The results of S-dH measurements and the observation of quantum Hall plateaus at 1.5 K clearly demonstrated the existence of a 2DEG in modulation-doped AlxGa1-xAs/InyGa1-yAs/GaAs asymmetric step quantum wells. The PL data measured at several temperatures showed that the excitonic transition from the ground electronic subband to the ground heavy-hole band (E-0-HH1) shifted to the lower energy side with increasing temperature. The value of the (E-0-HH1) excitonic transition obtained from the PL measurements was in reasonable agreement with that determined from self-consistent calculations. (C) 2002 Elsevier Science Ltd. All rights reserved.