Search

Spin–orbit interaction effects are of great interest, primarily for the ability to modulate spin transport in a semiconductor channel for device applications. In particular, the Rashba spin–orbit (S–O) interaction allows for a tuneable spin modulation response dependent on the applied electric field, which can be achieved using standard semiconductor gate technology. We present evidence of the Rashba S–O interaction in two modulation doped germanium (Ge) quantum well (QW) heterostructures with different layer structures, and consequently different band structures and internal electric fields across the QW region. We show that two complementary low temperature magnetotransport analyses can be used to identify and quantify the Rashba S–O parameter in these materials, although quantification is limited in one case due to significant parallel conduction. We highlight that both techniques (Weak Antilocalisation and Shubnikov de-Haas oscillations) should be used when analysing a new material system as other conduction and magnetoresistive effects can obscure evidence of the Rashba S–O interaction in one or both of these regimes. [ABSTRACT FROM AUTHOR]

We report magnetotransport measurements of a SiGe heterostructure containing a 20 nm p-Ge quantum well with a mobility of 800 000 cm² V−1 s−1. By dry etching arrays of wires with widths between 1.0 μm and 3.0 μm, we were able to measure the lateral depletion thickness, built-in potential, and the phase coherence length of the quantum well. Fourier analysis does not show any Rashba related spin-splitting despite clearly defined Shubnikov-de Haas oscillations being observed up to a filling factor of ν = 22. Exchange-enhanced spin-splitting is observed for filling factors below ν = 9. An analysis of boundary scattering effects indicates lateral depletion of the hole gas by 0.5 ± 0.1 μm from the etched germanium surface. The built-in potential is found to be 0.25 ± 0.04 V, presenting an energy barrier for lateral transport greater than the hole confinement energy. A large phase coherence length of 3.5 ± 0.5 μm is obtained in these wires at 1.7 K. [ABSTRACT FROM AUTHOR]

We report the observation, through Shubnikov-de Haas oscillations in the magnetoresistance, of spin splitting caused by the Rashba spin-orbit interaction in a strained Ge quantum well epitaxially grown on a standard Si(001) substrate. The Shubnikov-de Haas oscillations display a beating pattern due to the spin split Landau levels. The spin-orbit parameter and Rashba spin-splitting energy are found to be 1.0 x 10-28 eVm³ and 1.4meV, respectively. This energy is comparable to 2D electron gases in III-V semiconductors, but substantially larger than in Si, and illustrates the suitability of Ge for modulated hole spin transport devices. [ABSTRACT FROM AUTHOR]