Large-signal modeling and characterization of high-current effects in indium gallium phosphide/gallium arsenide HBTs

High-current effects in InGaP/GaAs HBTs were modeled and characterized. In addition to cause self-heating, high currents were found to degrade large-signal performance mainly through Kirk (base push-out) and quasi-saturation effects. It was found that the base push-out mechanism is responsible for decrease of f_T at medium currents while the quasi-saturation is the cause for fast reduction of f_T in the high current region under the static biasing conditions. For the first time Kirk effect parameters were extracted at a very high current densities under the semi-isothermal conditions.; New formalisms in terms of base transit time and base-collector diffusion capacitance were developed. A complete electrical static-dynamic temperature-dependent conventional BJT Gummel-Poon Model was revised and adopted to account for HBT-specific device physics. The new large-signal model for HBTs was incorporated into the commercial RF circuit simulator. This new model was verified against large-signal characteristics measured at 2 GHz under different load impedances. The validity of the new model for HBTs of different emitter geometry was also explored.; Ways of improving device performance from the technological standpoint were suggested.