Effect of parasitics on electrochemical capacitance-voltage profiling of pseudomorphic high electron mobility transistor structures

The effect of parasitic series resistances on electrochemical capacitance-voltage (EC-V) profiling is simulated numerically for AlxGa1-xAs/InyGa1-yAs pseudomorphic high electron mobility transistor (p-HEMT) structures. The actual EC-V measurement is simulated numerically by reconstructing the charge distribution from an intrinsic distribution calculated from a self-consistent k.p model. The calculated charge distribution then forms the basis for examining the possible profiles an EC-V measurement would produce when parasitics are taken into account. From a simple lumped-circuit model, it is shown that parasitic resistances distort the shape of the charge distribution by changing the relative heights of the delta-layer and channel charges. Hysteresis effects may also occur and may be accompanied by a change in material type from n to p even though the material is known to be n-type over the entire range of measurement. Additionally, an undesirable dependence of the charge profile on the probe signal frequency is found.