3.2 Material Models

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 [207] and in a simplified modeling approach pseudomorphic AlGaAs/InGaAs HEMTs have been simulated using MINIMOS-NT[50]. 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.

Table 3.1: Minimum valley as a function of material composition.

Material Composition Range Minimum Composition Range Minimum References         AlGaAs 0-0.45 0.45-1 X [250] InGaAs 0-1 - -   InAlAs 0-0.3 X 0.3-1 [113] AlGaN 0-0.4 - - [158]

• 3.2.1 Mass Density
• 3.2.2 Permittivity
• 3.2.3 Band Structure Parameters
  • 3.2.3.1 The Band Gap
  • 3.2.3.2 Band Gap Offsets
  • 3.2.3.3 Effective Carrier Masses
  
  
• 3.2.4 Effective Density of States
• 3.2.5 Carrier Mobility
  • 3.2.5.1 Low Field Mobility
  • 3.2.5.2 Semiconductor Alloys
  • 3.2.5.3 High Field Mobility for the Drift-Diffusion Equation
  • 3.2.5.4 High Field Mobility for Hydrodynamic Model
  • 3.2.5.5 Alternative High Field Mobility Model
  
  
• 3.2.6 Saturation Velocity
• 3.2.7 Energy Relaxation Times
• 3.2.8 Shockley-Read-Hall Generation/Recombination
• 3.2.9 Direct Generation/Recombination
• 3.2.10 Auger Generation/Recombination
• 3.2.11 Impact Ionization
  • 3.2.11.1 Impact Ionization for the Drift-Diffusion Transport Model
  • 3.2.11.2 Hydrodynamic Impact Ionization Model
  • 3.2.11.3 Simplified Hydrodynamic Model