NOVELTY - A gallium-aluminum-indium-phosphide compound semiconductor is produced by controlling flow rates of zinc and selenium vapors supplied to a region for epitaxial crystal growth to produce a heavily doped gallium-aluminum-indium-phosphide compound semiconductor with zinc serving as a p-type dopant at an atomic ratio of zinc:selenium greater than two in a gallium-aluminum-indium-phosphide crystal.    USE - For the production of GaAlInP compound semiconductor (claimed) used in optoelectronic devices, e.g. tandem solar cells, high brightness visible LEDs, or in visible laser diodes.    ADVANTAGE - The method uses two doping atoms, an n-type (Se) and a p-type (Zn), to increase the p-type conductivity thus greatly enhancing the incorporation of Zn acceptor impurities in AlInP lattice-matched to GaAs compound substrates. It uses the simultaneous doping with both donor (Se) and acceptor (Zn) impurities to enhance solubility of Zn and the doping level in p-type AlInP. By increasing the n-type donor to a sufficient level, the incorporation of the p-type acceptor will increase significantly thus lowering the resistivity and increasing the conductivity of the AlInP crystal.    DETAILED DESCRIPTION - Production of gallium-aluminum-indium-phosphide (GaAlInP) compound semiconductor comprises:    (a) disposing a Ga-arsenide (As) single crystal as a substrate in a metal organic chemical vapor deposition (MOCVD) reactor;    (b) preparing Al, Ga, In vapors by thermally decomposing organometallic compounds of Al, Ga, and In;    (c) preparing zinc (Zn) vapors by thermally decomposing an organometallic Zn compound;    (d) preparing P vapors by thermally decomposing phosphine (PH3) gas;    (e) simultaneously supplying the Al, Ga, In, P, selenium (Se), and Zn vapors to a region for epitaxial crystal growth on the substrate; and    (f) epitaxially growing a GaAlInP crystal doped with Zn and Se on the substrate.    The flow rates of the Zn and Se vapors supplied to the region for epitaxial crystal growth are controlled to produce a heavily doped GaAlInP compound semiconductor with Zn serving as a p-type dopant at an atomic ratio of Zn:Se greater than two in the GaAlInP crystal.