The room‐temperature operations of an InGaAsP double‐heterostructure (DH) laser emitting at 1.55 &mgr;m on a Si substrate is reported. A pulsed threshold current as low as 46 mA has been measured for a ridge waveguide laser with a 4 &mgr;m strip width and a 200 &mgr;m cavity length. This successful laser operation is due to the high crystalline quality of the DH structure with full width at half maximum of x‐ray rocking curves as low as 110 arcsec grown on a Si substrate by the organometallic vapor phase epitaxy/vapor mixing epitaxy hybrid method. A correlation between the optical property of an InGaAsP DH and its crystalline quality is also discussed.