Localization and Spin-orbit coupling in InGaAs digital alloy quantum wells

InGaAs two dimensional electron gases (2DEGs) have high spin-orbit coupling, making them potentially useful for spintronics [1] and topological quantum computing applications [2,3]. Digital alloying, or growing the ternary as a superlattice, is an alternative to growing ternary III-V as a random alloy. However, the effect of digital alloying on the properties of quantum wells such as the spin-orbit coupling and charge carrier localization is not well understood. Digital alloy quantum wells can potentially enhance the Rashba spin-orbit coupling by forming asymmetric interfaces. Here, we use molecular beam epitaxy and magnetotransport to study the role of random and digital alloying of the spin-orbit coupling and localization of InGaAs quantum wells.

 

From low temperature magnetotransport, the spin-orbit coupling of the quantum wells is studied from the weak localization in the magnetotransport data at different electron densities. The localization of the electrons is further studied in the metal insulator transition of the quantum wells at low carrier densities. We observe enhanced localization in the low carrier density regime in the digital alloy quantum wells. We discuss the role of interfaces on the differences in the spin-orbit coupling and electron localization observed in the random and digital alloy quantum wells.

 

[1] S. Datta et al,. Appl. Phys. Lett. 56, 665 (1990)

[2] R.M. Lutchyn et al., Phys. Rev. Lett. 105, 077001 (2010)

[3] Y. Oreg et al., Phys. Rev. Lett. 105, 177002 (2010)