GATED HALL-EFFECT MEASUREMENTS IN HIGH-MOBILITY N-TYPE SI/SIGE MODULATION-DOPED HETEROSTRUCTURES

We report gated Hall effect measurements and the study of electron mobility versus density in high-mobility modulation-doped Si/SiGe heterostructures. Front and back gates have been used to control the electron density and the shape of the electron wave function in the strained Si channel. The gate control on the electron density is modeled using a self-consistent Schrödinger and Poisson equation solution. We find that the electron mobility μ increases with electron density n as μ∝nα, where α is 1.2-1.8 at low n, and 0.7-1.0 at high n. A peak mobility of 5.2×105cm2/V s at 0.4 K, considerably higher than the value in comparable ungated structures, is achieved when the electron wave function is moved away from the top heterointerface towards the center of the Si channel.© 1995 American Institute of Physics.