Polycrystalline/Amorphous HfO2Bilayer Structure as a Gate Dielectric for β-Ga2O3MOS Capacitors

초록

We report the comparison of the atomic layer deposited polycrystalline (p-)/amorphous (a-) HfO2 bilayer gate dielectric with p-HfO2/a-Al2O3 for enhanced β-Ga2O3 metal oxide semiconductor capacitors (MOSCAPs). A discrepancy in the temperature-dependent hysteretic behaviors is observed, and thus, pulse capacitance-voltage (C-V) measurements are employed to investigate interface properties at the border between the amorphous (Al2O3 or HfO2) and polycrystalline (HfO2) oxide layers. The proposed p-HfO2/a-HfO2 exhibits similar interface trap densities (Dit) at the interface between the bilayer dielectric and β-Ga2O3, and shows lower border trap density (Nbt). An effective barrier height of 1.62 eV for the p-HfO2/a-HfO2 with a breakdown field of 9.1 MV/cm, which is higher than 1.01 eV of p-HfO2/a-Al2O3, is obtained from the current density-voltage (J-V) characteristics using the Folwer-Nordheim model. Moreover, as compared with a p-HfO2 single layer, the additional a-HfO2 layer on top of p-HfO2 is beneficial to improve hysteretic and leakage characteristics, while maintaining its high-quality interface. The p-HfO2/a-HfO2 bilayer with improved interface properties as well as a large positive flat-band voltage of 4.7 V is a promising candidate for the metal/high-k stack of β-Ga2O3 MOSCAPs. © 1963-2012 IEEE.

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