Transport modeling in gallium nitride materials and devices based on full-band cellular Monte Carlo simulation

A full-band Cellular Monte Carlo (CMC) simulator for wurtzite GaN was developed to investigate the electronic transport properties in bulk materials and devices. A full calculation of the electron-phonon scattering rate of wurtzite GaN is performed in this simulator using the rigid pseudo-ion model. The results show that the deformation potential has a large anisotropic behavior. Anisotropic polar optical phonon scattering, ionized impurity scattering, piezoelectric scattering, and dislocation scattering are also considered. The calculated velocity-field characteristics show good agreement with recent experimental data.; This CMC simulator has been applied to simulate electron transport in a GaN Metal Semiconductor Field Effect Transistor (MESFET) device on a sapphire substrate. The calculated I-V characteristics were higher than the experimental room temperature data. However, the inclusion of a thermal correction shows good agreement with the experimental data. This result shows that consideration of self-heating effects is essential in modeling GaN devices on lower thermal conductivity materials, such as sapphire substrates.; AlGaN/GaN High Electron Mobility Transistors (HEMTs) were also investigated. Polarization effects at the interface were included, and quantum corrections were applied to the hetero-interface through an effective potential approach. Optimal effective potential parameters were obtained for different Al contents in the AlGaN layer, and for different gate biases. The CMC simulator coupled with these quantum corrections was applied to simulate a 0.25 mum AlGaN/GaN HEMT fabricated on a silicon carbide substrate. The results show good agreement with the experimental DC current-voltage characteristics.; A RF analysis of the AlGaN/GaN HEMT was also carried out using the CMC simulator. Fourier decomposition (FD) and the monochromatic sinusoidal excitation were performed and compared, and show good agreement with one another. The calculated frequency response was higher than the experimental data by a factor of two. Thermal calculations shoved that thermal effects are small. A preliminary investigation of non-equilibrium phonon effects was performed for the same device. These preliminary results suggest that non-equilibrium phonon effects might play an important role in reducing the HEMT device RF performance, due to the high sheet carrier density and high electronic field in AlGaN/GaN HEMTs, which amplifies non-equilibrium phonon effects.