Interface State Density of Atomic Layer Deposited Al2O3 on Beta-Ga2O3

Abstract In this study, an atomic layer deposited (ALD) Al 2 O 3 with a thickness of 40 nm was used as a dielectric layer for gallium oxide (Ga 2 O 3 ) metal-oxide-semiconductor (MOS) capacitors. Interface state ( D it ) of 1.6×10 12 cm -2 /eV was extracted at 0.7 eV from conduction band ( E C ). Introduction β -Ga 2 O 3 is a promising candidate for power device applications due to its wide bandgap of 4.7–4.9 eV with a breakdown electric field 8 MV/cm, which is about three times larger than those of SiC and GaN power device materials. Along with the reports on high voltage Schottky diodes, MOS transistors have now been reported. In this research, ALD-Al 2 O 3 with a thickness of 40 nm has been used as a gate dielectric and its interface properties are investigated. Experiment A 40-nm-thick-Al 2 O 3 gate dielectric film was deposited by ALD on the surface of a Ga 2 O 3 substrate with n-type epitaxial layer. The doping density ( N d ) of the epitaxial layer was 2.3×10 16 cm -3 . The samples were transferred to a sputter chamber and 50-nm-thick W film followed by 50-nm-thick TiN was deposited by RF magnetron sputtering as a gate electrode. The capacitor was patterned by reactive ion etching (RIE) to form gate electrodes. Finally, a 10-nm-thick Ti followed by a 50-nm-thick TiN was deposited on the backside of the substrate as an Ohmic contact. Figure 1 shows the schematic illustration of the fabricated MOS capacitor. Results Capacitance-voltage ( C - V ) curves measured from 1 kHz to 100 kHz are shows in fig.2. The equivalent oxide thickness (EOT) of the dielectric layer was 18.3 nm. The D it of the capacitor was evaluated by conductance method. Figure 3 shows the extracted D it distribution in the bandgap of Ga 2 O 3 , where a 1.6×10 12 cm -2 /eV was obtained at 0.7 eV from E C . Conclusion Interface property of Al 2 O 3 / β -Ga2O3 was evaluated by conductance method. A 1.6×10 12 cm -2 /eV was obtained at 0.7 eV from E C . References [1] M. Higashiwaki et al., Appl. Phys. Lett, 103 , 123511 (2013) [2] K. Zeng, Y. Jia, and U. Singisetti, IEEE Electron Device Lett. 37, 906 (2016) Figure 1