Low Turn-On Voltage and Reverse Leakage Current β -Ga₂O₃ MIS Schottky Barrier Diodes With an AlN Interfacial Layer

We demonstrate for the first time a vertical metal/AlN/<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula>-gallium oxide (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula>-Ga2O3) metal-insulator–semiconductor (MIS) Schottky barrier diode (SBD) with low turn-on voltage (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{\text {on}}$ </tex-math></inline-formula>) and reverse leakage current. By employing an ultrathin AlN layer enabled by atomic layer deposition (ALD), the resulting AlN/<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula>-Ga2O3 MIS SBD exhibits a remarkably low leakage current of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.1~\mu $ </tex-math></inline-formula>A/cm2, which is three orders of magnitude smaller than that of the conventional <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula>-Ga2O3 SBD. Meanwhile, the AlN/<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula>-Ga2O3 MIS SBD shows a significantly improved breakdown voltage from 208 V up to 890 V, while maintaining a relatively low <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{\text {on}}$ </tex-math></inline-formula> of 0.92 V and <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small>-resistance (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${R}_{\text {on}}$ </tex-math></inline-formula>) of 11.8 m<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega \cdot $ </tex-math></inline-formula>cm2, respectively. I–V measurements conducted across a range of temperatures from 298 to 432 K indicate that thermionic field emission (TFE) and trap-assisted tunneling (TAT) are the predominant electron transport mechanisms under forward bias if inserting 2 nm AlN, while TFE becomes dominant mechanism when the AlN thickness increases up to 5 nm. X-ray photoelectron spectroscopy (XPS) characterizations reveal the type I alignment for AlN/<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula>-Ga2O3 heterojunction with a large conduction band offset (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta {E}_{C}$ </tex-math></inline-formula>) of 1 eV, which could function as an electron transport barrier under reverse conditions, thereby greatly suppressing the leakage current. Our study for the first time suggests a great potential for ALD-derived AlN films to be an interfacial layer in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula>-Ga2O3 SBDs and the AlN/<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula>-Ga2O3 SBDs with state-of-art performances open up more opportunities in future power electronics.