Leakage current conduction mechanisms and electrical properties of atomic-layer-deposited HfO 2 /Ga 2 O 3 MOS capacitors

In this paper, current conduction mechanisms in HfO 2 / β -Ga 2 O 3 metal–oxide–semiconductor (MOS) capacitors under positive and negative biases are investigated using the current–voltage ( I – V ) measurements conducted at temperatures from 298 K to 378 K. The Schottky emission is dominant under positively biased electric fields of 0.37–2.19 MV cm −1 , and the extracted Schottky barrier height ranged from 0.88 eV to 0.91 eV at various temperatures. The Poole–Frenkel emission dominates under negatively biased fields of 1.92–4.83 MV cm −1 , and the trap energy levels are from 0.71 eV to 0.77 eV at various temperatures. The conduction band offset (Δ E c ) of HfO 2 / β -Ga 2 O 3 is extracted to be 1.31 ± 0.05 eV via x-ray photoelectron spectroscopy, while a large negative sheet charge density of 1.04 × 10 13 cm −2 is induced at the oxide layer and/or HfO 2 / β -Ga 2 O 3 interface. A low C – V hysteresis of 0.76 V, low interface state density ( D it ) close to 1 × 10 12 eV −1 cm −2 , and low leakage current density of 2.38 × 10 −5 A cm −2 at a gate voltage of 7 V has been obtained, suggesting the great electrical properties of HfO 2 / β -Ga 2 O 3 MOSCAP. According to the above analysis, ALD-HfO 2 is an attractive candidate for high voltage β -Ga 2 O 3 power devices.