COMPOSITIONAL DISORDERING OF INGAAS GAAS HETEROSTRUCTURES BY LOW-TEMPERATURE-GROWN GAAS-LAYERS/

Compositional disordering of InGaAs/GaAs superlattices using a low-tem perature-grown GaAs cap layer (LT-GaAs) by molecular beam epitaxy has been studied. The disordering of the superlattice was verified by phot oluminescence and double-crystal x-ray rocking curve measurements. The Ga-vacancy-enhanced interdiffusion due to the presence of LT-GaAs was found to be the disordering mechanism. Diffusion equations and the Sc hrodinger's equation were solved numerically to obtain the composition profile and the transition energies in the disordered quantum well, r espectively. The simulated energy shifts for samples under different a nnealing conditions agreed very well with the experimental results. Th e calculated effective diffusivity for the In-Ga interdiffusion has an activation energy of 1.63 eV, which is smaller than the activation en ergy 1.93 eV, for intrinsic interdiffusion. The diffusivity for the en hanced In-Ga interdiffusion due to the presence of LT-GaAs is about tw o orders of magnitude larger than the intrinsic In-Ga diffusivity. (C) 1996 American Institute of Physics.