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See detailInvestigation on Localized States in GaN Nanowires
Polenta, L. UL; Rossi, M.; Cavallini, Anna et al

in ACS Nano (2008), 2

GaN nanowires with diameters ranging between 50 and 500 nm were investigated by electrical and photoinduced current techniques to determine the influence of their size on the opto-electronic behavior of ... [more ▼]

GaN nanowires with diameters ranging between 50 and 500 nm were investigated by electrical and photoinduced current techniques to determine the influence of their size on the opto-electronic behavior of nanodevices. The conductivity, photoconductivity, and persistent photoconductivity behavior of GaN nanowires are observed to strongly depend on the wire diameter. In particular, by spectral photoconductivity measurements, three main sub-band-gap optoelectronic transitions were detected, ascribed to the localized states giving rise to the characteristic blue, green, and yellow bands of GaN. Photoconductivity with below-band-gap excitation varies orders of magnitude with the wire diameter, similarly to that observed for near-band-edge excitation. Moreover, yellow-band-related signal shows a superlinear behavior with respect to the band-edge signal, offering new information for the modeling of the carrier recombination mechanism along the nanowires. The photoconductivity results agree well with a model which takes into account a uniform distribution of the localized states inside the wire and their direct recombination with the electrons in the conduction band. [less ▲]

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See detailGaN-nanowhiskers: MBE-growth conditions and optical properties
Meijers, R.; Richter, T.; Calarco, R. et al

in Journal of Crystal Growth (2006), 289(1), 381-386

Morphology and optical properties of GaN nanowhiskers grown by molecular beam epitaxy(MBE) have been studied in correlation with growth parameters. It was shown that the growth parameters can be tuned ... [more ▼]

Morphology and optical properties of GaN nanowhiskers grown by molecular beam epitaxy(MBE) have been studied in correlation with growth parameters. It was shown that the growth parameters can be tuned such that uniform, well separated and high-quality nanowhiskers are obtained. Using an optimized ramp of Ga beam equivalent pressure (BEP) during the growth, the tapering or coalescence of nanowhiskers can be suppressed. By increasing the growth temperature the density of nanowhiskers is reduced, but the crystalline quality is improved as can be concluded from cathodoluminescence (CL) results. [less ▲]

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See detailGaN Nanocolumns on Si(111) Grown b Molecular Beam Epitaxy
Calarco, Raffaella; Marso, Michel UL; Meijers, R. et al

in Proc. 5th Intern. Conf. Advanced Semicon. Dev. & Microsystems ASDAM’04 (2004)

GaN nanocolumns are reproducibly grown by plasma-assisted molecular beam epitaxy on Si(111). The nanocolumn density and diameter, 20–150 nm, are controlled by means of the III/V ratio. The nanocolumns ... [more ▼]

GaN nanocolumns are reproducibly grown by plasma-assisted molecular beam epitaxy on Si(111). The nanocolumn density and diameter, 20–150 nm, are controlled by means of the III/V ratio. The nanocolumns grow parallel to the [111] direction of the Si substrate. The columns have been transferred to a Si(100) substrate covered with a layer of 300nm SiO2; single nanowire devices have been fabricated using finger shaped electrical contacts (Ti/Au) obtained by e-beam patterning technique. The electrical transport properties of the resulting metal–semiconductor–metal nanostructures are analyzed by means of current– voltage measurements with and without UV-illumination. [less ▲]

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