Interface control and modification of band alignment and electrical properties of HfTiO/GaAs gate stacks by nitrogen incorporation

Author(s): Gang He ¹ ^, ² ^, ³ ^, ⁴ ^, ⁵ , Jiangwei Liu ⁶ ^, ⁷ ^, ⁸ , Hanshuang Chen ¹ ^, ² ^, ³ ^, ⁴ , Yanmei Liu ¹ ^, ² ^, ³ ^, ⁴ , Zhaoqi Sun ¹ ^, ² ^, ³ ^, ⁴ , Xiaoshuang Chen ⁵ ^, ⁹ ^, ¹⁰ ^, ¹¹ , Mao Liu ¹² ^, ¹³ ^, ¹⁴ ^, ⁹ ^, ¹¹ , Lide Zhang ¹² ^, ¹³ ^, ¹⁴ ^, ⁹ ^, ¹¹

Publication date (Electronic): 2014

Journal: J. Mater. Chem. C

Publisher: Royal Society of Chemistry (RSC)

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Abstract

Effects of nitrogen incorporation on the interface chemical bonding states, optical dielectric function, band alignment, and electrical properties of sputtering-derived HfTiO high- kgate dielectrics on GaAs substrates have been studied by angle resolved X-ray photoemission spectroscopy (ARXPS), spectroscopy ellipsometry (SE), and electrical measurements. XPS analysis has confirmed that the interfacial layer of a HfTiO/GaAs gate stack is suppressed effectively after nitrogen incorporation. Analysis by SE has confirmed that reduction in band gap and increase in refractive index are observed with the incorporation of nitrogen. Reduction in valence band offset and increase in conduction band offset have been observed for a HfTiON/GaAs gate stack. Electrical measurements based on metal-oxide-semiconductor (MOS) capacitors have shown that the MOS capacitor with a HfTiON/GaAs stacked gate dielectric annealed at 600 °C exhibits low interface-state density (2.8 × 10 ¹²cm ⁻²eV ⁻¹), small gate leakage current (2.67 × 10 ⁻⁵A cm ⁻²at V _g= V _fb+ V), and large dielectric constant (25.8). The involved mechanisms may originate from the decrease in the interface state density and the increase in the conduction band offset. The appropriate band offset relative to GaAs and excellent interface properties render HfTiON/GaAs as promising gate stacks in future III–V-based devices.

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N-Doped Graphene-SnO2 Sandwich Paper for High-Performance Lithium-Ion Batteries

Xinqiang Cao, Laure Bourgeois, Hasigaowa Guan … (2012)

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Atomistic origins of high rate capability and capacity of N-doped graphene for lithium storage.

Xi WANG, Qunhong Weng, Xizheng Liu … (2014)

Distinct from pure graphene, N-doped graphene (GN) has been found to possess high rate capability and capacity for lithium storage. However, there has still been a lack of direct experimental evidence and fundamental understanding of the storage mechanisms at the atomic scale, which may shed a new light on the reasons of the ultrafast lithium storage property and high capacity for GN. Here we report on the atomistic insights of the GN energy storage as revealed by in situ transmission electron microscopy (TEM). The lithiation process on edges and basal planes is directly visualized, the pyrrolic N "hole" defect and the perturbed solid-electrolyte-interface configurations are observed, and charge transfer states for three N-existing forms are also investigated. In situ high-resolution TEM experiments together with theoretical calculations provide a solid evidence that enlarged edge {0002} spacings and surface hole defects result in improved surface capacitive effects and thus high rate capability and the high capacity are owing to short-distance orderings at the edges during discharging and numerous surface defects; the phenomena cannot be understood previously by standard electron or X-ray diffraction analyses.