Anomalous Electroreflectance Spectrum of Spontaneously Ordered Ga0.5In0.5P

The electroreflectance spectrum of spontaneously ordered Ga _0.5In_0.5P contains two extra features at energies near 2.2 and 2.35 eV. The energies and intensities of these transitions are shown to be dependent on growth temperature and substrate misorientation. The possible origins of the two transitions are explored. The analysis shows that the transition at about 2.35 eV exhibits shifts consistent with those expected for Ga_0.5In_0.5P with ordered {111} planes. The second transition is shown to be unexpected and is not conclusively assigned. However, a possible assignment is identified, implying that a complete understanding of spontaneously ordered Ga_0.5In_0.5P may require simultaneous consideration of two different types of order.