WEAK-LOCALIZATION IN BACK-GATED SI SI0.7GE0.3 QUANTUM-WELL WIRES FABRICATED BY REACTIVE ION ETCHING/

The electronic properties of Si/Si0.7Ge0.3 quantum-well wires fabricat ed by reactive ion etching are investigated. The width of the noncondu cting layer produced by the dry-etch damage and surface depletion is d etermined by plotting the conductance vs wire width for wires with lit hographic widths ranging from 0.10 to 1.0 mu m. The combined width of the so-called ''dead layers'' on each edge of the wire is determined t o be as small as 0.13 +/- 0.01 mu m. Quantum interference effects are studied in wires with lithographic widths of W = 0.23 mu m. One-dimens ional (1D) weak localization is evident in these wires at T = 1.3 K in the form of a pronounced negative magnetoresistance for \B\less than or equal to 0.3 T. A back-gate contact is used to study the electron-t ransport properties in the wires, as a function of the electron sheet concentration, n(s). The data have been fitted to the 1D theory of wea k localization, and indicate that the inelastic mean free path L(phi), increases from 0.2 to 1.2 mu m as n(s) is increased from 4.2 x 10(11) to 5.9 x 10(11) cm(-2) at T = 1.3 K.