Minority carrier injection at forward‐biased WNx/n‐GaAs Schottky gates lead to diffusion capacitances in excess to the space charge capacitance and inductive reactances in certain frequency ranges.p‐buffer layers act as a minority carrier sink which enhances the minority carrier injection. This finally gives stronger excess capacitances and inductive reactances. Furthermore, excess diffusion capacitances can be observed at higher frequencies. The frequency dependent admittance behavior of forward biased WNx/n‐GaAs gates is studied in the temperature range between 77 K and room temperature.