Bulk and interface trapping in the gate dielectric of GaN based metal-oxide-semiconductor high-electron-mobility transistors

The trapping phenomena in GaN metal-oxide-semiconductor high-electron mobility transistor structures with 10 and 20-nm thick Al₂O₃ gate dielectric grown by metal-organic chemical vapor deposition were deeply investigated using comprehensive capacitance-voltage measurements. By controlling the interface traps population, substantial electron trapping in the dielectric bulk was identified. Separation between the trapping process and the interface traps emission allowed us to determine distribution of interface trap density in a wide energy range. Temperature dependence of the trapping process indicates thermionic field emission of electrons from the gate into traps with a sheet density of ∼10¹³ cm⁻², located a few nm below the gate.