Evidence for impact ionisation in AlGaN/GaN HEMTs with InGaN back-barrier

Electroluminescence (EL) spectroscopy in combination with drift-diffusion simulations was used to prove the presence of impact ionisation in AlGaN/GaN HEMTs illustrated on InGaN back-barrier devices. Regardless of the level of gate leakage current, which is dominated by contributions such as surface leakage current and others, EL enabled the revealing of hole generation due to impact ionisation. Hole currents as low as 10pA were detectable by the optical technique used.United States. Office of Naval Research Global (N00014-08-1-1091

Electrical characterization and nanoscale surface morphology of optimized Ti/Al/Ta/Au ohmic contact for AlGaN/GaN HEMT

Good ohmic contacts with low contact resistance, smooth surface morphology, and a well-defined edge profile are essential to ensure optimal device performances for the AlGaN/GaN high electron mobility transistors [HEMTs]. A tantalum [Ta] metal layer and an SiNx thin film were used for the first time as an effective diffusion barrier and encapsulation layer in the standard Ti/Al/metal/Au ohmic metallization scheme in order to obtain high quality ohmic contacts with a focus on the thickness of Ta and SiNx. It is found that the Ta thickness is the dominant factor affecting the contact resistance, while the SiNx thickness affects the surface morphology significantly. An optimized Ti/Al/Ta/Au ohmic contact including a 40-nm thick Ta barrier layer and a 50-nm thick SiNx encapsulation layer is preferred when compared with the other conventional ohmic contact stacks as it produces a low contact resistance of around 7.27 × 10-7 Ω·cm2 and an ultra-low nanoscale surface morphology with a root mean square deviation of around 10 nm. Results from the proposed study play an important role in obtaining excellent ohmic contact formation in the fabrication of AlGaN/GaN HEMTs

Consumer Adoption of Self-Service Technologies in the Context of the Jordanian Banking Industry: Examining the Moderating Role of Channel Types

YesThis study aimed to examine the key factors predicting Jordanian consumers’ intentions and usage of three types of self-service banking technologies. This study also sought to test if the impacts of these main predictors could be moderated by channel type. This study proposed a conceptual model by integrating factors from the unified theory of acceptance and use of technology (UTAUT), along with perceived risk. The required data were collected from a convenience sample of Jordanian banking customers using a survey questionnaire. The statistical results strongly support the significant influence of performance expectancy, social influence, and perceived risk on customer intentions for the three types of SSTs examined. The results of the X2 differences test also indicate that there are significant differences in the influence of the main predictors due to the moderating effect of channel type. One of the key contributions of this study is that three types of SSTs were tested in a single study, which had not been done before, leading to the identification of the factors common to all three types, as well as the salient factors unique to each type

An equity analysis of utilization of health services in Afghanistan using a national household survey

Abstract Background Afghanistan has made great strides in the coverage of health services across the country but coverage of key indicators remains low nationally and whether the poorest households are accessing these services is not well understood. Methods We analyzed the Afghanistan Mortality Survey 2010 on utilization of inpatient and outpatient care, institutional delivery and antenatal care by wealth quintiles. Concentration indexes (CIs) were generated to measure the inequality of using the four services. Additional analyses were conducted to examine factors that explain the health inequalities (e.g. age, gender, education and residence). Results Among households reporting utilization of health services, public health facilities were used more often for inpatient care, while they were used less for outpatient care. Overall, the utilization of inpatient and outpatient care, and antenatal care was equally distributed among income groups, with CIs of 0.04, 0.03 and 0.08, respectively. However, the poor used more public facilities while the wealthy used more private facilities. There was a substantial inequality in the use of institutional delivery services, with a CI of 0.31. Poorer women had a lower rate of institutional deliveries overall, in both public and private facilities, compared to the wealthy. Location was an important factor in explaining the inequality in the use of health services. Conclusions The large gap between the rich and poor in access to and utilization of key maternal services, such as institutional delivery, may be a central factor to the high rates of maternal mortality and morbidity and impedes efforts to make progress toward universal health coverage. While poorer households use public health services more often, the use of public facilities for outpatient visits remains half that of private facilities. Pro-poor targeting as well as a better understanding of the private sector’s role in increasing equitable coverage of maternal health services is needed. Equity-oriented approaches in health should be prioritized to promote more inclusive health system reforms

Financial Markets Serve Rural Areas Reasonably Well

Rural financial markets differ from urban markets, but they appear to work reasonably well at supplying credit to rural borrowers. When urban and rural loans are compared, average interest rates, collateral requirements, and other terms are nearly identical. Furthermore, national opinion surveys have generally found that rural borrowers are at least as satisfied with their financial service provider as are urban borrowers. The nature of rural economies— small communities, small borrowers, and undiversified industries— can lead to disparities in the availability of financial services among individual borrowers and communities, but financial market imperfections have not detracted substantially from overall rural growth

Analysis of current collapse effect in AlGaN/GaN HEMT: experiments and numerical simulations

In this work, current collapse effects in AlGaN/GaN HEMTs are investigated by means of measurements and two-dimensional physical simulations. According to pulsed measurements, the used devices exhibit a significant gate-lag and a less pronounced drain-lag ascribed to the presence of surface/barrier and buffer traps, respectively. As a matter of fact, two trap levels (0.45 eV and 0.78 eV) were extracted by trapping analysis based on isothermal current transient. On the other hand, 2D physical simulations suggest that the kink effect can be explained by electron trapping into barrier traps and a consequent electron emission after a certain electric-field is reached

Effects of surface and buffer traps in passivated AlGaN/GaN HEMTs

The physical mechanisms underlying RF current collapse effects in AlGaN-GaN HEMTs are investigated by means of measurements and numerical device simulations. Our study suggests that 1) both surface and buffer traps can contribute to RF current collapse through a similar physical mechanism involving capture/emission of electrons tunneling from the gate; 2) surface passivation strongly mitigate RF current collapse, by reducing the surface electric field and inhibiting electron injection into traps; 3) for surface donor trap densities lower than 9e12 /cm2, surface potential barriers in the 1-2 eV range can coexist with surface traps having much a shallower energy depth and inducing, therefore, current-collapse effects characterized by relatively short time constants