  Electron-phase modulation in magnetic and electric fields will be presented
in In_(0.75)Ga_(0.25)As Aharonov-Bohm (AB) rings. The zero Schottky barrier of
this material made it possible to nanofabricate devices with radii down to
below 200 nm without carrier depletion. We shall present a fabrication scheme
based on wet and dry etching that yielded excellent reproducibility, very high
contrast of the oscillations and good electrical gating. The operation of these
structures is compatible with closed-cycle refrigeration and suggests that this
process can yield coherent electronic circuits that do not require cryogenic
liquids. The InGaAs/AlInAs heterostructure was grown by MBE on a GaAs substrate
[1], and in light of the large effective g-factor and the absence of the
Schottky barrier is a material system of interest for the investigation of
spin-related effects [2-4]} and the realization of hybrid
superconductor/semiconductor devices [5].
