Improved high-field reliability for a SiC metal-oxide-semiconductor device by the incorporation of nitrogen into its HfTiO gate dielectric

Materials with high dielectric constant (k) have been used in SiC-based metal-oxide-semiconductor (MOS) devices to reduce the electric field in the gate dielectric and thus suppress a high-field reliability problem. In this work, high- k gate dielectrics Hfx Ti1-x O2 and Hfx Ti1-x ON are applied in SiC MOS devices and an ultrathin thermally grown SiO2 is used as an interlayer between SiC and the high- k materials to block electron injection from SiC into the low-barrier high- k materials. Incorporating nitrogen into the Hf-Ti oxide (by adding nitrogen gas during its sputtering) stacked with a SiO2 interlayer (Hfx Ti1-x O SiO2) results in a better gate dielectric for the MOS capacitor, such as smaller frequency dispersion in the capacitance-voltage curve, less oxide charges, and better interface quality. Moreover, the nitrogen incorporation increases the dielectric constant of the oxide, but causes higher dielectric leakage, which can be suppressed by the SiO2 interlayer. High-field stress under constant electric field is performed on the stacked/nonstacked Hf-Ti oxides and oxynitrides, and it turns out that the two oxynitrides show a much smaller flatband shift and a less stress-induced leakage current compared with the two oxides. Based on these results, the Hfx Ti1-x ON SiO2 stack could be a promising high- k gate dielectric for SiC MOS devices with enhanced reliability. © 2007 American Institute of Physics.published_or_final_versio

Effects of NO annealing and GaOxNy interlayer on GaN metal-insulator-semiconductor capacitor with SiO2 gate dielectric

SiO2 was deposited on GaN by radio-frequency sputtering to fabricate metal-insulator-semiconductor (MIS) capacitors. Before the deposition, an ultrathin GaOx Ny interlayer was thermally grown on the GaN wafer to improve the quality of the insulator/ GaN interface. The interface-trap density at 0.4 eV below the conduction bandedge was reduced by one order compared with that of a sample without the GaOx Ny interlayer. Annealing in NO gas at 800°C was conducted on both samples, and turned out to greatly suppress their oxide charges. The NO -annealed sample with the GaOx Ny interlayer achieved the lowest oxide-charge density of 1.7× 1011 cm-2, as compared to 9.5× 1011 cm-2 for its counterpart without the GaOx Ny interlayer and about 8.0× 1012 cm-2 for the two nonannealed samples. Moreover, the NO annealing was found to effectively reduce border traps. Secondary-ion mass spectrometry analysis was performed to explain how the GaOx Ny interlayer and NO annealing affect the performance of the GaN MIS capacitors. © 2007 The Electrochemical Society.published_or_final_versio

Behavioural insights into housing relocation decisions: The effects of the Beijing Olympics

This article examines the impact of mega events on Beijing housing market from a behavioural perspective. By exploring the situation surrounding the Beijing 2008 Summer Olympics, we analyse the relationship between mega-event regeneration and expected residential relocation outcomes. Our findings suggest that Beijing Olympic regeneration caused disadvantaged groups to anticipate relocation to undesirable areas, as a result of improved infrastructure, public security, and urban environment. Behavioural sciences research indicates that expectation influences decision-making by serving as a salient reference point. Agents who perceived themselves as in a disadvantaged position or holding a gloomy prospect of their future are more likely to end up in such a situation. This paper offers insights into an effect of mega event regeneration projects that has been largely overlooked in the literature, i.e., the expected housing relocation outcomes. The research calls for government intervention and public attention to this important behavioural aspect of mega-event effects.This is the accepted manuscript for a paper published in Habitat International Volume 47, June 2015, Pages 20–28, DOI: 10.1016/j.habitatint.2015.01.00

Volatility clustering in land markets

Purpose– The purpose of this paper is to investigate the volatility clustering in the return of land markets through both theoretical and empirical approaches.Design/methodology/approach– Using extensive monthly panel data at the provincial level from 1986 to 2013, the authors identify the existence of time-correlated and time-varying returns in Canadian land markets.Findings– Consistent with the proposed theory, volatility clustering in land markets tends to be observed in more populated areas.Originality/value– The result has significant implications for portfolio management, economic theory and government policy by revealing the systematic pattern of volatility clustering in land markets.This is the author accepted manuscript. The final version is available from Emerald via http://dx.doi.org/10.1108/PM-02-2014-000

Effects of oxidation temperature on Ga 2O3 film thermally grown on GaN

The effects of oxidation temperature on thermally oxidized GaN film were investigated. The GaN wafers were oxidzied at 750 °C, 800 °C and 850 °C respectively. The electrical characteristics and interface quality of MOS capacitors were compared among different oxidation temperatures. The sample oxidized at 800 °C presented best current-voltage, capacitance-voltage characteristics and smoothest surface morphology, while the higher oxidation temperature of 850 °C gave best interface quality. The electrical breakdown field was increased by one order of magnitude when the sample was oxidized at 800 °C as compared with 750 °C and 850 °C. Lastly, after the sample oxidized at 800 °C was annealed at 850 °C for 10 min, the quality of its oxide was significantly degraded. © 2005 IEEE.published_or_final_versio

Improved I-V characteristics of SiC MOSFETs by TCE thermal gate oxidation

The effects of TCE (trichloroethylene) thermal gate oxidation on the electrical characteristics of SiC MOSFETs are investigated. It is found that TCE thermal gate oxidation can improve the I d-V d characteristics, increase the field-effect mobility, and reduce the threshold voltage and sub-threshold slope of the devices. The better device characteristics are believed to be attributed to the TCE-induced reductions of charges in the gate oxide and traps at the SiO/SiO 2 interface, and also to the gettering of charged impurities and reduction of physical defects by the chlorine incorporated in the gate oxide. ©2005 IEEE.published_or_final_versio

Realization of ultra-wide resonance detection regime of spin-torque diode radio-frequency detector by utilizing tilted fixed-layer magnetization

A novel spin-torque diode radio-frequency detector structure based on tilted fixed-layer magnetic tunnel junction (MTJ) is proposed in this study. The MTJ sandwich structure is composed of NiFe free layer, FePt fixed layer, and MgO interlayer. In order to sense RF signals of different frequencies, both the spin-transfer-torque effect and the alternating-voltage-controlled magnetic anisotropy effect are integrated into the simulation. Results demonstrate that tilting the fixed-layer magnetization can drastically increase the resonance detection regime.postprin

Magnetic-field-sensing mechanism based on dual-vortex motion and magnetic noise

published_or_final_versio

Kinetics of thermal oxidation of 6H silicon carbide in oxygen plus trichloroethylene

In this work, the behaviors of the trichloroethylene (TCE) thermal oxidation of 6H silicon carbide (SiC) are investigated. The oxide growth of 6H SiC under different TCE concentrations (ratios of TCE to O2) follows the linear-parabolic oxidation law derived for silicon oxidation by Deal and Grove, J. Appl. Phys., 36 (1965). The oxidation rate with TCE is much higher than that without TCE and strongly depends on the TCE ratio in addition to oxidation temperature and oxidation time. The increase in oxidation rate induced by TCE is between 2.7 and 67% for a TCE ratio of 0.001-0.2 and a temperature of 1000-1150°C. Generally, the oxidation rate increases quickly with the TCE ratio for a TCE ratio less than 0.05 and then gradually saturates for a ratio larger than 0.05. The activation energy EB/A of the TCE oxidation for the TCE ratio range of 0.001-0.2 is 1.04-1.05 eV, which is a little larger than the 1.02 eV of dry oxidation. A two-step model for the TCE oxidation is also proposed to explain the experimental results. The model points out that in the SiC oxidation with TCE, the products (H2O and Cl2) of the reaction between TCE and O2 can speed up the oxidation, and hence, the oxidation rate is highly sensitive to the TCE ratio. © 2005 The Electrochemical Society. All rights reserved.published_or_final_versio

Edge effect on thermally excited mag-noise in magnetic tunnel junction sensors

Session AP - Magnetic Tunnel Junctions and Spin Valves (Poster Session): no. AP-14This journal issue contains selected papers from the 2012 International Magnetics (INTERMAG) ConferenceThermally excited magnetic noise (mag-noise) has gradually become a major concern in magnetic tunnel junction sensors. By conducting micromagnetic simulation, the spatial distribution of thermal mag-noise in the free layer (FL) was obtained under various hard bias (HB) field and applied field. It was demonstrated that the edges are the main contributor of thermal mag-noise in the FL. This result could be explained by the nonuniform distribution of the stiffness field around the edges. It was also found that both HB field and applied field could suppress the thermal mag-noise in edges. A relatively high applied field will decrease the influence of HB field on mag-noise in the edges. © 2012 IEEE.published_or_final_versionThe IEEE International Magnetics Conference (INTERMAG 2012), Vancouver, BC., 7-11 May 2012. In IEEE Transactions on Magnetics, 2012, v. 48 n. 11, p. 2831-283