QUANTUM AND TRANSPORT MOBILITIES OF ELECTRONS IN GAAS GA1-XALXAS MULTIPLE-QUANTUM WELLS/

The quantum and transport mobilities of electrons in modulation-doped GaAs/Ga1-xAlxAs multiple quantum wells with well widths in the range b etween 51 and 145 Angstrom and carrier density of about 1 x 10(16) m(- 2) have been investigated by magnetotransport measurements. The magnet ic field dependence of the amplitude of the quantum oscillations in bo th magnetoresistance and Hall resistance have been used to determine t he quantum (tau(q)) and transport (tau(t)) lifetimes (and hence the qu antum (mu(q)) and transport (mu(t)) mobilities) of 2D electrons. The v alues thus found for mu(t) are substantially smaller than those of the Hall mobility (mu(H)) as obtained in the ohmic regime at low magnetic fields. The discrepancy between mu(t) and mu(H) has been explained in terms of a transport lifetime tau(t) that depends on the electron ene rgy due to the scattering of electrons by interface roughness in the q uantum wells.