MINIMOS-NT is a general-purpose semiconductor device simulator providing steady-state, transient, and small-signal analysis of arbitrary two- and three-dimensional device structures. The first approach to study a heterostructure device using MINIMOS-NT dates back to the 90s, when mobility models for GaAs and extended recombination/generation models were implemented . Simultaneously interface models for heterojunctions (i.e. a thermionic field emission model) were developed . Using the extended software tool a simulation setup for the optimization of GaAs-based HEMTs was established, which delivered results in good agreement with experimental data and allowed predictive device simulation . Work on heterojunction devices continued in this decade: both HBT and HEMT structures were analyzed [136,137]. A consistent set of model and model parameters was achieved, which best described the physical behavior of both III-V HEMTs and HBTs . Work was focused on several pseudomorphic AlGaAs/InGaAs/GaAs and InAlAs/InGaAs HEMT technologies, while device optimization was conducted with respect to statistical process variations. Additionally, three-dimensional thermal simulations of III-V HEMTs were conducted in order to help thermal investigations. Accordingly, impact ionization and self-heating were included in the simulation. Additionally, small signal S-parameters were extracted from AC simulations. The first performed simulation of a GaN HEMT with MINIMOS-NT showed a good agreement with measurements .