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/ $\beta $ -gallium oxide ( $\beta $ -Ga2O3) metal-insulator–semiconductor (MIS) Schottky barrier diode (SBD) with low turn-on voltage ( ${V}_{\text {on}}$ ) and reverse leakage current. By employing an ultrathin AlN layer enabled by atomic layer deposition (ALD), the resulting AlN/ $\beta $ -Ga2O3 MIS SBD exhibits a remarkably low leakage current of $0.1~\mu $ A/cm2, which is three orders of magnitude smaller than that of the conventional $\beta $ -Ga2O3 SBD. Meanwhile, the AlN/ $\beta $ -Ga2O3 MIS SBD shows a significantly improved breakdown voltage from 208 V up to 890 V, while maintaining a relatively low ${V}_{\text {on}}$ of 0.92 V and on-resistance ( ${R}_{\text {on}}$ ) of 11.8 m $\Omega \cdot $ 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/ $\beta $ -Ga2O3 heterojunction with a large conduction band offset ( $\Delta {E}_{C}$ ) 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 $\beta $ -Ga2O3 SBDs and the AlN/ $\beta $ -Ga2O3 SBDs with state-of-art performances open up more opportunities in future power electronics.