Work-function difference between Al and n-GaN from Al-gated n-GaN∕nitrided-thin-Ga2O3∕SiO2 metal oxide semiconductor structures

Abstract

In most previous reports on Al-gated n-GaN∕SiO2 metal–oxide–semiconductor (MOS) structures, the work–function difference between Al and n-GaN (ϕms) has been chosen as 0V by assuming that the work function of the Al gate and n-GaN are both 4.1eV. In this letter, ϕms is determined as ∼0.1V using Al-gated n-GaN∕nitrided-thin-Ga2O3∕SiO2 MOS capacitors by measuring flatband voltage as a function of oxide thickness. Formation of an ultrathin (∼0.6-nm-thick) Ga2O3 layer on n-GaN prior to the deposition of SiO2 is important to prevent uncontrolled parasitic oxidation of then-GaN surface and possibly reduces the interface dipole between n-GaN and SiO2.