Control of spin relaxation and spin precession in diffusive 2DEG channels

In this work, we present spintronic devices which allow efficient electrical spin injection and detection into a semiconductor heterostructure with a 2DEG channel. Introducing an enhanced device geometry allows realizing narrow transport channels with a width down to 400nm, thus approaching the 1-dimensional spin transport regime. This considerable spatial confinement gives rise to a significant suppression of spin relaxation, for instance, but also allows identifying spin orbit coupling (SOC) related signatures in non-local spin transport measurements. One of the major findings presented in this thesis is the demonstration of the gate tunability of these SOC related spin signal characteristics. Thus, it is possible to extract gate voltage dependent non-local spin signal oscillations, similar to the expected signal modulation in a spin field effect transistor (spinFET) device. Contrary to the spinFET proposal by S. Datta and B. Das [1], however, spin transport is not purely ballistic in the investigated devices, instead it takes place in an intermediate regime between ballistic and diffusive transport. This is a considerable relaxation of the prerequisites required for the realization of a spinFET device, in particular allowing larger device dimensions, for instance, which significantly facilitates investigations of the fundamental physical properties. [1] S. Datta and B. Das, “Electronic analog of the electro-optic modulator”, Applied Physics Letters 56, 665–667 (1990)