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Defects at the interface between InAs and a native or high permittivity oxide layer are one of the main challenges for realizing III-V semiconductor based metal oxide semiconductor structures with superior device performance. Here we passivate the InAs(100) substrate by removing the native oxide via annealing in ultra-high vacuum (UHV) under a flux of atomic hydrogen and growing a stoichiometry controlled oxide (thermal oxide) in UHV, prior to atomic layer deposition (ALD) of an Al2O3 high-k layer. The semiconductor-oxide interfacial stoichiometry and surface morphology are investigated by synchrotron based X-ray photoemission spectroscopy, scanning tunneling microscopy, and low energy electron diffraction. After thermal oxide growth, we find a thin non-crystalline layer with a flat surface structure. Importantly, the InAs-oxide interface shows a significantly decreased amount of In3+, As5+, and As0 components, which can be correlated to electrically detrimental defects. Capacitance-voltage measurements confirm a decrease of the interface trap density in gate stacks including the thermal oxide as compared to reference samples. This makes the concept of a thermal oxide layer prior to ALD promising for improving device performance if this thermal oxide layer can be stabilized upon exposure to ambient air. [ABSTRACT FROM AUTHOR]

Atomic layer deposition (ALD) enables the ultrathin high-quality oxide layers that are central to all modern metal-oxide-semiconductor circuits. Crucial to achieving superior device performance are the chemical reactions during the first deposition cycle, which could ultimately result in atomic-scale perfection of the semiconductor–oxide interface. Here, we directly observe the chemical reactions at the surface during the first cycle of hafnium dioxide deposition on indium arsenide under realistic synthesis conditions using photoelectron spectroscopy. We find that the widely used ligand exchange model of the ALD process for the removal of native oxide on the semiconductor and the simultaneous formation of the first hafnium dioxide layer must be significantly revised. Our study provides substantial evidence that the efficiency of the self-cleaning process and the quality of the resulting semiconductor–oxide interface can be controlled by the molecular adsorption process of the ALD precursors, rather than the subsequent oxide formation. [ABSTRACT FROM AUTHOR]

The Half Heuslers are currently an attractive family of compounds for high temperature thermoelectrics research, and recently, there has been renewed interest since some of these compounds are proposed to be topological insulators. NiTiSn belongs to the family of 18 valence electron Half Heuslers that are predicted to be semiconducting, despite being composed entirely of metallic elements. The growth of the Half Heusler compound NiTiSn by molecular beam epitaxy is demonstrated. The NiTiSn films are epitaxial and single crystalline as observed by reflection high-energy electron diffraction and x-ray diffraction. Temperature dependent transport measurements suggest the films may be semiconducting, but with a high background carrier density indicative of a high density of electrically active defect states. Methods of protecting the sample surface for synchrotron-based photoemission measurements are explored. These methods may be applied to the study of surface electronic structure in unconventional materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hydrogen plasma treatment in ultra-high vacuum removes native oxide from GaSb. • GaSb nanowire surfaces are easier to clean than the planar GaSb substrates. • Hydrogen plasma treatment prior to high-k ALD improves interface quality. • Commercial ALD chambers require cleaner environment to avoid GaSb re-oxidation. Due to its high hole-mobility, GaSb is a highly promising candidate for high-speed p-channels in electronic devices. However, GaSb exhibits a comparably thick native oxide causing detrimental interface defects, which has been proven difficult to remove. Here we present full oxide removal from GaSb surfaces using effective hydrogen plasma cleaning, studied in-situ by synchrotron-based X-ray photoelectron spectroscopy under ultrahigh vacuum (UHV). GaSb nanowires turn out to be cleaned faster and more efficiently than planar substrates. Since the UHV conditions are not scalable for industrial sample processing, H-plasma cleaning is furthermore used as pre-treatment prior to atomic layer deposition (ALD) of a protective high-k layer to demonstrate the use of the cleaning step in a more realistic fabrication situation. We observe a cleaning effect of the H-plasma even in the ALD environment, but we also find residual Ga- and Sb-oxides at the GaSb-high-k interface, which we attribute to re-oxidation of the cleaned surface. Our results indicate that an improved control of the ALD reactor vacuum environment could realize oxide- and defect-free interfaces in GaSb-based electronics. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two OxRRAM stacks -TiN bottom metal electrode were fabricated by PVD and ALD. • The HfO x layer in HfO x /PVD-TiN is found to be more oxygen deficient. • Higher oxygen deficiency leads to larger band bending at HfO x /PVD-TiN interface. • Higher oxygen deficiency results in a higher Schottky barrier at the interface. • ALD-TiN O xRRAM shows low voltage switching - 106 switches with 10 μA ± 1.0 V pulses. Resistive random access memory (RRAM) technologies based on non-volatile resistive filament redox switching oxides have the potential of drastically improving the performance of future mass-storage solutions. However, the physico-chemical properties of the TiN bottom metal electrode (BME) can significantly alter the resistive switching (RS) behavior of the oxygen-vacancy RRAM devices, yet the correlation between RS and the physico-chemical properties of TiN and HfO x /TiN interface remains unclear. Here, we establish this particular correlation via detailed material and electrical characterization for the purpose of achieving further performance enhancement of the stack integration. Two types of RRAM stacks were fabricated where the TiN BME was fabricated by physical vapor deposition (PVD) and atomic layer deposition (ALD), respectively. The HfO x layer in HfO x /PVD-TiN is more oxygen deficient than that of the HfO x /ALD-TiN because of more defective PVD-TiN and probably because pristine ALD-TiN has a thicker TiO 2 overlayer. Higher concentration of oxygen vacancies induces a larger magnitude of band bending at the HfO x /PVD-TiN interface and leads to the formation of a higher Schottky barrier. Pulsed endurance measurements of up to 106 switches, with 10 μA ± 1.0 V pulses, demonstrate the potential of the studied ultra-thin-HfO x /TiN device stack for dense, large scale, and low-power memory integration. [ABSTRACT FROM AUTHOR]