Type II double barrier AlxGa1-xAs/AlAs/GaAs quantum wells with ultra-thin AlAs layers (1 or 2 monolayers (ML) wide) have been studied by photoluminescence as a function of the substrate misorientation. A blue shift of the recombination lines is observed when double barrier quantum wells are grown on vicinal surfaces. This is interpreted as an additional lateral confinement induced by the step array on the electron states in the AlAs layers. For structures with 1 ML of AlAs, evidence of the influence of the step array disorder on the ''QWire'' confinement energy is given.