Structural and optical properties of Ga_xIn_1-xP layers grown by chemical beam epitaxy

Chemical beam epitaxial (CBE) Ga_xIn_1-xP layers (x ≈ 0.5) grown on (001) GaAs substrates at temperatures ranging from 490 to 580°C have been investigated using transmission electron diffraction (TED), transmission electron microscopy, and photoluminescence (PL). TED examination revealed the presence of diffuse scattering 1/2{111}_B positions, indicating the occurrence of typical CuPt-type ordering in the GaInP CBE layers. As the growth temperature decreased from 580 to 490°C, maxima in the intensity of the diffuse scattering moved from 1/2{111)_B to 1/2{-1+δ,1-δ,0) positions, where δ is a positive value. As the growth temperature increased from 490 to 550°C, the maxima in the diffuse scattering intensity progressively approached positions of 1/2{110), i.e., the value of δ decreased from 0.25 to 0.17. Bandgap reduction (∼45 meV) was observed in the CBE GaInP layers and was attributed to the presence of ordered structures.