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 Angstrom in the [011] direction, 1000 Angstrom in the [0 $($) over bar$$ 11] direction, and 700 Angstrom 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.