The compositional disordering of superlattices which had been grown by means of molecular beam epitaxy, using a low-temperature GaAs cap layer, was studied. Disordering of the superlattice was verified by photoluminescence and double-crystal X-ray rocking curve measurements. The disordering mechanism was found to involve Ga vacancy-enhanced interdiffusion, due to the presence of the low-temperature GaAs. The diffusion and Schrödinger’s equations were solved numerically in order to obtain the compositional profile and the transition energies in the disordered quantum well, respectively. The simulated energy shifts for samples under various annealing conditions agreed well with experimental data. The calculated effective diffusivity for In-Ga interdiffusion involved an activation energy of 1.63eV. This was smaller than the activation energy, of 1.93eV, for intrinsic interdiffusion. The diffusivity for the enhanced In-Ga interdiffusion, due to the presence of low-temperature GaAs, was some 2 orders of magnitude larger than the intrinsic In-Ga diffusivity.

J.S.Tsang, C.P.Lee, S.H.Lee, K.L.Tsai, C.M.Tsai, J.C.Fan: Journal of Applied Physics, 1996, 79[2], 664-70