Atomic Layer Deposition of $\hbox{SiO}_{2}$ for AlGaN/GaN MOS-HFETs

This letter investigates the electrical properties of SiO
₂
gate dielectric on GaN heterostructures deposited by atomic layer deposition (ALD). ALD SiO
₂
has a dielectric constant of 3.9 and a bandgap of 8.8 eV. ALD SiO
₂
provides a good interface to GaN and minimizes the interfacial layer growth. The threshold voltage of metal-oxide-semiconductor heterojunction field-effect transistors with ALD SiO
₂
dielectric is -1.5 V, owing to a fixed charge concentration of -1.6 × 10
¹²
cm
^-2
. It was also found that devices with ALD SiO
₂
dielectric exhibit three orders of magnitude reduction in gate leakage current compared to conventional Schottky gate HFETs.