A PHYSICS-BASED FITTING AND EXTRAPOLATION METHOD FOR MEASURED IMPACT IONIZATION COEFFICIENTS IN III-V-SEMICONDUCTORS

A general approach based on a physical model of impact ionization to fit and extrapolate measured ionization coefficients of electrons-alpha and holes-beta in III-V semiconductors is described. Materials being considered include GaAs, AlxGa1-xAs (x=0.1-0.4), InP, In0.53Ga0.47As, and In0.52Al0.48As. Expressions giving the correct dependencies are obtained at very large or small electric fields outside the range of most measurements while at the same time a reasonable fit is achieved for experimental data. The results of the proposed approach yielded a set of physical parameters, which can be coupled with the temperature-dependence relationships in the model to predict impact ionization coefficients over a wide range of electric fields at different temperatures, and can be useful in calculations of temperature-dependent avalanche breakdown voltages of electronic and optical devices.