(Invited) Frequency Dispersion and Band Alignments in ZrO2/n-GaAs MOS Capacitor

Compound III-V semiconductors such as GaAs have the potential to replace Si as the channel material in metal-oxide-semiconductor-field-effect-transistors (MOSFET) due to their high electron mobility. However, it is extremely important to remove native oxide from the surface of GaAs. GaAs surfaces were self-cleaned through fast pulsing of the Trimethylaluminum (TMA) precursor by reducing and restraining the regrowth of native oxides using the atomic layer deposition (ALD). The thermal conversion of As-O in to Ga-O reduction was evaluated by the x-ray photoelectron spectroscopy. Metal oxide semiconductor (MOS) capacitor was using ZrO₂ as high-k gate dielectric on n-GaAs substrates, and their superior performance in electrical properties has been demonstrated. ZrO₂/GaAs capacitor exhibits superior capacitance-voltage characteristics reduced leakage current due to reduced interfacial trap density. These studies have remarkable significance for the development of high-throughput innovative electronics, using ZrO₂ as high-k dielectric.

The interfacial characteristics and band alignments of high-k ZrO₂ on n-GaAs have been investigated by experimentally and density functional theory. We have demonstrated that the frequency dispersion due to interface traps in capacitance-voltage characteristics of ZrO₂/GaAs interface was significantly reduced through self-cleaning by trimethylalumina. The experimental valence band offset of 2.10 eV from X-ray photoelectron spectroscopy is found to be lower than that of the calculated value of 3.02 eV. The calculated conduction band offset is 1.21 eV compared to the experimental value of 1.38 eV confirms significant reduction of interface traps due to the Fermi-level pinning minimizing band misalignment.