Pressure dependence of photoluminescence in ordered Ga0.5In0.5P grown on (001) GaAs by organometallic vapor phase epitaxy

Abstract

Photoluminescence (PL) measurements on Ga0.5In0.5P grown by organometallic vapor phase epitaxy on (001) GaAs substrates at various growth temperatures have been made as a function of pressure up to about 4.5 GPa at 77 K. The PL spectrum shows a markedly sublinear shift to higher energies with pressure up to about 3.8 GPa; this corresponds to a sublinear increase in the E0 direct band gap. The pressure coefficients were obtained through a quadratic fit to the data between atmospheric pressure and 3.5 GPa. The sample grown at the highest temperature shows a significantly smaller linear coefficent than that grown at the lowest temperature. The tendency of saturation or weakly negative pressure shift above 4.0 GPa was also observed. The proposed origin of these results is the presence of repulsion between Γ-folded states in the CuPt-type ordered structure of GaInP samples, in which the ordering is not perfect nor homogeneous but rather consists of domains of ordered and disordered phases, depending on the growth conditions.