D. M. Zhernokletov

Accumulation capacitance frequency dispersion of III-V metal-insulator-semiconductor devices due to disorder induced gap states

The origin of the anomalous frequency dispersion in accumulation capacitance of metal-insulator-semiconductor devices on InGaAs and InP substrates is investigated using modeling, electrical characterization, and chemical characterization. A comparison of the border trap model and the disorder induced gap state model for frequency dispersion is performed. The fitting of both models to experimental data indicate that the defects responsible for the measured dispersion are within approximately 0.8 nm of the surface of the crystalline semiconductor. The correlation between the spectroscopically detected bonding states at the dielectric/III-V interface, the interfacial defect density determined using capacitance-voltage, and modeled capacitance-voltage response strongly suggests that these defects are associated with the disruption of the III-V atomic bonding and not border traps associated with bonding defects within the high-k dielectric.

Effect of post deposition anneal on the characteristics of HfO2/InP metal-oxide-semiconductor capacitors

The interface trap density (Dit) and bonding of the HfO2/InP interface is investigated. The energy distribution of interface states extracted using capacitance-voltage measurements show a peak near midgap in InP and a tail, which extends into the InP conduction band. Both the Dit peak and the conduction band Dit increase with increasing post-deposition annealing temperature. A substantial increase in the native oxides with annealing temperature is observed with x-ray photoelectron spectroscopy. The possible bonding states responsible for the defects are presented.

Epitaxial integration of ferromagnetic correlated oxide LaCoO3 with Si (100)

We have grown epitaxial strained LaCoO3 on (100)-oriented silicon by molecular beam epitaxy using a relaxed epitaxial SrTiO3 buffer layer. Superconducting quantum interference device magnetization measurements show that, unlike the bulk material, the ground state of the strained LaCoO3 on silicon is ferromagnetic with a TC of 85 K. First principles calculations suggest that a ferromagnetic ground state can be stabilized in LaCoO3 by a sufficiently large biaxial tensile strain with the transition accompanied by a partial untilting of the CoO6 octahedra.

Interfacial oxide re-growth in thin film metal oxide III-V semiconductor systems

The Al2O3/GaAs and HfO2/GaAs interfaces after atomic layer deposition are studied using in situ monochromatic x-ray photoelectron spectroscopy. Samples are deliberately exposed to atmospheric conditions and interfacial oxide re-growth is observed. The extent of this re-growth is found to depend on the dielectric material and the exposure temperature. Comparisons with previous studies show that ex situ characterization can result in misleading conclusions about the interface reactions occurring during the metal oxide deposition process.

Electrical and chemical characteristics of Al2O3/InP metal-oxide-semiconductor capacitors

The interface trap density (Dit) and bonding at the Al2O3/InP interface was investigated using capacitance-voltage (C-V) measurements and X-ray photoelectron spectroscopy (XPS). The Dit extracted using C-V measurements show a peak near midgap and a tail, which extends into the InP conduction band. After post high-k deposition annealing, only midgap Dit increases while minimal change in conduction band Dit is observed. The magnitude of extracted Dit is higher for the Al2O3/InP interface compared to the HfO2/InP interface. XPS analysis shows that the native oxides at the Al2O3/InP interface are more phosphorous rich than for HfO2/InP interface.

In situ surface pre-treatment study of GaAs and In0.53Ga0.47As

The impact of using multiple cycles of trimethyl-aluminum (TMA) prior to Al2O3 deposition on the properties of (NH4)2S treated In0.53Ga0.47As and GaAs substrates was investigated by in situ x-ray photoelectron spectroscopy. Increasing the number of TMA cycles prior to Al2O3 atomic layer deposition (ALD) was seen to decrease the concentration of As-As detected at the oxide-semiconductor interface. The impact of annealing the (NH4)2S treated GaAs surface in situ prior to ALD, in various environments, was also investigated.

Indium diffusion through high-k dielectrics in high-k/InP stacks

Evidence of indium diffusion through high-k dielectric (Al2O3 and HfO2) films grown on InP (100) by atomic layer deposition is observed by angle resolved X-ray photoelectron spectroscopy and low energy ion scattering spectroscopy. The analysis establishes that In-out diffusion occurs and results in the formation of a POx rich interface.

Surface and interfacial reaction study of half cycle atomic layer deposited HfO2 on chemically treated GaSb surfaces

An in situ half-cycle atomic layer deposition/X-ray photoelectron spectroscopy (XPS) study was conducted in order to investigate the evolution of the HfO2 dielectric interface with GaSb(100) surfaces after sulfur passivation and HCl etching, designed to remove the native oxides. With the first pulses of tetrakis(dimethylamido)hafnium(IV) and water, a decrease in the concentration of antimony oxide states present on the HCl-etched surface is observed, while antimony sulfur states diminished below the XPS detection limit on sulfur passivated surface. An increase in the amount of gallium oxide/sulfide is seen, suggesting oxygen or sulfur transfers from antimony to gallium during antimony oxides/sulfides decomposition.

Optimization of the ammonium sulfide (NH4)2S passivation process on InSb(111)A

The passivation of the InSb semiconductor surface and related alloys is of interest due to their small bandgaps and high bulk mobilities, which make them favorable materials for use in quantum-well transistors and long wavelength optoelectronic devices. One of the most common passivation approaches is an ammonium sulfide ((NH4)2S) treatment; however, there are variations in the reported processing conditions for this procedure. This study represents a broad review of the different sulfur treatment parameters used as well as determining the optimal processing parameters in terms of length of time the sample is in the solution and the (NH4)2S concentration, by measuring the level of the residual native oxides, and surface roughness, by means of x-ray photoelectron spectroscopy and atomic force microscopy, respectively.

In situ study of HfO2 atomic layer deposition on InP(100)

The interfacial chemistry of the native oxide and chemically treated InP samples during atomic layer deposition (ALD) HfO2 growth at 250  °C has been studied by in situ X-ray photoelectron spectroscopy. The In-oxide concentration is seen to gradually decrease on the native oxide and acid etched samples. No significant changes of the P-oxide concentrations are detected, while the P-oxides chemical states are seen to change gradually during the initial cycles of ALD on the native oxide and the chemically treated samples. (NH4)2S treatment strongly decreases In-oxide and P-oxide concentrations prior to ALD and maintains low concentrations during the ALD process.