AbstractQuantum (single particle) and classical (transport) scattering times have been measured and analyzed as a function of density of the two‐dimensional electron gas (2DEG) in pseudomorphic AlGaAs/InGaAs/GaAs heterostructures. Hydrostatic pressure was used to decrease and infrared LED light pulses to increase the 2DEG density. Our experimental results allow us to distinguish two different persistent photoionization mechanisms induced by the light pulses, which have quite different effects on the two kinds of scattering times. We have also found evidence that a modification of the spatial correlation of charges on remote donors in the barrier (by means of pressure and/or illumination by light pulses) affects the quantum lifetime much more than the transport scattering time.