Electronic structure and origin of intrinsic defects in sputtered HfTiO2 alloy dielectric on GaAs surface

In this work, we have investigated the electronic structure and electrical properties of sputter-deposited high-k dielectrics grown on p-GaAs substrate with post-deposition annealing at 500 °C/N2 ambient. Capacitance-voltage results show that co-sputtered amorphous-HfTiO2 alloy dielectric can reduce interfacial dangling bonds. HRTEM and AR- X-ray photoelectron spectroscopy results confirmed the formation of a thin interfacial layer during sputter deposition. At the atomistic level, the surface reaction and electronic interface structure were investigated by density-functional theory (DFT) calculations. Using the HSE functional, theoretical calculations of bulk HfO2, a-TiO2, and HfTiO2 band gaps are found to be 5.27, 2.61, and 4.03 eV, respectively. Consequently, in the HfTiO2/GaAs interface, the valance band offset is found to be reduced to 1.04 eV compared to HfO2/GaAs structure valance band offset of 1.45 eV. Reduction in border trap density (~1011 V/cm2) was observed due to Ti atoms bridging between As-dangling bonds. The angle-resolved XPS analysis further confirmed Ti-O-As chemical bonding with very thin (~20 Å) dielectric layers. •Electronic structure at the atomistic level of single and alloy dielectric/GaAs interface investigated.•Co-sputtered amorphous-HfTiO2 alloy dielectric reduces interface As-related dangling bonds.•Interface structure and surface reaction analyzed by HRTEM and Angle-resolved XPS.•density-functional theory (DFT) calculations for the bandgap and valence band offset of high-k/GaAs interface•Ti-atoms bridging between the As-dangling bonds studied and analyzed by ARXPS and electrical characterizations.