Spinodal-like decomposition of InGaAsP(100) InP grown by gas source molecular beam epitaxy

Epitaxial layers of In1−xGaxAsyP1−y have been grown lattice-matched to (100) InP substrates over a wide alloy range using gas source molecular beam epitaxy (GSMBE). Transmission electron microscopy (TEM), photoluminescence (PL), and X-ray diffraction have been used to characterize the spinodal-like decomposition of the InGaAsP layers that originates in the diffusion of adatoms at the growing surface. TEM analysis indicates that the dimensions of the spinodal structure are typically 100 Å in the [011] direction, 1000 Å in the [01̄1] direction, and 700 Å in the [100] growth direction. Compositional fluctuations as high as 2.3% in group III and V components have been derived from the PL data. Kinetic limitations of the decomposition have been studied in terms of growth temperature, total group V flux, and crystallographic direction. Decreasing the growth temperature and increasing the group V flux limits the diffusion length of the adatoms before incorporation takes place, and has been shown to decrease the decomposition of the layer during growth.