Photoluminescence and carrier lifetime data are obtained on low‐dislocation‐density(etch pits ≳ 5 × 103/cm2)n‐type In1−xGaxP (x=0.52) epitaxial layers grown on (100) surfaces of GaAs by means of a constant‐temperature liquid‐phase‐epitaxial (CT‐LPE) process. These crystals are of exceptional quality and readily lase from 77 to 300 °K. The index dispersion relation (n‐&lgr; dn/d&lgr;) is determined from the laser mode spacing &Dgr;&lgr; in the temperature range 77–300 °K and indicates that at higher thresholds laser operation shifts toward donor tail states. By means of optical phase shift measurements the carrier lifetime (77°K) is examined as a function of wavelength from the spontaneous regime to well above laser threshold. The lifetime data indicate that there is a correlation between a dip in the lifetime due to stimulated emission and the region of the spectrum where the first laser modes appear. These data, and similar data onp‐type crystals, indicate that CT‐LPE In1−xGaxP should be very promising for the development of room‐temperature visible spectrum lasers.