Measurements of gate voltage dependence of electron mobility in δ-doped HFET´s

The results of the measurements of the gate voltage dependence of the electron mobility in heterostructure field effect transistors (HFETs) using a split C-V technique are discussed. This method allows one to deduce this dependence without making any assumptions about other parameters such as the threshold voltage. The dependence of the electron mobility in the HFET channel on the gate voltage depends on the heterointerface quality. In some samples, the mobility increases with the increase of the gate voltage. In other samples (grown on a different molecular beam epitaxy machine), the mobility drops to nearly a half of its maximum value at high gate voltages. This means that, in these samples, the electron mobility is strongly dependent on the transverse electric field (similar to analogous behavior in p- and n-channel MOSFETs)