V-grooved InGaAs/InAlAs quantum-wire field-effect transistors are realized by selective molecular-beam epitaxy and their transport characteristics are studied. The QWR structures are formed using a combination of atomic hydrogen and a dimer arsenic source. An analysis of the depopulation of one-dimensional sub-bands in these structures reveals little evidence for sidewall depletion. Sub-band splittings as large as 6.6 meV are obtained in the wires, indicating their excellent one-dimensional transport properties. (C) 2003 Elsevier Science B.V. All rights reserved.