Competing strain relaxation mechanisms in organometallic vapor-phase epitaxy of strain-compensated GaInP/InAsP multilayers on InP(001)

The strain relaxation of strain-compensated GaInP/InAsP multilayers grown on InP(001) has been studied as a function of misfit strain f, number of periods N, and growth temperature Ts. X-ray reciprocal lattice maps indicate globally fully strained structures while transmission electron microscopy observations show coherent buffer-layer/multilayer interfaces. The full width at half maximum intensity of the superlattice peaks in high-resolution x-ray diffraction 004 ω–2θ scans (Γω–2θ) decreases with increasing N (up to N=50) for structures with |f|=0.50% grown at Ts=620 °C as expected for multilayers of high crystalline quality. In contrast, Γω–2θ increases with N for structures with |f|=0.75% due to interface nonhomogeneities when N=20 and dislocations when N=50. Structures with |f|=0.75% and N=20 grown at Ts=650 °C showed long-wavelength thickness modulations of very small amplitude with no evidence of extended defects. For Ts=680 °C, strong thickness undulations with peak-to-cusp amplitude of ≃50 nm after 20 periods and lateral wavelength of ≃550 nm lead to dislocation nucleation in highly strained regions.