The effect of pressure on the band-gap energy in ordered GaInP and AlGaInP grown by MOVPE

Abstract

Photoluminescence (PL) measurements on Ga0.52In0.48P and Al0.18Ga0.34In0.48, P alloys, grown by metalorganic vapor phase epitaxy (MOVPE) on GaAs, have been made as a function of pressure up to about 4.5 GPa at 77 K. The substrates are oriented on the (100) and off the (100) plane toward [011] and [011̄] by up to 25 °. The band-gap energy anomaly in the CuPt-type ordered structure has been systematically investigated at high pressures. With increasing pressure the E0 band gap shows a sublinear shift toward higher energies. For some samples, this shift tends to saturate, of the PL peak shows a decrease in energy with pressure. The pressures needed for these observations are found to be significantly smaller in AlGaInP than in GaInP. The observed behaviors strongly depend on substrate misorientation, and hence reflect the degree of ordering in these alloys. These results clearly demonstrate the importance of the effects of repulsion between the Γ-folded energy states on the optical spectra in the CuPt-type ordered structure. Possible explanations for some of the trends in high-pressure behavior of the E0 direct band gap in GaInP and AlGaInP samples having different degrees of ordering are discussed, including the modification of the ordinary Γ-X crossover upon ordering. © 1995.