We investigated here the GaAs(d1 = 184 Å)/Al0.18Ga0.82As (d2 = 42 Å) multiple quantum wells based on our enhanced numerical calculations in the envelope function formalism. We calculated the band structures and the effective mass mi* of charge carriers. When the well thickness d1 increases, the bandgap Eg decreases like m*. The calculated Fermi level energy and the density of states show n-type conductivity and a quasi-two-dimensional transport character. When the barrier thickness d2 increases the bandwidth decreases as a result of the weakening of interlayer tunnelling along the growth direction in the first Brillouin zone. We also interpreted theoretically the Shubnikov-de Haas and quantum Hall effects measurements reported by B. G. Tavares et al. These results are necessary for the design and engineering of multiple quantum wells infrared detectors.