Band Alignments of Atomic Layer Deposited ZrO₂and HfO₂High-k Dielectrics with (-201) β-Ga₂O₃

Abstract

The energy band alignment between atomic layer deposited (ALD) high-k dielectrics of ZrO2 and HfO2 with n-type β-Ga2O3 was evaluated using x-Ray photoelectron spectroscopy. The valence band offset was found to be −0.3 ± 0.04 eV and −0.5 ± 0.04 eV for ZrO2and HfO2, respectively, which produced type II, staggered gap alignments for both dielectrics with conduction band offsets greater than 1 eV. Capacitance-voltage measurements were conducted on metal-oxide-semiconductor (MOS) diodes and used to extract the dielectric constants (ɛ) of both oxides. ZrO2films had a nearly ideal ɛ of 24.7 (ɛ ∼ 25), while HfO2 exhibited a significantly lower ɛ of 14 (ɛ ∼ 25–30). These results, combined with the small hysteresis (≤0.09 eV) in the capacitance-voltage behavior for both films, is indicative of the high quality of these ALD oxides and their interface with the β-Ga2O3 making them potential candidates as gate dielectrics in power devices based on this relatively new ultra-wide bandgap material.