Band offset measurements of the Si3N4/GaN (0001) interface

Abstract

X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy were used to measure electronic states as ${\mathrm{Si}}_3{\mathrm{N}}_4$ was deposited on clean GaN (0001) surfaces. The n-type ${\text{(2×10}}^{18})$ and p-type ${\text{(1×10}}^{17})$ GaN surfaces were atomically cleaned in ${\mathrm{NH}}_3$ at 860 °C, and the n-and p-type surfaces showed upward band bending of $\text{∼0.2±0.1\hspace{0.17em}}\mathrm{eV}$ and downward band bending of $\text{1.1±0.1\hspace{0.17em}}\mathrm{eV},$ respectively, both with an electron affinity of $\text{3.1±0.1\hspace{0.17em}}\mathrm{eV}.$ Layers of Si (∼0.2 nm) were deposited on the clean GaN and nitrided using an electron cyclotron resonance ${\mathrm{N}}_2$ plasma at 300 °C and subsequently annealed at 650 °C for densification into a ${\mathrm{Si}}_3{\mathrm{N}}_4$ film. Surface analysis was performed after each step in the process, and yielded a valence band offset of $\text{0.5±0.1\hspace{0.17em}}\mathrm{eV}.$ Both interfaces exhibited type II band alignment where the valence band maximum of GaN lies below that of the ${\mathrm{Si}}_3{\mathrm{N}}_4$ valence band. The conduction band offset was deduced to be $\text{2.4±0.1\hspace{0.17em}}\mathrm{eV},$ and a change of the interface dipole of $\text{1.1±0.1\hspace{0.17em}}\mathrm{eV}$ was observed for ${\mathrm{Si}}_3{\mathrm{N}}_4/\mathrm{GaN}$ interface formation.