Occurrence of CuPt-A and CuPt-B type ordering in GaInP layers grown by solid source molecular beam epitaxy

Transmission electron diffraction (TED) and reflection high-energy electron diffraction (RHEED) have been used to investigate GaInP molecular beam epitaxial layers grown at temperatures in the range 445–510°C. TED results reveal the presence of diffracted intensity at 12(−1 1 1) and 12(1 −1 1) positions, indicating the occurrence of CuPt-B ordering. As the growth temperature decreases, the superlattice spots move toward 12{−1+δ,1−δ,0} positions, where the value of δ is 0.15. It is further shown that for the layers grown at temperatures in the range 445–490°C, weak diffracted intensity is observed at 12(1 1 −1) and 12(1 1 1) positions, indicating the formation of CuPt-A ordering. Based on the TED and RHEED results, explanations are given to describe the formation of CuPt-A and CuPt-B type ordering. Photoluminescence results show that the samples grown at temperatures in the range 470–510°C undergo a bandgap reduction. This is attributed to the presence of ordered structures and composition modulation.