Joan Juvert

Comparison of electrical and electro-optical characteristics of light-emitting capacitors based on silicon-rich Si-oxide fabricated by plasma-enhanced chemical vapor deposition and ion implantation

This work presents electrical and electro-optical studies performed on light-emitting capacitors with silicon-rich silicon oxide fabricated by plasma-enhanced chemical vapor deposition and by the implantation of Si ions in thermally grown SiO2. The influence of the fabrication technique and silicon content on electrical, electro-optical, and emission spectra characteristics has been studied. Results on the electrical behavior show a significant dependence on both the fabrication technique and Si content that translates in variations on electroluminescence with fabrication technique and silicon excess.

Manipulating and assembling metallic beads with Optoelectronic Tweezers

Optoelectronic tweezers (OET) or light-patterned dielectrophoresis (DEP) has been developed as a micromanipulation technology for controlling micro- and nano-particles with applications such as cell sorting and studying cell communications. Additionally, the capability of moving small objects accurately and assembling them into arbitrary 2D patterns also makes OET an attractive technology for microfabrication applications. In this work, we demonstrated the use of OET to manipulate conductive silver-coated Poly(methyl methacrylate) (PMMA) microspheres (50 μm diameter) into tailored patterns. It was found that the microspheres could be moved at a max velocity of 3200 μm/s, corresponding to 4.2 nano-newton (10−9 N) DEP force, and also could be positioned with high accuracy via this DEP force. The underlying mechanism for this strong DEP force is shown by our simulations to be caused by a significant increase of the electric field close to the particles, due to the interaction between the field and the silver shells coating the microspheres. The associated increase in electrical gradient causes DEP forces that are much stronger than any previously reported for an OET device, which facilitates manipulation of the metallic microspheres efficiently without compromise in positioning accuracy and is important for applications on electronic component assembling and circuit construction.

DC Electroluminescence Efficiency of Silicon Rich Silicon Oxide Light Emitting Capacitors

We analyze the influence of the fabrication technique and the silicon excess on the power efficiency and evolution with time of the electroluminescence of silicon rich silicon oxide in metal-oxide-semiconductor like light emitting capacitors under direct current. The silicon rich silicon oxide layers have been fabricated using two different techniques, namely plasma enhanced chemical vapor deposition and silicon ion implantation. Six different silicon excesses have been studied, ranging from 6 at. % to 15 at. %. It is shown that both the power efficiency and external quantum efficiency increase with the silicon excess due to a decrease in the electroluminescence current threshold. The maximum value of the power efficiency has been found to be (2.6±0.3)×10-5 in the ion implanted sample with 15 at. % silicon excess. Significant differences in the evolution of the electroluminescence with time are found depending on the fabrication technique.

A low-cost technique for adding microlasers to a silicon photonic platform

In this paper we report the physical micromanipulation of standard InP telecommunications laser die in a liquid medium by means of optoelectronic tweezers. Optoelectronic tweezers have been shown to use much less optical power than optical tweezers, they do not require a coherent light source to function and the creation of multiple traps is straightforward. These properties make the technique a very good candidate for the massive parallel micromanipulation of optoelectronic components for assembly on a photonic platform. We discuss the positional and orientation accuracy of the optoelectronic tweezers in relation to the alignment requirements for low-loss coupling between the light sources and the other components in a photonic platform. Our experiments indicate that the accuracy is better than 2 μm and 2° for translations and rotations, respectively.

Influence by Layer Structure on the Output EL of CMOS Compatible Silicon-Based Light Emitters

Fully combined metal-oxide-semiconductor compatible light-emitting devices based on nano bi-layer structures are fabricated. The active layers are composed of silicon nitride on top of a silicon-enriched silicon dioxide film with different Si concentrations. Electro and photo luminescence spectra of the devices and the active materials are analyzed and correlated to verify if the origin of the emission is the same. Differences found between electrically and optically stimulated photo-emission in the studied region of the spectra are concluded to be due to optical phenomena introduced by the gate and multilayer configuration, meaning that the same radiative centers are stimulated optically and electrically.

Micromanipulation of InP lasers with optoelectronic tweezers for integration on a photonic platform

The integration of light sources on a photonic platform is a key aspect of the fabrication of self-contained photonic circuits with a small footprint that does not have a definitive solution yet. Several approaches are being actively researched for this purpose. In this work we propose optoelectronic tweezers for the manipulation and integration of light sources on a photonic platform and report the positional and angular accuracy of the micromanipulation of standard Fabry-Pérot InP semiconductor laser die. These lasers are over three orders of magnitude bigger in volume than any previously assembled with optofluidic techniques and the fact that they are industry standard lasers makes them significantly more useful than previously assembled microdisk lasers. We measure the accuracy to be 2.5 ± 1.4 µm and 1.4 ± 0.4° and conclude that optoelectronic tweezers are a promising technique for the micromanipulation and integration of optoelectronic components in general and semiconductor lasers in particular.

Use of optoelectronic tweezers in manufacturing—accurate solder bead positioning

In this work, we analyze the use of optoelectronic tweezers (OETs) to manipulate 45 μm diameter Sn62Pb36Ag2 solder beads with light-induced dielectrophoresis force and we demonstrate high positioning accuracy. It was found that the positional deviation of the solder beads increases with the increase of the trap size. To clarify the underlying mechanism, simulations based on the integration of the Maxwell stress tensor were used to study the force profiles of OET traps with different sizes. It was found that the solder beads felt a 0.1 nN static friction or stiction force due to electrical forces pulling them towards the surface and that this force is not dependent on the size of the trap. The stiction limits the positioning accuracy; however, we show that by choosing a trap that is just larger than the solder bead sub-micron positional accuracy can be achieved.

The effect of absorption and coherent interference in the photoluminescence and electroluminescence spectra of SRO/SRN MIS capacitors

In this paper we present a technique that can be used to study the effect of absorption and coherent interference in the luminescence of multilayer structures. We apply the technique to the measured photoluminescence and electroluminescence spectra of MIS capacitors where the insulator is composed of a silicon rich oxide (SRO)/silicon rich nitride (SRN) bilayer structure. We remove the effect of the multilayer stack on the measured photoluminescence spectrum of the samples without the metal contact to find the intrinsic spectrum. Then we apply the effect of the MIS structure on the intrinsic spectrum in order to calculate the electroluminescence spectrum. Good agreement with the experimentally measured EL spectrum is found. We discuss which parameters affect the spectra most significantly.

Blue and red electroluminescence of silicon-rich oxide light emitting capacitors

Electroluminescent properties of thin silicon-rich oxide (SRO) films deposited by low pressure chemical vapor deposition (LPCVD) were studied. The gas flow ratio Ro = N2O/SiH4 was changed to obtain different silicon concentrations within the SRO films. After deposition, SRO films were thermally annealed at 1100ºC for 3h in N2 atmosphere in order to create silicon nanoparticles (Si-nps). Simple capacitive structures like Polysilicon/SRO/n-Si were used for the study. These light emitting capacitors (LECs) show intense blue (~466) and red EL (~685) at room temperature depending on the silicon excess within the SRO films. Electroluminescence in these LECs is obtained at direct current (DC) at both forward and reverse bias conditions. Nevertheless, a stronger whole area EL is obtained when devices are forwardly biased.

Integration of III-V light sources on a silicon photonics circuit by transfer printing

We report on the integration by transfer printing of III-V Fabry-Perot cavities on a silicon photonic circuit. We pre-process the III-V coupons on their native substrate, transfer print onto the target SOI, and post-process the printed coupons. We report light coupling into the photonic circuit.