Datta-Das transistor: Significance of channel direction, size-dependence of source contacts, and boundary effects

TL;DR

This paper investigates how channel direction, contact size, and boundary effects influence the performance of the Datta-Das transistor, highlighting the robustness of the [110] channel direction under various conditions.

Contribution

It generalizes spin injection analysis to finite-sized systems and identifies the [110] channel as optimal for device stability and performance.

Findings

Finite-size injection effects are moderate.

Boundary reflections can cause unexpected changes.

Strong spin-orbit coupling reduces boundary effects.

Abstract

We analyze the spin expectation values for injected spin-polarized electrons (spin vectors) in a [001]-grown Rashba-Dresselhaus two-dimensional electron gas (2DEG). We generalize the calculation for point spin injection in semi-infinite 2DEGs to finite-size spin injection in bounded 2DEGs. Using the obtained spin vector formula, significance of the channel direction for the Datta-Das transistor is illustrated. Numerical results indicate that the influence due to the finite-size injection is moderate, while the channel boundary reflection may bring unexpected changes. Both effects are concluded to decrease when the spin-orbit coupling strength is strong. Hence [110] is a robust channel direction and is therefore the best candidate for the design of the Datta-Das transistor.