WELL-WIDTH DEPENDENCE OF THE INPLANE EFFECTIVE-MASS AND QUANTUM LIFETIME OF ELECTRONS IN GAAS GA1-XALXAS MULTIPLE-QUANTUM WELLS/

The electronic properties of modulation-doped GaAs/Ga1-xAlxAs multiple quantum wells (MWQ) with well width (L-z) in the range between 51 and 145 Angstrom have been investigated by using the Shubnikov-de Haas (S dH) oscillations technique. The carrier density and the Fermi energy h ave been determined from the period of the SdH oscillations. The in-pl ane effective mass (m) and the quantum lifetime (tau(q)) of 2D electr ons have been obtained from the temperature and magnetic field depende nces of the SdH amplitude. For narrow MQW samples (L-z = 51, 75 and 78 Angstrom), m increases with decreasing L-z; for the samples with L-z = 106 and 145 Angstrom, m is approximately equal to that of electron s in bulk GaAs. The values obtained for tau(q) show no clear well-widt h dependence and suggest that interface roughness is the dominating sc attering mechanism in GaAs/Ga1-xAlxAs MQWs.