The reduction and removal of surface oxides from GaAs substrates by atomic layer deposition (ALD) of ${\mathrm{Al}}_2{\mathrm{O}}_3$ and $\mathrm{Hf}{\mathrm{O}}_2$ are studied using in situ monochromatic x-ray photoelectron spectroscopy. Using the combination of in situ deposition and analysis techniques, the interfacial “self-cleaning” is shown to be oxidation state dependent as well as metal organic precursor dependent. Thermodynamics, charge balance, and oxygen coordination drive the removal of certain species of surface oxides while allowing others to remain. These factors suggest proper selection of surface treatments and ALD precursors can result in selective interfacial bonding arrangements.

The method of surface preparation on $n$ -type GaAs, even with the presence of an amorphous-Si interfacial passivation layer, is shown to be a critical step in the removal of accumulation capacitance frequency dispersion. In situ deposition and analysis techniques were used to study different surface preparations, including $\mathrm{N}{\mathrm{H}}_4\mathrm{O}\mathrm{H}$ , Si-flux, and atomic hydrogen exposures, as well as Si passivation depositions prior to in situ atomic layer deposition of ${\mathrm{Al}}_2{\mathrm{O}}_3$ . As–O bonding was removed and a bond conversion process with Si deposition is observed. The accumulation capacitance frequency dispersion was removed only when a Si interlayer and a specific surface clean were combined.

Atomic H exposure of a GaAs surface at 390°C is a relatively simple method for removing the native oxides without altering the surface stoichiometry. In-situ reflection high energy electron diffraction and angle-resolved x-ray photoelectron spectroscopy have been used to show that this procedure applied to In0.2Ga0.8As effectively removes the native oxides resulting in an atomically clean surface. However, the bulk InGaAs stoichiometry is not preserved from this treatment. The In:Ga ratio from the substrate is found to decrease by 33%. The implications for high-mobility channel applications are discussed as the carrier mobility increases nearly linearly with the In content.

High dielectric constant hafnium oxide films were formed by electron beam (e-beam) evaporation on HF last terminated silicon (100) wafers. We report on the influence of low energy argon plasma $\left(\sim 70\text{eV}\right)$ and oxygen flow rate on the electrical, chemical, and structural properties of metal-insulator-silicon structures incorporating these e-beam deposited ${\text{HfO}}_2$ films. The use of the film-densifying low energy argon plasma during the deposition results in an increase in the equivalent oxide thickness (EOT) values. We employ high resolution transmission electron microscopy (HRTEM), x-ray photoelectron spectroscopy (XPS), and medium energy ion scattering experiments to investigate and understand the mechanisms leading to the EOT increase. We demonstrate very good agreement between the interfacial silicon oxide thicknesses derived independently from XPS and HRTEM measurements. We find that the e-beam evaporation technique enabled us to control the ${\text{SiO}}_x$ interfacial layer thickness down to $\sim 6\text{Å}$ . Very low leakage current density $\left(<{10}^{-4}\text{A}/{\text{cm}}^2\right)$ is measured at flatband voltage $+1\text{V}$ into accumulation for an estimated EOT of $10.9\pm 0.1\text{Å}$ . Based on a combined HRTEM and capacitance-voltage $\left(CV\right)$ analysis, employing a quantum-mechanical $CV$ fitting procedure, we determine the dielectric constant $\left(k\right)$ of ${\text{HfO}}_2$ films, and associated interfacial ${\text{SiO}}_x$ layers, formed under various processing conditions. The $k$ values are found to be 21.2 for ${\text{HfO}}_2$ and 6.3 for the thinnest $\left(\sim 6\text{Å}\right)$ ${\text{SiO}}_x$ interfacial layer. The cross-wafer variations in the physical and electrical properties of the ${\text{HfO}}_2$ films are presented.

A systematic capacitance-voltage study has been performed on GaAs metal-oxide-semiconductor (MOS) structures with atomic-layer-deposited $\mathrm{Hf}{\mathrm{O}}_2∕{\mathrm{Al}}_2{\mathrm{O}}_3$ nanolaminates as gate dielectrics. A $\mathrm{Hf}{\mathrm{O}}_2∕{\mathrm{Al}}_2{\mathrm{O}}_3$ nanolaminate gate dielectric improves the GaAs MOS characteristics such as dielectric constant, breakdown voltage, and frequency dispersion. A possible origin for the widely observed larger frequency dispersion on $n$ -type GaAs than $p$ -type GaAs is discussed. Further experiments show that the observed hysteresis is mainly from the mobile changes and traps induced by $\mathrm{Hf}{\mathrm{O}}_2$ in bulk oxide instead of those at oxide/GaAs interface.