Sputter-Deposited La₂O₃on p-GaAs for Gate Dielectric Applications

Abstract

The interfacial and electrical properties of RF sputtered La2O3 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 La2O3/Si/p-GaAs gate stacks. The presence of (La2O3)1-x(SiO2)x at the interface prevented the formation of La-hydroxide which improved the metal-oxide-semiconductor (MOS) device characteristics, such as interface state density (∼1.2×1012eV−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 Vfb-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 Al/La2O3/Si/p-GaAs MOS capacitors were found to improve after post deposition annealing at 500°C.