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(Color online) VS in an ideal miscut QW: (a) minimal ideal unit cell of a miscut QW consisting of four steps ( for 2° tilt). (b) Band structure of a miscut QW grown on the surface can be obtained by projecting conduction band valleys at onto the QW growth surface Ref. 19. Two degenerate valleys are located at along . (c) Valley-valley interaction at the crossing causes a minigap at Refs. 20 and 21. Lowest valleys are degenerate. Here, . (d) Confinement the in direction causes quadrate of states in two degenerate valleys centered at to interact and split. All band structures in (b)–(d) are calculated with with spin-orbit coupling. Conventional tetrahedral unit cell is used to obtain bulk Si band structures of (b). Lateral extensions of QWs of (c) and (d) are , , and thickness is .
(Color online) (a) Schematic of heterostructure and confining potential along growth direction. (b) Atomic scale representation of a disordered interface. (c) Ideal steps along the  direction in the plane. (d) Schematic of the step disorder along the direction in heterostructures grown on 2° miscut substrates. Flat and disordered steps alternate Ref. 13.
(Color online) (a) VS in a flat QW and SS in flat and miscut QWs. VS increases due to the SiGe alloy disorder. SS remains unchanged by disorders or miscut surfaces. (b) VS in 2° miscut Si QWs in the presence of realistic disorders. Error bars represent standard deviation in VS. VS is enhanced due to step as well as alloy disorder and is on the same order of magnitude as reported in experiments Ref. 9.
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