Photoluminescence spectroscopy was used to determine the temperature and compositional dependence of the interdiffusion of Al and Ga in (Al,Ga)As/GaAs superlattices. The position of the band-to-band luminescence in the superlattices was measured before and after thermal annealing. The diffusion equation was solved for a fixed value of the diffusion coefficient in order to establish the potential profile of the superlattice structure after annealing. A solution of the Schrödinger equation, where the electron or hole wave function was expanded as a Fourier series, was used to determine the position of the superlattice band edges before and after annealing and thus deduce the expected luminescence peak positions. The value of the coefficient which yielded a calculated shift which was in agreement with the measured shift in the luminescence was taken to be the actual value of the interdiffusion coefficient. For structures consisting of GaAs wells and AlxGa1-xAs barriers, where x was 1 or 0.3, the interdiffusion process was characterized by an activation energy of 6.0eV and a value of 4 x 10-19cm2/s at 850C. When x was equal to 0.7, the interdiffusion was characterized by an activation energy of 4.0eV and a value of 7 x 10-18cm2/s at 850C.

J.C.Lee, T.E.Schlesinger, T.F.Kuech: Journal of Vacuum Science and Technology B, 1987, 5[4], 1187-90