Electrical Spin Injection into InAs Wetting Layer

InAs is an attractive material for optoelectronic and high-speed transistor devices due to its small bandgap and high electron mobility. Owing to its large Rashba spin-orbit coupling, the 2DEG formed in InAs-based heterostructures has also been proposed for spin transport within a spin FET$^{1}$. Here we demonstrate efficient spin injection from Fe into a thin ($\sim $3ML) InAs wetting layer (WL) that forms on GaAs before the formation of QDs. Cross sectional TEM shows that the WL is continuous laterally over many microns, and transport measurements reveal 2DEG-like behavior. The WL electroluminescence is readily distinguished from that of the QDs, and dominates emission at higher biases over a wide temperature range up to RT. We measure an optical circular polarization of 26{\%} at 5K due to the injection of spin-polarized electrons from a reverse-biased Fe Schottky contact, which corresponds to an electron spin polarization $>$50{\%} after lifetime corrections, demonstrating that even this remarkably thin layer supports high spin polarization. This polarization stayed relatively constant up to 60K, and decreased to $\sim $6{\%} at RT, consistent with D'yakonov-Perel spin relaxation mechanism. Supported by ONR, NRL core funds, and NSF. $^{1}$ S. Datta and B. Das, Appl. Phys. Lett. \textbf{56}, 665 (1990).