We demonstrate room-temperature, single-mode, continuous-wave operation of a lambdasimilar or equal to5.4 mum quantum-cascade laser up to the temperature of 30 degreesC. Processing is done using standard lithography in a ridge waveguide mounted junction-up. The active region is based on a bound-to-continuum transition. The high performances were achieved with a low active region doping and a thick electroplated gold deposition, resulting in a characteristic temperature of T-0=155 K in continuous-wave with a threshold current density of j(th)=2.05 kA/cm(2) at 300 K. (C) 2005 American Institute of Physics.