In this section the models are described that define and distinguish the relevant III-V materials used. Using a similar set of parameters AlGaAs/GaAs and InGaP/GaAs HBTs  and in a simplified modeling approach pseudomorphic AlGaAs/InGaAs HEMTs have been simulated using MINIMOS-NT. Special effort was made to obtain an extended and more complete set of parameters for a wide range of material compositions and new materials systems. In the modeling concept applied the ternary materials are composed from their binary constituents using a second order interpolation. Table 3.1 shows the naming convention of the ternary materials and the energetic order of the valleys in k-space as a function of material composition. For AlGaN the investigations are restricted so far to the situation of the valley having a direct band gap due to uncertainties in the band structure [103,158], which is sufficient for all technically relevant AlGaN/GaN HEMTs.