Sputter-deposited La ₂O ₃ on p-GaAs for gate dielectric applications

The interfacial and electrical properties of RF sputtered La ₂O ₃ on p-GaAs substrates with and without ultrathin Si interface passivation layer (IPL) are reported. X-ray photoelectron spectroscopy (XPS) studies revealed the formation of thermally stable interfacial native oxide (Ga-oxide and As-oxide) for La ₂O ₃Sip-GaAs gate stacks. The presence of (La ₂O ₃) _1-x(SiO ₂) _x at the interface prevented the formation of La-hydroxide which improved the metal-oxide-semiconductor (MOS) device characteristics, such as interface state density (∼1.2 × 10 ¹²eV ^-1cm ^-2), frequency dispersion (∼7), and hysteresis voltage (∼260 mV). A gate leakage current density of 1.1 × 10 ^-5 A.cm ^-2 has been achieved at V _fb-1 V for an equivalent oxide thickness of 3.4 nm and small flat-band voltage instability under constant voltage stressing was observed. The electrical properties of AlLa ₂O ₃Sip-GaAs MOS capacitors were found to improve after post deposition annealing at 500°C.