Pseudomorphic trench-type InGaAs/InAlAs quantum-wire field-effect transistors (QWR-FETs) are realized on (311)A InP V-groove substrates by selective molecular beam epitaxy. Negative differential resistance (NDR) spectra are clearly observed in the 50-240 K temperature range for the In0.7Ga0.3As QWR-FET, and up to 260 K for the In0.8Ga0.2As QWR-FET. These temperature ranges are higher than that of a lattice-matched QWR-FET, and this is thought to be due to the higher electron mobility in the pseudomorphic QWR layer. The NDR temperature range increases as the QWR In content increases and the FET gate length decreases. © 2005 Elsevier B.V. All rights reserved.