Lateral compositional modulation in lattice-matched GaInP/GaAs heterostructures

High-resolution transmission electron microscopy has been employed to study the microstructure of GaAs lattice-matched GaInP heterostructures grown by solid source molecular beam epitaxy. It is found that the GaInP epilayers undergo lateral compositional modulation at a growth temperature of 520 deg reesC. The modulating spacing is irregular, varying between 5.0-15.0 nm. Th e compositional difference in the two decomposed phases is estimated betwee n 0.14-2.1 at.%, which is far from thermal equilibrium. High-resolution TEM observation shows that, corresponding to the contrast modulation, there ex ist considerable lattice distortions nearly parallel to the growth directio n inside the GaInP epilayers. Ln the distorted regions, dislocations of 60 degrees -type are frequently observed. Factors that may contribute to the c ompositional modulation are discussed.