Browsing by Author "Vogel, E. M."
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Item Accumulation Capacitance Frequency Dispersion of Ⅲ-Ⅴ Metal-Insulator-Semiconductor Devices due to Disorder Induced Gap States(American Institute of Physics Inc., 2014-07-07) Galatage, R. V.; Zhernokletov, Dmitry M.; Dong, Hong; Brennan, Barry; Hinkle, Christopher L.; Wallace, Robert M.; Vogel, E. M.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 0.8nm 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.Item Chemical and Electrical Characterization of the HfO2/InAlAs InterfaceBrennan, Barry; Galatage, Rohit V.; Thomas, K.; Pelucchi, E.; Hurley, P. K.; Kim, Jiyoung; Hinkle, Christopher L.; Vogel, E. M.; Wallace, Robert M.InAlAs has the potential to be used as a barrier layer in buried channel quantum well field effect transistor devices due to favorable lattice-matching and carrier confinement properties with InGaAs. Field effect device structures of this nature may also require a high-k oxide deposited on the InAlAs surface to reduce leakage current. This study investigates the impact of surface preparations and atomic layer deposition of HfO2 on these surfaces using x-ray photoelectron spectroscopy to analyse the chemical interactions taking place, as well as the electrical performance of associated capacitor devices. A large concentration of As related surface features is observed at the InAlAs surface, and is attributed to a large Dit response in electrical measurements.Item Cleaning Graphene with a Titanium Sacrificial LayerJoiner, C. A.; Roy, T.; Hesabi, Z. R.; Chakrabarti, B.; Vogel, E. M.Graphene is a promising material for future electronic applications and chemical vapor deposition of graphene on copper is a promising method for synthesizing graphene on the wafer scale. The processing of such graphene films into electronic devices introduces a variety of contaminants which can be difficult to remove. An approach to cleaning residues from the graphene channel is presented in which a thin layer of titanium is deposited via thermal e-beam evaporation and immediately removed. This procedure does not damage the graphene as evidenced by Raman spectroscopy, greatly enhances the electrical performance of the fabricated graphene field effect transistors, and completely removes the chemical residues from the surface of the graphene channel as evidenced by x-ray photoelectron spectroscopy.Item Tunneling Characteristics in Chemical Vapor Deposited Graphene-Hexagonal Boron Nitride-Graphene Junctions(Amer Inst Physics) Roy, T.; Liu, L.; de la Barrera, S.; Chakrabarti, B.; Hesabi, Z. R.; Joiner, C. A.; Feenstra, R. M.; Gu, G.; Vogel, E. M.Large area chemical vapor deposited graphene and hexagonal boron nitride was used to fabricate graphene-hexagonal boron nitride-graphene symmetric field effect transistors. Gate control of the tunneling characteristics is observed similar to previously reported results for exfoliated graphene-hexagonal boron nitride-graphene devices. Density-of-states features are observed in the tunneling characteristics of the devices, although without large resonant peaks that would arise from lateral momentum conservation. The lack of distinct resonant behavior is attributed to disorder in the devices, and a possible source of the disorder is discussed.