Improvement of Atomic-Layer-Deposited Al2O3/GaAs Interface Property by Sulfuration and NH3 Thermal Nitridation

Fermi level pinning at the interface between high-k gate dielectric and GaAs induced by unstable native oxides is a major obstacle for high performance GaAs-based metal-oxide-semiconductor (MOS) devices. We demonstrate the improved Al2O3/GaAs interfacial characteristics by (NH4)2S immersion and NH3 thermal pretreatment prior to Al2O3 deposition. X-ray photoelectron spectroscopy (XPS) analysis confirms that sulfuration of GaAs surface by (NH4)2S solution can effectively reduce As-O bonds while Ga-O bonds and elemental As still exist at Al2O3/GaAs interface. However, it is found that N incorporation during the further thermal nitridation on sulfurated GaAs can effectively suppress the native oxides and elemental As in the sequent deposition of Al2O3. Atomic force microscopy (AFM) shows that the further thermal nitridation on sulfurated GaAs surface can also improve the surface roughness.