Temperature dependent low-field 2DEG mobility in Sc_xAl_1-xN/GaN-based HEMT

The demand for high-temperature electronics is rapidly increasing, driven by applications in electric vehicles and energy systems. These environments require devices capable of operating at higher frequencies and power under extreme thermal conditions. While AlGaN/GaN HEMTs are ideal for high-power, high-frequency, and high-temperature electronics, it faces limitations in terms of temperature stability, and rapid reduction in mobility. Consequently, alternative materials like ScAlN/GaN HEMTs with high 2DEG densities are being explored. This study employs first-principles based electron-phonon interaction to examine low-field mobility in Sc_xAl_1-xN/GaN HEMTs across a range of temperatures and Sc compositions. We include ab-initio calculated electron-phonon scattering, including contributions from polar optical phonons (POP), piezoelectric (quadrupole corrected), non-polar, inter-subband scattering and interface roughness (IFR) scattering. Results indicate that IFR limits performance at low temperatures, while POP scattering dominants at elevated temperatures. Moreover, increasing Sc content raises 2DEG density and enhances wavefunction confinement, intensifying IFR effects and reducing mobility. To validate our model, we grew Sc_0.15Al_0.85N/GaN HEMT by MBE and measured Hall mobility over a range of temperatures. The measured mobilities match closely with the calculated data. Using these validated models, we gain insight into the physical processes limiting device performance across temperature ranges.