Si/SiGe n-type inverted modulation doping using ion implantation

Abstract

Inverted modulated-doped Si/Si1−xGex wafers have been prepared using ex-situ ion implantation of a virtual substrate for the doping followed by cleaning and the regrowth of the silicon quantum well in the growth system. This fabrication scheme attempts to circumvent the main problem in the growth of inverted modulation doped structures by chemical vapour deposition, which is the surface segregation and diffusion of n-type dopant causing high dopant densities in all subsequent layers after the introduction of n-type dopant to the growth chamber. Magneto-transport results will be shown for modulation-doped field effect transistor (MODFET) samples which have 1.7 K mobilities up to 73 000 cm2/V s for carrier concentrations of 4.25×1011 cm−2. Clear Shubnikov-de Haas oscillations and quantum Hall effect plateaux are visible demonstrating the quality of the samples produced using the technique.