1,721,117 research outputs found
Photoluminescence from (Si/SiO2)n superlattices and their use as emitters in [SiO2/Si]n SiO2 [Si/SiO2]m microcavities
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Spectral- and time-resolved electroluminescence of silicon nanocrystals based light emitting devices
No full textIn this work we study the electroluminescence (EL) from a high efficiency multilayered
silicon nanocrystals light emitting diode. The spectral analysis of EL under dc condition shows
a spectrally modulated optical emission. Through reflectivity measurements we evaluated the
effects of interference on the EL lineshape due to device structure and ascribed the emission to
recombination in size dispersed silicon nanocrystals (Si-NCs). By studying the time resolved
current–voltage I–V and EL-V, we evidenced that injected carriers are both accumulated
separately and concurrently in Si-NCs. At the bias transition the accumulated carriers either
are extracted from the gate oxide giving rise to a short current pulse or they diffuse to large
Si-NCs giving rise to an EL overshoot which decays with μs time constant
Role of the inversion layer on the charge injection in silicon nanocrystal multilayered light emitting devices
No full textThe role of the inversion layer on injection and recombination phenomena in light emitting diodes (LEDs) is here studied on a multilayer (ML) structure of silicon nanocrystals (Si-NCs) embedded in SiO2. Two Si-NC LEDs, which are similar for the active material but different in the fabrication process, elucidate the role of the non-radiative recombination rates at the ML/substrate interface. By studying current- and capacitance-voltage characteristics as well as electroluminescence spectra and time-resolved electroluminescence under pulsed and alternating bias pumping scheme in both the devices, we are able to ascribe the different experimental results to an efficient or inefficient minority carrier (electron) supply by the p-type substrate in the metal oxide semiconductor LEDs
CMOS compatible Si/SiO2 multilayers for Light Emitting Diodes
No full textWe report photoluminescence and electroluminescence at room temperature in diodes based on Si/SiO2 multilayers. The multilayers are fabricated by alternating Si and SiO2 layers, whose thickness is, respectively, 3.5 and 5 nanometers. In photoluminescence, a single band is observed, centered at 800 nm, which is due to electron-hole pair recombination under quantuum confinement. on the other hand, in electroluminescence, two bands are reported. The first band is in the infrared spectrum, and is blackbody radiation. The second band is visible, and is originated by relaxation of a single type of electrical carrier (electrons), as suggested by a fast decay time (less than 0.1 s). Possible mechanisms can be hot-electron relaxation or coupling with surface plasmon-polariton
Visible light emission from a new material system: Si/SiO2 superlattices in optical microcavities
No full textIn order to add optical functionalities to silicon based microelectronics, we decided to develop Si/SiO2 superlattices where quantum confinement effects should drive Si to become a good emitter. A further improvement is possible when one couples the beneficial effects of low dimensional electronic systems (as in Si superlattices) with the enhancement of the spontaneous emission rate that occurs in an optical microcavity. Not to lose the fundamental goal to add optical functionality to electronic circuits we have performed the growth of this material in an industrial environment by using standard CMOS equipments. In this paper we will present the status of our researc
Optical characterization of silicon nitride low-loss waveguides in the near infrared range
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Are on-chip heralded single photon sources possible by intermodal four wave mixing in silicon waveguides?
No full textOn-chip heralded single photon sources are of key importance in the development of chip-scale devices exploiting the quantum properties of light. Single photon states can be produced as single photons heralded from correlated photon pairs generated through spontaneous four wave mixing. On-chip heralded single photon sources based on spontaneous four wave mixing have been already demonstrated. However, the heralded and herald photons are usually generated with wavelengths very close to the pump one, limiting the pump rejection efficiency and the application to the mid infrared. Moreover, the common sources of heralded photons based on spontaneous four wave mixing require spectral post filtering to achieve high purity, limiting the brightness and the integration of these sources. A solution to these problems can be provided by intermodal four wave mixing. In this work, we demonstrate the generation of photon pairs through intermodal four wave mixing in silicon waveguides, measuring the coincidences between the idler at 1.281 μm and the signal at 1.952 μm. We then discuss the application of intermodal four wave mixing to on-chip heralded single photon sources
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