This article reviews briefly the recent progress in the In0.5Ga0.5P and In0.5Al0.5P epilayers lattice-matched to GaAs grown by gas source molecular beam epitaxy (GSMBE). It covers the growth conditions, and the structural, electrical, and optical properties. Important research results on the electronic and photonic device applications of these materials grown by GSMBE are also reviewed and discussed. We focus on the InGaP/InGaAs and InAlP/InGaAs pseudomorphic modulation-doped field-effect transistors, InGaP/GaAs and InAlP/GaAs heterojunction bipolar transistors, short wavelength visible laser diodes, and 0.98 mum lasers using In0.5Ga0.5P as the cladding layers. The results clearly demonstrate that high quality In0.5Ga0.5P and In0.5Al0.5P heterostructures prepared by GSMBE are suitable for state-of-the-art device applications.