This dissertation investigates challenges associated with optics in the 10-500 wavelength size regime. For the visible spectrum, this size range (5-250um) is classified as micro-optics, but is set apart from other size ranges by a noticeable lack of suitable simulation and metrology tools. Optics of this size are gaining popularity in applications such as solid immersion lenses (SIL) and laser beam shaping, but require more research into simulation, testing, fabrication, and assembly in order to be easily integrated into commercial applications.A survey of previous work on SILs and micro-optics simulation/testing is given, including past work with gallium phosphide (GaP) microlenses. A new SIL aberration treatment is described using spherical-parent 3rd order aberrations. Agreement is shown with previous work, and the lack of hemisphere approximations gives a broader understanding of aberrations for varying SIL thicknesses. Results show that aberration reduces with lens radius, but thickness tolerances become tighter as dimensions shrink. A study of GaP intrinsic birefringence and the theoretical impact on the induced polarization signal is also given.A survey of beam propagation simulators is given and a sequential piece-wise diffraction (SPWD) simulator is developed for arbitrary optical systems that overcomes the difficulties of simulation in the 10-500 wavelength size regime. A discussion of a future extension to the work to determine reflected and transmitted field amplitudes with a non-sequential method is presented with specific discussion on the challenges of electric field surface transfer.The design and operation of a micro-interferometer is discussed and testing results from the first sub-100um diameter GaP SILs are shown. A novel method for determining the shape profile of aspheric surfaces using information from annular fringes is presented. Theoretical beam shaping applications for micro GaP lenses is also discussed with results using the SPWD method. Experimental results are also shown for a 1x1x0.3mm beam shaper package that images a laser diode beam to an approximate size of 60um at a working distance of 4mm.Finally, designs and experimental results are shown for the integration of GaP micro-optics into conventional systems as SILs or beam-shaping elements including methods and equipment for lapping and polishing GaP.

abstract: Nanowires are 1D rod-like structures which are regarded as the basis for future technologies. III-V nanowires have attracted immense attention because of their stability, crystal quality and wide use. In this work, I focus on the growth and characterization of III-V semiconductor nanowires, in particular GaP, InP and InGaP alloys. These nanowires were grown using a hot wall CVD(Chemical Vapor Deposition) setup and are characterized using SEM (Scanning Electron Microscope), EDX (Energy Dispersive X-ray Spectroscopy) and PL (Photoluminescence) techniques. In the first chapter, Indium Phosphide nanowires were grown using elemental sources (In and P powders). I consider the various kinds of InP morphologies grown using this method. The effect of source temperature on the stoichiometry and optical properties of nanowires is studied. Lasing behavior has been seen in InP nanostructures, showing superior material quality of InP. InGaP alloy nanowires were grown using compound and elemental sources. Nanowires grown using compound sources have significant oxide incorporation and showed kinky morphology. Nanowires grown using elemental sources had no oxide and showed better optical quality. Also, these samples showed a tunable alloy composition across the entire substrate covering more than 50% of the InGaP alloy system. Integrated intensity showed that the bandgap of the nanowires changed from indirect to direct bandgap with increasing Indium composition. InGaP alloy nanowires were compared with Gallium Phosphide nanowires in terms of PL emission, using InGaP nanowires it is possible to grow nanowires free of defects and oxygen impurities, which are commonly encountered in GaP nanowires. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2016

No description available.

The high degree of control over the morphology and optoelectronic properties of semiconductor nanowires (NWs) makes them attractive for applications such as thermoelectrics, quantum emitters, and photodetectors. However, NW growth is still not fully understood as many parameters play a role in the determination of NW morphology and crystal structure, which in turn governs resulting optoelectronic properties. We report tellurium-doped GaP NWs with positive tapering and radii measuring as low as 5 nm grown by the self-assisted vapor–liquid–solid mechanism using selective-area molecular beam epitaxy. The occurrence of ultrathin nanoantenna showed a dependence on pattern pitch (separation between NWs) with a predominance at 600 nm pitch, and exhibited radius oscillations that correlate with polytypic zincblende (ZB)/wurtzite (WZ) segments. A growth model explains the positive tapering of the NW leading to an ultrathin tip from the suppression of surface diffusion of Ga adatoms on the NW sidewalls by Te dopant flux. The model also provides a relationship between the radius modulations and the oscillations of the droplet contact angle, predicting the quasi-periodic radius oscillations and corresponding crystal phase transitions. Photoluminescence and cathodoluminescence at 10 K reveal distinct spectra corresponding to either the ZB or WZ phase. Emission above and below ~2.15 eV are associated with ZB and WZ, respectively. The characteristic WZ spectrum arises from a bound exciton and its phonon replicas, consistent with published results. The origin of emission in the ZB regime is less conclusive, but may originate from the splitting of a bound exciton by the field of an axial defect. The results presented in this thesis establish a link between NW growth, morphology, and optoelectronic properties to inform future work involving ultrathin NWs. / Thesis / Master of Applied Science (MASc) / A nanowire (NW) is a tiny rod with a length on the order of one millionth of a meter and diameter on the order of one billionth of a meter. We made gallium phosphide (GaP) NWs by stacking gallium and phosphorus atoms in a column. The NWs were separated by a constant distance. In some cases, we also added beryllium and tellurium atoms to our NWs. The addition of tellurium caused our NWs to grow into extremely sharp points, which we measured with a microscope that uses electrons instead of light. The microscope images also revealed that the arrangement of the atoms in the NW changes along its length. By detecting the light emission from the NWs, it was possible to distinguish between two unique arrangements. Overall, the small dimensions of our GaP NWs make them interesting for applications that require the emission or detection of single particles of light.

No description available.

abstract: It has been a long-standing goal to epitaxially integrate III-V alloys with Si substrates which can enable low-cost microelectronic and optoelectronic systems. Among the III-V alloys, gallium phosphide (GaP) is a strong candidate, especially for solar cells applications. Gallium phosphide with small lattice mismatch (~0.4%) to Si enables coherent/pseudomorphic epitaxial growth with little crystalline defect creation. The band offset between Si and GaP suggests that GaP can function as an electron-selective contact, and it has been theoretically shown that GaP/Si integrated solar cells have the potential to overcome the limitations of common a-Si based heterojunction (SHJ) solar cells. Despite the promising potential of GaP/Si heterojunction solar cells, there are two main obstacles to realize high performance photovoltaic devices from this structure. First, the growth of the polar material (GaP) on the non-polar material (Si) is a challenge in how to suppress the formation of structural defects, such as anti-phase domains (APD). Further, it is widely observed that the minority-carrier lifetime of the Si substrates is significantly decreased during epitaxially growth of GaP on Si. In this dissertation, two different GaP growth methods were compared and analyzed, including migration-enhanced epitaxy (MEE) and traditional molecular beam epitaxy (MBE). High quality GaP can be realized on precisely oriented (001) Si substrates by MBE growth, and the investigation of structural defect creation in the GaP/Si epitaxial structures was conducted using high resolution X-ray diffraction (HRXRD) and high resolution transmission electron microscopy (HRTEM). The mechanisms responsible for lifetime degradation were further investigated, and it was found that external fast diffusors are the origin for the degradation. Two practical approaches including the use of both a SiNx diffusion barrier layer and P-diffused layers, to suppress the Si minority-carrier lifetime degradation during GaP epitaxial growth on Si by MBE were proposed. To achieve high performance of GaP/Si solar cells, different GaP/Si structures were designed, fabricated and compared, including GaP as a hetero-emitter, GaP as a heterojunction on the rear side, inserting passivation membrane layers at the GaP/Si interface, and GaP/wet-oxide functioning as a passivation contact. A designed of a-Si free carrier-selective contact MoOx/Si/GaP solar cells demonstrated 14.1% power conversion efficiency. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2017

Ce travail de thèse porte sur les propriétés structurales, optiques et électriques de nanostructures et alliages à base de GaP pour la photonique intégrée sur silicium. Parmi les méthodes d’intégration des semi-conducteurs III-V sur Si, l’intérêt de l’approche GaP/Si est tout d’abord discuté. Une étude de la croissance et du dopage de l’AlGaP est présentée afin d’assurer le confinement optique et l’injection électrique dans les structures lasers GaP. Les difficultés d’activation des dopants n sont mises en évidence. Ensuite, les propriétés de photoluminescence des boites quantiques InGaAs/GaP sont étudiées en fonction de la température et de la densité d’excitation. Les transitions optiques mises en jeu sont identifiées comme étant des transitions indirectes de type-I avec les électrons dans les niveaux Xxy et les trous dans les niveaux HH des boites quantiques InGaAs et de type-II avec les électrons dans les niveaux Xz du GaP contraint. Malgré une modification notable de la structure électronique de ces émetteurs, une transition optique directe et type I n’est pas obtenue ce qui reste le verrou majeur pour la promotion d’émetteurs GaP sur Si. La maitrise de l’interface GaP/Si et de l’injection électrique est par ailleurs validée par la démonstration de l’électroluminescence à température ambiante d’une LED GaPN sur Si. Si l’effet laser n’est pas obtenu dans les structures lasers rubans GaP, un possible début de remplissage de la bande Гdans les QDs est discuté. Enfin, l’adéquation des lasers à l’état de l’art avec les critères d’interconnections optiques sur puce est discutée. / This PhD work focuses on the structural, optical, electrical properties of GaP-based nanostructures and alloys for integrated photonics on silicon. Amongst the integration approaches of III-V on Si, the interest of GaP/Si is firstly discussed. A study of the growth and the doping of AlGaP used as laser cladding layers (optical confinement and electrical injection) is presented. The activation complexity of n-dopants is highlighted. Then, the photoluminescence properties of InGaAs/GaP quantum dots are investigated as a function of temperature and optical density. The origin of the optical transitions involved are identified as (i) indirect type-I transition between electrons in Xxy states and holes in HH states of quantum dots InGaAs and (ii) indirect type-II with electrons in Xz states of strained GaP. Despite an effective modification in the electronic structure of these emitters, a direct type I optical transition is not demonstrated. This is the major bottleneck in the promotion of GaP based emitters on Si. This said, the control of the GaP/Si interface and electrical injection are confirmed by the demonstration of electroluminescence at room temperature on Si. If no laser effect is obtained in rib laser architectures, a possible beginning of Г band filling in QDs is discussed. Finally, the adequacy of state of the art integrated lasers with the development of on-chip optical interconnects is discussed.

This thesis reports the effects of ultrashort laser pulse irradiation of various materials. The morphology after irradiation was examined using several microscopy techniques. Emphasis was placed on the identification of crystallographic changes and the analysis of laser-induced periodic surface structures. Grooves were machined in silicon by translating the target under the focused laser beam. The resulting depths were measured as a function of pulse energy, translation speed, and number of consecutive passes, for 800 and 400nm wavelength irradiation. The wall morphology and a corrugation along the bottom of the grooves were characterized. Various polarization configurations relative to the translation direction were compared. Such characterizations are relevant for the practical application of femtosecond laser micromachining. Silicon and gallium phosphide exhibited periodic structures after irradiation using photon energies less than the bandgap energy, with periods as small as ~20% of the irradiation wavelength. The significantly sub-wavelength periodic structures had a shallow profile on silicon, appearing as fine lines or grids of protrusions and depressions. On gallium phosphide, the surface evolved into planar-like structures with a large aspect ratio, possessing crystalline centers coated with amorphous material. These investigations, along with additional experiments, would help identify the precise physical origins of the short-period structures. On silicon and germanium, the target crystal orientation was shown to affect the formation of certain morphological features. For multiple-pulse irradiation, the (100) and (111) surface orientations exhibited significantly different tendencies for large conical structure formation. A thin layer of defected material coated the conical structures, with some defects present within the periodic structures. The different crystalline orientations did not affect periodic structuring. Cross-sectional transmission electron microscopy of silicon after irradiation by single pulses revealed amorphous material and dislocations in the bulk for sufficiently high pulse fluences. On a sample consisting of a metal layer on thermally-grown oxide on silicon, a range of pulse fluences was found which removed the metal layer without observed thinning of the oxide layer. Within this fluence range, above a particular fluence substantial defects were formed in the underlying silicon. Although ultrashort pulse irradiation of materials is frequently considered to be 'damage-free', attention should be paid to sub-surface modifications not evident from surface imaging. For the drilling of holes in copper foils, the pulse duration did not strongly affect the final morphology for durations under several picoseconds. A photodiode below the foil during drilling recorded transmitted light, indicating the number of pulses required for penetration under a variety of conditions, and characterizing hole evolution during drilling. Periodic surface structuring on the walls of holes depended on the irradiation atmosphere, pulse duration, and laser polarization. These measurements provide insight into the physical processes of material modification, and for the selection of irradiation parameters in practical applications. / Thesis / Doctor of Philosophy (PhD)

L'optomécanique est la science des interactions entre la lumière et les mouvements mécaniques. Ce rapport de thèse décrit des expériences réalisées avec des microdisques fabriqué dans différents résonateurs semi-conducteurs III-V: l'Arséniure de Gallium (GaAs), l'Arséniure d'Aluminium Gallium (AlGaAs) et l'Arséniure d'Indium Phosphide (InGaP). Ces matériaux sont compatibles avec les fonctionnalités de l’optoélectronique et procurent un couplage optomécanique géant. Pour améliorer les performances des résonateurs en GaAs, nous avons développé des méthodes de traitement de surface permettant de réduire la dissipation optique par un facteur dix et ainsi d'atteindre un facteur de qualité de six millions. En plus de ces études sur le GaAs, nous avons réalisés une étude comparative des interactions optomecaniques dans des microdisques d'InGaP et d'AlGaAs, et nous avons mis en évidences leurs résonances optomécaniques. Finalement, nous avons réalisé des mesures de force avec des résonateurs en GaAs, démontrant un nouveau principe de détection basé sur notre étude de leur la trajectoire dans l'espace de phase et leur bruit de phase / Optomechanics studies the interaction between light and mechanical motion. This PhD thesis reports on optomechanical experiments carried with miniature disk resonators fabricated out of distinct III-V semiconductors: Gallium Arsenide (GaAs), Aluminium Gallium Arsenide (AlGaAs) and Indium Gallium Phosphide (InGaP). These materials are compliant with optoelectronics functionalities and provide giant optomechanical coupling. In order to boost performances of GaAs resonators, we implemented surface control techniques and obtained a ten-fold reduction of optical dissipation, attaining a Q of six million. On top of GaAs, we performed a comparative investigation of optomechanical interactions in InGaP and AlGaAs disk resonators, and demonstrated their operation as optomechanical oscillators. Finally, we carried out optomechanical force sensing experiments with GaAs resonators, analyzing a new sensing principle in light of the phase space trajectory and phase noise of the corresponding oscillators