A Rigorous Model of Tunneling and Thermionic Currents in Microwave HFETs

A new model is presented to simultaneously calculate both tunneling and thermionic currents over the heterojunction and over the Schottky barrier (metal-semiconductor contact). The energy band diagram, the subband energies, and the corresponding wave functions are obtained by self-consistent solution of Poisson´s and Schroedinger´s equations (SCSPS). The differences between the quasi Fermi levels at the heterojunction and at the metal contact which control the currents are accurately obtained by equating the total current over the heterojunction with the total current over the Schottky barrier. The model is applied to calculate the gate current in typical hetero-FET structures and the obtained results are compared with experimental data.