COMPARATIVE-STUDY OF PHOTOLUMINESCENCE IN ORDERED AND DISORDERED GAINP ALLOYS UNDER HIGH-PRESSURE

We have measured the photoluminescence (PL) spectra of ordered and dis ordered Ga0.5In0.5P alloys grown by metalorganic vapor phase epitaxy u nder pressures from 0 to 6 Cpa at three different temperatures (T = 12 , 77 and 300 K). At atmospheric pressure, the band-gap energy E(0), de rived from the PL spectrum, of the ordered GaInP is about 70 meV lower than that of the disordered alloy. With increasing pressure the PL sp ectrum exhibits a rapid shift toward higher energies. The band-gap ene rgy E(0) of the ordered GaInP shows a sublinear pressure dependence up to about 4 GPa, while that of the disordered alloy increases almost l inearly up to the highest pressures (3.0-3.5 GPa) beyond which the PL emission disappears. At lower temperatures (T = 12 and 77 K) the PL pe ak energy for the ordered GaInP is also found to decrease in energy fo r pressures above 4 GPa. These results can be partly related to the ex istence of the repulsion between the Gamma-folded energy states in the CuPt-type ordered structure, which affects E(0) and also the Gamma-X crossover under high pressure in these materials.