The effect of GaN and ain buffer layers on GaN film properties grown on both C-plane and A-plane sapphire

This paper presents a comparative study of the properties of GaN grown by organometallic vapor phase epitaxy, using both a GaN and A1N buffer layer, as a function of sapphire orientation (c-plane vs a-plane). Results are presented for varying the thickness of the buffer layer, varying the growth temperature of the GaN film, and also varying the ammonia/trimethylgallium mass flow ratio. The electron Hall mobilities of GaN films grown on an A1N buffer layer were, in general, higher compared to films grown using a GaN buffer layer. In addition, growth on a-plane sapphire resulted in higher quality films (over a wider range of buffer thicknesses) than growth on c-plane sapphire. The room temperature electron mobilities were also found to be dependent on, not only the growth temperature, but also the ammonia/trimethylgallium mass flow ratio.     

The effect of organometallic vapor phase epitaxial growth conditions on wurtzite GaN electron transport properties

The growth issues known to effect the quality of GaN organometallic vapor phase epitaxial films are reviewed and the best 300Kmobility vs electron concentration data are discussed. The data probably represent transport properties intrinsic to films grown on sapphire. From the results of Hall measurements, the unintentional donor in high quality GaN films cannot be Si since the donor ionization energy is much larger than that of films intentionally doped with Si (36 vs 26 meV). Electrical properties of a doped channel layer are shown not to be significantly different from those of thick films which implies a viable technology for conducting channel devices. It is argued that 77K Hall measurements are a useful indicator of GaN film quality and a compilation of unintentionally and Si doped data is presented. The 77K data imply that, at least over a limited range, Si-doping does not appreciably change the compensation of the GaN. The 77K data indicate that the low mobilities of films grown at low temperatures are probably not related to dopant impurities.     

Comparison of factor structures and criterion-related validity coefficients for two measures of personality based on the five factor model.

The factor structure and criterion-related validity for 2 types of personality measures that are based on 5 factor models were studied. Confirmatory factor analysis was used to compare a 5 versus 6 factor model in an applied setting. In addition, criterion-related validity coefficients were examined for the 2 inventories. Two Big Five measures were used—1 was an adjective-based bipolar inventory and the other was a questionnaire (NEO-Personality Inventory; PI)—to shed light on the relationships between inventory characteristics, factor structure, and criterion-related validity. The sample consisted of 423 flight attendant trainees. Results indicated that the 6 factor model provided a better fit for both measures compared with the 5 factor model. Scales from the NEO-PI were significantly correlated with measures of training success, whereas scales from the bipolar inventory were not. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Emotional labor in American professors.

An online survey was conducted on a national sample of United States professors to examine emotional labor and its relationship to work outcomes. Participants were queried on genuine, faking, and suppressing emotional expression facets of emotional labor, as well as emotional exhaustion, job satisfaction, and affective commitment. The sample of 598 included 71 instructors, 177 assistant professors, 168 associate professors, and 182 professors. A path analysis was conducted testing two models of emotional labor. Results supported a model indicating significant direct relationships between emotional labor, emotional exhaustion, and job satisfaction. Additionally, the relationship between emotional labor and affective commitment was mediated by emotional exhaustion and job satisfaction. Genuine positive expression was the only emotional labor variable to have significant direct relationships with all outcomes. For U.S. faculty, the experience of emotional labor was related to several work attitudes. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Doping of gallium nitride using disilane

The silicon doping of n-type GaN using disilane has been demonstrated for films grown on sapphire substrates by low pressure organometallic vapor phase epitaxy. The binding energy of an exciton bound to a neutral Si donor has been determined from low temperature (6K) photoluminescence spectra to be 8.6 meV. Nearly complete activation of the Si impurity atom in the GaN lattice has been observed.     

Challenges for MPLS in optical network restoration

Previous standards proposals have focused on extending IP-based MPLS protocols to optical networks. These proposals have concentrated on provisioning optical connections. However, a key expectation of the optical network is that it will offer fast restoration capability, competitive in performance to SONET rings. To meet this expectation, there are key features that need to be added to the current proposals to extend MPLS for the optical network. This article discusses some of these key requirements     

Introduction

Telecommunication Systems -