Mobility of Holes in Nanometer Ge-on-Si p-Type Metal-Oxide-Semiconductor Field-Effect Transistors at Low Temperatures

We investigated magnetoresistance of p-type Ge-on-Si metal-oxide-semiconductor field-effect transistors in order to determine the hole mobility mu as a function of the gate polarization (V(G)). Measurements were carried out at 4.2 K and magnetic fields up to 10 T. The signal measured was proportional to the derivative of the transistor resistance with respect to V(G). To determine the hole mobility we developed a method to treat the measured signal which is based on a numerical solution of a differential equation resulting from the theoretical description of the experimental procedure. As a result, we obtained a non-monotonic mu(V(G)) dependence which is a characteristic feature of the carrier transport in gated two-dimensional structures.