We present full band Monte Carlo simulations of a wurtzite Al0.15Ga0.85N/GaN modulation-doped field-effect transistor (MODFET). We found that without inclusion of the piezoelectric effect, the electron concentrations in the channel are much lower than obtained from experimental data. The calculated Ids-Vds curves show a strong negative differential resistance, which is a feature observed in experimental devices. Self-heating effects are usually believed to be the main cause of the negative differential resistance. Our simulations do not include self-heating, and this would indicate that at least part of what is observed is also caused by the drift-velocity behavior vs. electric field of the narrow conduction channel. For a 0.2 μm gate MODFET, the simulations yield a maximum trans-conductance Gm ≈ 250 mS/mm with VG = 1.0 V and Vds = 5.0 V. When VG = 0.0 V and Vds = 8.0 V, we obtain a maximum cutoff frequency fT = 180 GHz with Id = 1159 mA/mm.
- Monte Carlo methods
- gallium nitride
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Atomic and Molecular Physics, and Optics
- Modeling and Simulation
- Electrical and Electronic Engineering