Systemic Investigation of Ga2O3 from Material to Device

Author

zichang zhang, Southern Illinois University CarbondaleFollow

Date of Award

12-1-2020

Degree Name

Doctor of Philosophy

Department

Electrical and Computer Engineering

First Advisor

Ahmed, Shaikh

Abstract

Ga2O3, which is a novel and ultra-wide band gap oxide semiconductor material, has attracted more and more attention due to its chemical and thermal stability and various potential applications to devices. This dissertation focuses on systemic investigation of β-Ga2O3 and ε- Ga2O3 from fundamental material properties, device modeling and verification of circuit performance. ab initio calculation was employed to do theoretical investigation of material properties. Based on Generalized Gradient Approximations (GGA), we calculate the band structure, effective mass of electron, density of states and phonon band structure. However, calculated band gap is only 2.36 eV and 2.16 eV, which is much lower than experimental measured value. In order to overcome the underestimation, the GGA+U method was carried out for both materials. band gap as 4.8 eV and 5.0 eV are finally identified, which have a good agreement with experimental results. Device simulation is done with Monte Carlo (MC) method and Drift-Diffusion method. Firstly, we used traditional ensemble MC to calculate the mobility of bulk material. We found conventional phonon scattering model cannot capture electron-phonon interaction (EPI) very well due to complex phonon structure of β-Ga2O3. Therefore, a refined MC method was proposed. By including multi-phonon scattering model, the refined MC works very well with multi-phonon modes EPI. The calculated mobility of bulk material is 118 cm2/(V•s), which is close to measured 120 cm2/(V•s). Using obtained mobility, the performance of depletion-mode β-Ga2O3 MOSFET was simulated in Silvaco TCAD.