Good quality In0.~2Ga0.88As0.34P0.8~ layers lattice matched to GaAs0.6~P0.~ epitaxial substrates were grown by liquid-phase epitaxy. The electrical and optical properties of the un-, Te-, and Zn-doped In0.~2Ga0.~As0.~P0.~6 layers are described in detail. By selection of the optimum growth condition, we can obtain the undoped layer with an electron concentration of 2 • 10 ~6 cm -~. Room-temperature carrier concentrations ranging from-1.8 • 101~ to 3.4 • 10 ~ cm -~ for n-type and from 1.6 • 10 ~ to 2.8 • 10 ~8 cm -~ for p-type dopants are obtained. The relative intensity of 300 K photoluminescence (PL) spectra presents the maximum values at 6 • 10~Tand 1 • 10 ~ cm -~ for electron and hole concentrations, respectively. The acceptor ionization energy for Zn also is described from the 50 K PL spectra. The five major emission peaks observed from the temperature dependence of PL spectra for the Zn-doped InGaAsP layer are identified clearly. Finally, the p-n homostructure orange LEDs were fabricated to exhibit the emission peak wavelength and the full width at half maximum of electroluminescence of ca. 619 nm and 53 meV, respectively.