MAGNETOTRANSPORT IN INAS/ALSB QUANTUM-WELLS WITH LARGE ELECTRON-CONCENTRATION MODULATION

We report measurements of magnetocapacitance, Hall resistance, and magnetoresistance of gated InAs/AlSb quantum wells. By varying the voltage between the front gate and the two-dimensional electron gas, we were able to make magneto-transport measurements at 4.2 K for electron concentrations covering a range from 3 x 10(11) to 3 x 10(12) cm-2. A strongly modified magnetocapacitance signal and a drop in the mobility were observed as the second subband became populated. The relation of gate voltage to density of mobile carriers obtained from these measurements was in agreement with the simple capacitor model, indicating the absence of Fermi level pinning in the quantum well.