dopage Si des BQs

Nanowires and nanotubes carry charge and excitons efficiently, and are therefore potentially ideal building blocks for nanoscale electronics and optoelectronics1, 2. Carbon nanotubes have already been exploited in devices such as field-effect3, 4 and single-electron5, 6 transistors, but the practical utility of nanotube components for building electronic circuits is limited, as it is not yet possible to selectively grow semiconducting or metallic nanotubes7, 8. Here we report the assembly of functional nanoscale devices from indium phosphide nanowires, the electrical properties of which are controlled by selective doping. Gate-voltage-dependent transport measurements demonstrate that the nanowires can be predictably synthesized as either n- or p-type. These doped nanowires function as nanoscale field-effect transistors, and can be assembled into crossed-wire p–n junctions that exhibit rectifying behaviour. Significantly, the p–n junctions emit light strongly and are perhaps the smallest light-emitting diodes that have yet been made. Finally, we show that electric-field-directed assembly can be used to create highly integrated device arrays from nanowire building blocks.

The optical properties of GaN nanowires grown by catalyst free plasma-assisted molecular beam epitaxy on Si (111) are investigated by photoluminescence (PL) spectroscopy. The influence of the Si- and Mg-flux as well as the III-V ratio during growth on the PL properties is discussed. The Mg concentration as determined by secondary ion mass spectroscopy ranges from 5×1018 to 1×1020 cm−3. Raman scattering reveals that the nanowires are strain-free, irrespective of Si- or Mg-doping. The near band-edge emission of undoped or slightly Si-doped material is dominated by the narrow D0X recombination at 3.4715 eV with a full width at half maximum of 1.5 meV at 4 K. For high Si-fluxes, a blueshift of the D0X peak by 1 meV is found, which is attributed to band-filling effects. For moderate Mg-fluxes the acceptor-bound exciton recombination was detected at 3.4665 eV. Point defects due to the N-rich growth conditions are discussed as the origin of the emission band at 3.45 eV. Recombination at coalescence boundaries were identified as the origin of an emission band at 3.21 eV. The luminescence properties below 3.27 eV in highly Mg-doped samples are shown to be affected by the presence of cubic inclusions in the otherwise wurtzite nanowires.

We have studied the effect of impurity doping on the optical properties of indium phosphide (InP) nanowires. Photoluminescence measurements have been performed on individual nanowires at low temperatures (5–70 K) and at low excitation intensities (0.5–10 W/cm2). We show that the observed redshift (200 meV) and the linewidth (70 meV) of the emission of p-type InP wires are a result of a built-in electric field in the nanowires. This bandbending is induced by Fermi-level pinning at the nanowire surface. Upon increasing the excitation intensity, the typical emission from these p-InP wires blueshifts with 70 meV/decade, due to a reduction of the bandbending induced by an increase in the carrier concentration. For intrinsic and n-type nanowires, we found several impurity-related emission lines.

Zeitungsbericht "El Pais" über Aktivitäten von Dr. Fuentes von 1985 (!)

Beschreibung Olympia 1 Marathonlauf: Sieger mit Auto gefahren, 2. mit Strychnin gedopt.