Figure 1: Description of valley splitting and system explored.
From: Genetic design of enhanced valley splitting towards a spin qubit in silicon
Schematic representation of (a) the (sixfold degenerate) Δ-valley state of bulk Si; (b) splitting between XY-valley and Z-valley by tensile biaxial strain; and (c) splitting of Z-valleys by the abrupt interfaces of the quantum well. Note that the confinement barrier height for the well is the band offset (between Si well and barrier) of Z-valley (b-Valley), higher than the band offset of conduction band minima (b-CBM). The symmetry of Si quantum well of N monolayers alternates from D2d ↔ D2h for N odd ↔ even, respectively. (d) Heterostructure geometry adopted in the present study. A [001]-oriented Si quantum well of thickness d and the surrounding barriers are coherently strained by epitaxial growth over a specified substrate. Both barrier and substrate are composed of Si–Ge-based materials.
