We report the room‐temperature pulsed operation of GaAs/(Al,Ga)As double heterojunction laser structures grown directly on (100)Si. Current thresholds of as low as 170 mA in 10‐&mgr;m‐wide stripe lasers have been achieved at 280 K. Power output as high as 44 mW per facet was also obtained. Assuming no current spreading, the corresponding current threshold density is 6.9 kA/cm2. Slope efficiencies andT0values of 0.18 W/A and 165 K, respectively, have also been obtained. These results are directly attributable to the reduction of dislocations by choosing growth conditions and step density on the surface.