Weak localization in back-gated Si/${\mathrm{Si}}_{0.7}$${\mathrm{Ge}}_{0.3}$ quantum-well wires fabricated by reactive ion etching

The electronic properties of Si/${\mathrm{Si}}_{0.7}$${\mathrm{Ge}}_{0.3}$ quantum-well wires fabricated by reactive ion etching are investigated. The width of the nonconducting layer produced by the dry-etch damage and surface depletion is determined by plotting the conductance vs wire width for wires with lithographic widths ranging from 0.10 to 1.0 μm. The combined width of the so-called ‘‘dead layers’’ on each edge of the wire is determined to be as small as 0.13±0.01 μm. Quantum interference effects are studied in wires with lithographic widths of W=0.23 μm. One-dimensional (1D) weak localization is evident in these wires at T=1.3 K in the form of a pronounced negative magnetoresistance for |B|⩽0.3 T. A back-gate contact is used to study the electron-transport properties in the wires, as a function of the electron sheet concentration, ${\mathit{n}}_{\mathit{s}}$. The data have been fitted to the 1D theory of weak localization, and indicate that the inelastic mean free path ${\mathit{L}}_{\mathrm{\phi }}$ increases from 0.2 to 1.2 μm as ${\mathit{n}}_{\mathit{s}}$ is increased from 4.2×${10}^{11}$ to 5.9×${10}^{11}$ ${\mathrm{cm}}^{\mathrm{-}2}$ at T=1.3 K. © 1996 The American Physical Society.