Electronic Structure and Carrier Transport Analysis in <tex>$\beta$</tex> -Ga<inf>2</inf>O<inf>3</inf> Using a Two-Valley Ensemble Monte Carlo Framework

Abstract

We carry out two-valley ensemble Monte Carlo (EMC) simulations for the calculation of electron mobility in $\beta-$ Ga 2 O 3 . First, the electronic bandstructure is determined using first-principles density function theory (DFT) as available in the open-source Quantum Espresso package. A Perdew-Zunger LDA exchange-correlation function generated ultrasoft pseudopotential was used in the calculations. The following electron scattering mechanisms are found to be important: acoustic deformation potential, ionized impurity, and polar optical phonons (POP). In $\pmb{\beta-\mathrm{Ga}_{2}\mathrm{O}_{3}}$ , low crystal symmetry induces multiple phonon modes, which complicates the mobility calculation. Here, 50 meV of POP energy was found to be good enough for the Frohlich scattering model. For low electrical fields at 300K, we report an electron mobility of 113 cm2/V·s. Also, in the range of 150K-500K, our simulation results match very well with reported Hall mobility data. For high electrical fields, $\pmb{\beta-\text{Ga}_{2}\mathrm{O}_{3}}$ displays a negative differential mobility (NDM). Critical electrical field is found to be 250 KV/cm with a maximum steady-state drift velocity of 2.2×105m/s. Finally, for a realistic device with an $\mathbf{Al}_{2}\mathbf{O}_{3}/\beta-\mathbf{Ga}_{2}\mathbf{O}_{3}$ interface, the influence of surface roughness scattering (SRS) was studied via Ando's model. Results show that electron mobility in $\pmb{\beta-\text{Ga}_{2}\mathrm{O}_{3}}$ dramatically decreases with the inclusion of SRS.