Impact ionization phenomena in AlGaAs/GaAs HEMTs

Abstract
The impact ionization current in AlGaAs/GaAs HEMT's is evaluated by means of measurements of the gate current at high drain voltages. A previously reported method to calculate impact ionization coefficient in GaAs MESFET's is extended to HEMT's. Results agree with the hypothesis that impact ionization takes place nearly exclusively in GaAs, and closely follow previously reported data for the electron impact ionization coefficient in GaAs