulating InP substrate, where the layer structure consists of (1) a non-doped In0.52Al0.48As buffer layer (either 200 or 100 nm thick) that is grown on top of the substrates, (2) a 6 nm thick carrier supplying (C.S.) layer (In0.52Al0.48As) whose impurity density is N1 cm-3, (3) a 6 nm thick non-doped spacer layer (In0.52Al0.48As), (4) a 10nm thick In0.53Ga0.47As quantum well layer (non-doped), (5) an
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