Quantum engineering of nanoelectronic devices: the role of quantum confinement on mobility degradation

Transport properties in semiconductor nanostructures, spanning nanometer di mensions comparable to the de Broglie wavelength of charge carriers, are sh own to depend upon the geometry of confinement as quantum waves are encount ered. Approximate wave functions are obtained for prototype AlxGa1-xAs/GaAs /AlxGa1-xAs quantum wells (QWs) with finite boundaries that depend on the a lloy composition x and those in MOSFET that depend on the applied gate elec tric field. The leakage of the wave function in classically forbidden regio ns is accounted for by an enhanced effective width in an equivalent model w ith infinite boundaries. By relative comparison of the transport parameters obtained in rectangular quantum well (RQW) and triangular quantum well (TQ W), we convincingly show that the mobility degradation is a direct result o f quantum confinement, in direct contrast to a model that predicts it as be ing degraded due to electrons becoming hot. The gate capacitance as well as transport in the quasi-free direction is affected by the quantum confineme nt as wave function peaks at a distance removed from the interface while va nishing at the interface. (C) 2001 Elsevier Science Ltd. All rights reserve d.