Effect of grain size and hydrogen passivation on the electrical properties of nanocrystalline silicon films

The properties of mixed-phase (nanocrystalline/amorphous) silicon layers produced by reactive RF-sputtering are described. The chemical composition and nanostructure [i.e. nanocrystal (NC) size and volume fraction] of the films were studied by Rutherford backscattering spectroscopy (RBS) and micro-Raman spectroscopy, respectively. Samples with different fractions of the nanocrystalline phase and NC mean size were produced by changing the deposition parameters, without post-growth annealing. The electrical conductivity of the films, measured as function of temperature, is discussed in relation to their nanostructureFCT Project POCTI/CTM/39395/200

Light emission and spin-polarised hole injection in InAs/GaAs quantum dot heterostructures with Schottky contact

EPL draftWe demonstrate the feasibility to obtain electroluminescence (EL), up to room temperature, from InGaAs self-assembled quantum dots (QDs) included in a forward-biased Schottky diode. Moreover, using a ferromagnet (FM) as the contact layer, sizable circular polarization of the EL emission in the presence of an external magnetic eld is obtained. A resonant behav- ior of the degree of circular polarization (P) as a function of applied voltage (V ), for a given value of magnetic eld, is observed. We explain our ndings using a model including tunneling of (spin-polarised) holes through the metal-semiconductor interface, transport in the near surface region of the heterostructure and out-of-equilibrium statistics of the injected carriers occupying the available states in the QD heterostructure. In particular, the resonant P(V ) dependence is related to the splitting of the qusi-Fermi level for two spin orientations in the FM.FCT, Portugal (project POCI/FIS/58524/2004), the RFBR, Russia (grant 10-02- 00501), MEC (grants MAT2008-01555, QOIT-CSD2006- 00019) and CAM (S-2009/ESP-1503) (Spain)

Investigation of photoconductivity of individual InAs/GaAs(001) quantum dots by Scanning Near-field Optical Microscopy

Исследовано распределение фототока по поверхности Ga s p–i–n диода cо встроенными квантовыми точками (КТ) In s при фотовозбуждении зондом сканирующего ближнепольного оптического микроскопа (СБОМ). На СБОМ изображениях фототока наблюдались неоднородности, связанные с межзонным поглощением в КТ.The photocurrent distribution in GaAs p–i–n diode with embedded InAs quantum dots (QDs) was studied with the photoexcitation through a Scanning Near-field Probe Microscope (SNOM) probe. The inhomogeneities related to the interband absorption in the QDs were observed in the photocurrent SNOM images.Работа выполнена при поддержке РФФИ (16-02-00450)