We present a detailed study on Ga_xIn_1-xAs_yP_1-y, lattice-matched to GaAs, grown by gas-source molecular beam epitaxy (GSMBE). First, we investigate the growth mechanism of GSMBE growth of Ga_xIn_1-xAs_yP_1-y/GaAs. Secondly, characterizations, such as X-ray diffractions, Hall measurements, and room temperature and low temperature photoluminescences, have been carried out for the GSMBE-grown Ga_xIn_1-xAs_yP_1-y/GaAs over the entire composition range. Finally, high performance Al-free Ga(In)As(P)/GaInAsP/GaInP compressive-, zero- and tensile-strained, and strain-compensated quantum well lasers, emitting at 0.78 ≤ λ ≤ 1.1 μm, have been fabricated. Also low leakage current GaInAsP/GaAs heterojunction diodes are prepared. The results demonstrate that GSMBE is capable to grow high quality GaInAsP lattice-matched to GaAs over the entire composition range, and that GSMBE-grown GaInAsP is a promising material for optoelectronic applications and a possible substitute for AlGaAs for some special applications.