The concept, the present status, key issues and future prospects of a novel hexagonal binary decision diagram (BDD) quantum circuit approach for III-V quantum large-scale integrated circuits (QLSIs) are presented and discussed. In this approach, the BDD logic circuits are implemented on III-V semiconductor-based hexagonal nanowire networks controlled by nanoscale Schottky gates. The hexagonal BDD QLSIs can operate at delay-power products near the quantum limit in the quantum regime as well as in the many-electron classical regime. To demonstrate the feasibility of the present approach, GaAs Schottky wrap gate (WPG)-based single-electron BDD node devices and their integrated circuits were fabricated and their proper operations were confirmed. Selectively grown InGaAs sub-10 nm quantum wires and their hexagonal networks have been investigated to form high-density hexagonal BDD QLSIs operating in the quantum regime at room temperature. (C) 2002 Elsevier Science B.V. All rights reserved.