High Electron Mobility InN

Irradiation of InN films with 2 MeV He+ ions followed by thermal annealing below 500 °C creates films with high electron concentrations and mobilities, as well as strong photoluminescence. Calculations show that electron mobility in irradiated samples is limited by triply charged donor defects. Subsequent thermal annealing removes a fraction of the defects, decreasing the electron concentration. There is a large increase in electron mobility upon annealing; the mobilities approach those of the as-grown films, which have 10 to 100 times smaller electron concentrations. Spatial ordering of the triply charged defects is suggested to cause the unusual increase in electron mobility

High Electron Mobility InN

ABSTRACT Irradiation of InN films with 2 MeV He + ions followed by thermal annealing below 500 o C creates films with high electron concentration and mobility, as well as strong photoluminescence. Calculations show that electron mobility in irradiated samples is limited by triply charged donor defects. Subsequent thermal annealing removes a fraction of the defects, decreasing the electron concentration. There is a large increase in electron mobility upon annealing; the mobilities approach those of the as-grown films, which have 10 to 100 times smaller electron concentrations. Spatial ordering of the triply charged defects is suggested to cause the unusual increase in electron mobility

Exceptional Electron Transport Properties of In-rich InGaN

Recent years have seen an explosion of interest in the narrow band gap end of the InGaN alloy system, particularly in InN. The existence of surface electron accumulation and a tendency for n-type conductivity have been well-established and are explained by an extremely large electron affinity and the location of the Fermi level stabilization energy (E{sub FS}) high in the conduction band [1]. These characteristics pose significant challenges to the integration of In-rich InGaN into devices and demonstrate the need for a better understanding of the relationship between native defects and electronic transport in the alloy system. It has been previously shown that high-energy particle irradiation can predictably control the electronic properties of In-rich InGaN [1]. With increasing irradiation dose, the electron concentration (n) increases and the electron mobility ({mu}) decreases until the Fermi level reaches E{sub FS}, which is the saturation point. The value of n at saturation decreases with decreasing In fraction, due to the raising of the conduction band edge with respect to E{sub FS}

Defect Doping of InN

InN films grown by molecular beam epitaxy have been subjected to 2 MeV He{sup +} irradiation followed by thermal annealing. Theoretical analysis of the electron mobilities shows that thermal annealing removes triply charged donor defects, creating films with electron mobilities approaching those predicted for uncompensated, singly charged donors. Optimum thermal annealing of irradiated InN can be used to produce samples with electron mobilities higher than those of as grown films

Removal of hexavalent chromium of contaminated soil by coupling electrokinetic remediation and permeable reactive biobarriers

PURPOSE: In this study, a novel and ecological alternative have been developed to treat soils contaminated with hexavalent chromium coupling two well-known systems: electrokinetic remediation and permeable reactive biobarriers. The electric field promotes the electromigration of the hexavalent chromium oxyanions towards the anode. The biobarriers were placed before the anode electrode, in order to promote the reduction and retention of the chromium migrating in its direction. Thus, this technology provided a global treatment to soil removal without subsequent treatments of the contaminated effluents. METHODS: The electrokinetic system was coupled with two different permeable reactive biobarriers composed by Arthrobacter viscosus bacteria, supported either in activated carbon or zeolite. An electric field of 10 V was applied and two different treatment times of 9 and 18 days were tested. RESULTS: Removal values of 60% and 79% were obtained when electrokinetic treatment was coupled with zeolite and activated carbon biobarriers, respectively, for a test period of 18 day. The reduction of hexavalent chromium to trivalent chromium was around 45% for both systems. CONCLUSIONS: In this work, two types of biobarriers were efficiently coupled to electrokinetic treatment to decontaminate soil with Cr(VI). Furthermore, the viability of the new coupling technology developed (electrokinetic + biobarriers) to treat low-permeability polluted soils was demonstrated.This work was supported by the Spanish Ministry of Science and Innovation (CTQ2008-03059/PPQ), Xunta de Galicia (08MDS034314PR). The authors are grateful to the Spanish Ministry of Science and Innovation for providing financial support for Marta Pazos under the Ramon y Cajal program and the Fundacao para a Ciencia e Tecnologia, Ministerio da Ciencia e Tecnologia, Portugal through the PhD grant of Bruna Fonseca (SFRH/BD/27780/2006)