InGaAs/AlAs quantum wells on GaAs substrates were studied for near-infrared intersubband transitions. The relationships between the properties of the intersubband absorption and the structural/growth conditions of the quantum wells were quantitatively investigated by using theoretical calculations based on ak-pperturbation method. The total intersubband absorption magnitude is shown to be closely related to the leakage of free carriers from the &Ggr; minimum of the well to theXminimum of the barrier. This work provides important information for design of devices utilizing short wavelength intersubband transitions. ©1997 American Institute of Physics.