InGaAs quantum-wire field-effect transistors (QWR-FETs) have been fabricated on (311)A InP V-groove substrates by hydrogen-assisted molecular beam epitaxy. Enhanced negative differential resistance (NDR) effects with a peak to valley ratio (PVR) as high as 13.3 have been observed at an onset voltage of 0.17 V in the QWR-FETs at 24 K. The NDR-FET is a velocity modulation transistor based on a subband transfer of electrons from the high mobility fundamental level to the low mobility higher subband levels. The NDR effects were observed up to 260 K as the In content was increased to 0.8. A unique feature of the QWR-FET is that NDR effects are controllable with the gate bias in a three-terminal configuration, and they are favorable for high speed and high frequency modules with reduced circuit complexity.