Large spontaneous spin splitting in gate-controlled two-dimensional electron gases at normal In0.75Ga0.25As/In0.75Al0.25As heterojunctions

Amounts of spontaneous spin splittings were estimated from low-temperature magnetoresistances in two-dimensional electron gases created at In0.75Ga0.2 5As/In0.75Al0.25As heterojunctions under a gate bias. Typical sheet electro n densities and mobilities in the raw wafers were similar to1.0 x 10(12)/cm (2) and 2-5 x 10(5) cm(2)/V s at 1.5 K, respectively. A maximum spin-orbit coupling constant alpha (zero) of similar to 30(x10(-12) eV m) was obtained for the van der Pauw sample. In gated Hall-bar samples, a decrease in the alpha (zero) value with decreasing gate voltage (V-g) was first confirmed i n a normal heterojunction. The main origin for such a large alpha (zero), w hich is a few times larger than any previously reported, was found to be a structure-dependent so-called interface contribution in the Rashba term. (C ) 2001 American Institute of Physics.