VALENCE-BAND SPLITTING IN ORDERED GA0.5IN0.5P STUDIED BY TEMPERATURE-DEPENDENT PHOTOLUMINESCENCE POLARIZATION

Valence-band splitting due to symmetry breaking in long-range-ordered Ga0.5In0.5P alloys grown on (001) GaAs by organometallic vapor-phase e pitaxy has been systematically investigated with photoluminescence (PL ) polarization spectroscopy. PL spectra measured along the [110] and [ 110BAR] directions showed anisotropy in both the peak energy and inten sity together with a significant reduction of the peak energy. It has been found that the anisotropy in polarized PL spectra originates from the valence-band splitting between GAMMA(4-upsilon), GAMMA(5-upsilon) , and GAMMA(6-upsilon) induced by symmetry breaking due to spontaneous CuPt-type long-range ordering of Ga0.5In0.5P. On the basis of theoret ical treatments of optical transition rates in the ordered crystal, a general formula describing the relative integrated intensity in PL pol arization spectra has been obtained. According to this formula, the va lence-band splitting energy has been estimated by measuring the temper ature dependence of the polarized PL intensity. The correlations betwe en the anisotropic PL and crystal-growth conditions such as growth tem perature and gas-flow ratio in the input column-V and column-III sourc es are also discussed.