C-V and J-V investigation of HfO2/Al2O3 bilayer dielectrics MOSCAPs on (OW) β-Ga2O3

In this letter, MOS capacitors with bilayer dielectrics consisted of large bandgap Al2O3 and high-k HfO2 in different stacking order on n-type doped (100) beta-Ga2O3 are investigated through C - V and J - V measurement. The C - V measurement results reveal that incoming HfO2 makes both bilayer structures attain an increasing dielectric constant, which means a better gate control ability in transistors comparing with single Al2O3. Additionally, the interface state density extracted by high-low frequency capacitance method suggests that Al2O3/(100),6-Ga2O3 with no treatment shows a comparative DA value (8.0 x 10(12) cm(-2) eV T-1 to 2.2 x 10(11) cm(-2) eV(-1)) with HfO2/(100), beta-Ga(2)0(3) (8.4 x 10(12) cm(-2)eV T-1 to 1.0 x 10(11) cm(-2) eV(-1)) in energy range of 0.2 to 0.9 eV. Furthermore, HfO2/Al2O3/Ga2O3 showing a bigger forward breakdown voltage of 11.0 V than 7.8 V of Al2O3/HfO2/Ga2O3 demonstrates that inserted larger bandgap Al2O3 insulator between Ga2O3 semiconductor and high-k HfO2 dielectric can prevent gate leakage current more effectively. Accordingly, the HfO2/Al2O3/Ga2O3 can enhance gate control ability with an acceptable gate break-down voltage and become an alternative choice in the design of the gate structure for Ga2O3 MOSFETs. (C) 2018 Author(s).