AN ENERGY TRANSPORT MODEL FOR HBTS USING ENERGY‐ AND COMPOSITION‐DEPENDENT TRANSPORT PARAMETERS

In this paper, we describe an energy transport simulation method for graded AlGaAs/GaAs HBTs, which uses Al composition‐, doping density‐, and energy‐dependent transport parameters estimated by a Monte Carlo method. For several representative Al composition x and doping densities, parameters such as electron mobility, energy relaxation time and upper valley fraction are evaluated as a function of electron energy. For the other x, these are determined by linear extraporation. The problem of this extraporation method is also described. Calculated cutoff frequency characteristics and electron velocity profiles are compared with those by using more simplified approaches, indicating the importance of using adequate transport parameters.