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Abstract:

Modification of the band structure of single-walled carbon nanotubes (SWNTs) through encapsulation of the inorganic material manganese ditelluride (MnTe2) is reported. We show that this leads to a global reduction of their 1st (E11^S) and 2nd (E22^S) band gap energies by a similar percentage (up to 3.8%) and interpret this as due to a lowering of the carbon-carbon transfer integrals. © 2007 American Institute of Physics.

Abstract:

We present a systematic investigation of free-carrier screening in coupled asymmetric GaN quantum discs with embedded AlGaN barriers using time-integrated and time-resolved micro-photoluminescence measurements, supported by three-dimensional multi-band k.p computational modeling. Free-carrier screening effects decreased with the barrier thickness, which indicates that the source of the free-carriers were carriers tunneling through the barrier. © 2007 American Institute of Physics.

Abstract:

Micro-photoluminescence properties of single InGaN/GaN quantum dots (QDs) are investigated using sub-bandgap excitation by 1 ps pulses from a Ti:sapphire laser. This results in almost complete suppression of background emission arising from the underlying quantum well to which the QDs are coupled. Photoluminescence excitation spectra undertaken using this technique show evidence of p-states. The non-linear intensity dependence of the emission is also discussed. © 2007 American Institute of Physics.

Abstract:

By using two-photon absorption spectroscopy we have performed time-integrated and time-resolved photoluminescence measurements on several coupled asymmetric GaN quantum discs, with embedded AlGaN barriers. We observe free-carrier screening, with an enhancement due to tunneling between the coupled quantum discs. © 2007 American Institute of Physics.

Abstract:

Selective area growth (SAG) of GaN by hydride vapor phase epitaxy (HVPE) has been performed on SiO2 stripe-mask-patterned Si(111) substrates with various buffer layers. AlGaN, GaN and AIN films were used as buffer layers. In order to grow selectively, the orientation of the SiO2 mask pattern was opened along the Si (110) direction. The properties of the SAG-GaN samples were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), and photoluminescence(PL). SEM images show that hexagonal SAG-GaN grows vertically along the < 0001 > direction, longitudinally along the < 11 (2) over bar0 > direction with facets on the sidewall growing along the (1 (1) over bar 01) direction. It was found that the lateral-to-vertical growth ratio depended strongly on different buffer layers.