Al2O3/ β -Ga2O3(-201) Interface Improvement Through Piranha Pretreatment and Postdeposition Annealing

In this letter, we report on the improvement of atomic layer deposited (ALD) Al 2 O 3 / <tex-math notation="LaTeX">β </tex-math> –Ga 2 O 3 (-201) interface quality through piranha pretreatment and postdeposition annealing (PDA). The high quality interface is verified via the temperature dependent capacitance–voltage ( <tex-math notation="LaTeX">C </tex-math> – <tex-math notation="LaTeX">V </tex-math> ) and photo-assisted (deep UV) <tex-math notation="LaTeX">C </tex-math> – <tex-math notation="LaTeX">V </tex-math> measurements, considering its ultra wide bandgap of 4.8 eV for <tex-math notation="LaTeX">β </tex-math> -Ga 2 O 3 . A low <tex-math notation="LaTeX">C </tex-math> – <tex-math notation="LaTeX">V </tex-math> hysteresis of 0.1 V from the measurement frequency of 1 kHz to 1 MHz is obtained, compared with the hysteresis of 0.45 V without piranha optimization. An average interface trap density <tex-math notation="LaTeX">( Dᵢₜ) </tex-math> of <tex-math notation="LaTeX">2.3 × 10¹¹ </tex-math> cm <tex-math notation="LaTeX">⁻²· </tex-math> eV <tex-math notation="LaTeX">⁻¹ </tex-math> is extracted from the photo <tex-math notation="LaTeX">C </tex-math> – <tex-math notation="LaTeX">V </tex-math> measurements. Piranha pretreatments and PDA turn out to be an effective way to improve the ALD Al 2 O 3 / <tex-math notation="LaTeX">β </tex-math> –Ga 2 O 3 (-201) interface for future high quality Ga 2 O 3 metal–oxide–semiconductor field-effect transistors.