Non-equivalence of direct and reverse interfaces in AlAs-GaAs superlattice structures as evidenced by X-ray diffraction

Abstract In this paper we study the relation between interface roughness and X-ray intensity diffracted by a short period n 1 (AlAs)- n 2 (GaAs)/GaAs(001) superlattice (SPSL). A theoretical approach shows that introducing the same graded composition profile on both sides of the GaAs well equally reduces the intensity of all high order satellites. However, if the profile is not the same at both interfaces, the intensity variation of the satellites is completely different, depending on their order. We show that the extinction rule of satellites is no longer valid and therefore constitutes a very sensitive criterion of the non-equivalence of the direct and reverse interfaces. As an example, we apply this criterion to refine the structure of 8(AlAs)-20(GaAs) SPSL. The best agreement between observed and calculated SL structure factors is obtained for an asymmetric-shape GaAs well. The interface widths are 6 and 4 monolayers, and the best-fit model gives an R factor of 0.028.