The mobility of two-dimensional electron gas in AlGaN/GaN heterostructures with varied Al content

The mobility of the two-dimensional electron gas (2DEG) in AlGaN/GaN heterostructures changes significantly with Al content in the AlGaN barrier layer, while few mechanism analyses focus on it. Theoretical calculation and analysis of the 2DEG mobility in AlGaN/GaN heterostructures with varied Al content are carried out based on the recently reported experimental data. The 2DEG mobility is modeled analytically as the total effects of the scattering mechanisms including acoustic deformation-potential, piezoelectric, polar optic phonon, alloy disorder, interface roughness, dislocation and remote modulation doping scattering. We show that the increase of the 2DEG density, caused by the ascension of the Al content in the barrier layer, is a dominant factor that leads to the changes of the individual scattering processes. The change of the 2DEG mobility with Al content are mainly determined by the interface roughness scattering and the alloy disorder scattering at 77 K, and the polar optic phonon scattering and the interface roughness scattering at the room temperature. The calculated function of the interface roughness parameters on the Al content shows that the stress caused AlGaN/GaN interface degradation at higher Al content is an important factor in the limitation of the interface roughness scattering on the 2DEG mobility in AlGaN/GaN heterostructures with high Al content.