3.5 Ternary Alloys

Transport simulation of III-V ternaries (and especially AlGaN) have always suffered under the empirical nature of the alloy scattering models. As reported by Chin et al. [255] the alloy scattering is the most important scattering mechanism to consider in the ternary nitrides, as it is the only one to exhibit a "bowing" behavior with changing composition. While the other material properties [256] used in this approach are well known, the alloy scattering potential is still debated.


The alloy scattering potential was determined based on the Philips' electronegativity theory [255]. The calculations showed, that alloy scattering is extremely pronounced in InAlN and InGaN (especially at low temperatures around 77 K), while it is mostly insignificant in AlGaN. Further works neglected it [257,152], however some explored the extreme cases [153] and observed that it can become dominant for the largest predicted values of the alloy scattering potential. A convenient way to calculate the latter was chosen in [247], where a value equal to half of the AlN/GaN conduction band energy offset was used. A self-consistent approach to calculate the alloy scattering rate by fitting it to a semi-empirical energy-dependent expression was proposed in [258] and yielded good agreement with low temperature measurements. Also some experimental results from indirect measurements are already available [259].


A value of 0.6$ -$0.65 eV for the alloy scattering potential was calculated by [255] for InGaN. [260] used a slightly lower value of 0.55 eV, while [226] choose the InN/GaN conduction band energy offset as the potential.


The calculation of [255] yielded a value of 0.6 eV for the alloy scattering potential, while [226] used the InN/AlN conduction band energy offset.

S. Vitanov: Simulation of High Electron Mobility Transistors