Low interface state density and low leakage current of atomic‐layer deposited TiO 2 /Al 2 O 3 /sulfur‐treated GaAs

The (NH 4 ) 2 S treatment can reduce native oxides and passivate GaAs. Atomic‐layer‐deposited (ALD‐Al 2 O 3 ) can further remove the residue native oxides by self‐cleaning. For the first time, native oxides can be sufficiently removed by the combination of (NH 4 ) 2 S treatment and ALD‐Al 2 O 3 . Stacked with high dielectric constant TiO 2 prepared by atomic‐layer deposition on a Al 2 O 3 /(NH 4 ) 2 S‐treated GaAs MOS capacitor, the leakage current densities can reach 1.9 × 10 −8 and 3.1 × 10 −6  A/cm 2 at ±2 MV/cm. The dielectric constant is 25 and the interface state density is about 2.4 × 10 11  cm −2  eV −1 .