Kingsley Ogudo | University of South Africa (original) (raw)

Papers by Kingsley Ogudo

In this article, we discuss the emission of visible light (400–900 nm) by a monolithically integr... more In this article, we discuss the emission of visible light (400–900 nm) by a monolithically integrated silicon p-n junction under reverse bias. Silicon light emitting devices (Si-LEDs) could be designed and realized utilizing the standard complementary metal oxide semiconductor (CMOS) technology. Increased electroluminescence from the three-terminal MOS-like structure is observed, with the approach of carrier energy and momentum engineering design. Because Si-LEDs, waveguides, and photodetectors (Si) can be integrated on a single chip, a small microphotonic system could be realized in the CMOS integrated circuitry standard platform. The results can be substantially utilized for realizing a complete on-chip optical link.

Silicon Photonics is an emerging field of research and technology, where nano-silicon can play a ... more Silicon Photonics is an emerging field of research and technology, where nano-silicon can play a fundamental role.
Visible light emitted from reverse-biased p-n junctions at highly localized regions, where avalanche breakdown occurs,
can be used to realize a visible electro-optical sources in silicon by means of light-emitting diodes (Si-LEDs) is reviewed
by characterizing the spectral distribution. Regarding applications, a monolithic optoelectronic integrated circuit (OEIC)
for on-chip optical interconnection based on standard CMOS technology is discussed. Although there are some of the
present challenges with regard to the realization of suitable electro-optical elements for diverse integrated circuit
applications, the type of silicon light source can be further developed into be a Si-based optical short-distance on-chip
optical interconnect applications.
Keywords: Silicon, optoelectronics, micro-optical devices, electro-optical modulation, PN junction.

In this paper, we describe the fabrication, using standard silicon processing techniques, of sili... more In this paper, we describe the fabrication, using standard silicon processing techniques,
of silicon light-emitting device that emit photons for future electro-optic silicon monolithic
integration on the CMOS platform.
OCIS codes: (130.3120) Integrated optics devices; (130.3990) Micro-optical devices; (130.5990) Semiconductors

Graded junction, carrier energy and momentum engineering concepts have been utilized to realize a... more Graded junction, carrier energy and momentum engineering concepts have been utilized to realize a high intensity 100 nW 5GHz Silicon Avalanche based LED (Si Av LED). A silicon 0.35 micron RF bi-polar process was used as design and processing technology.

Micron dimensioned on-chip optical links of 50 micron length, utilizing 650 -850 nm propagation w... more Micron dimensioned on-chip optical links of 50 micron length, utilizing 650 -850 nm propagation wavelength, have been realized in a Si Ge bipolar process. Key design strategies is the utilization of high speed avalanche based Si light emitting devices (Si Av LEds) in combination with silicon nitride based wave guides and high speeds Si Ge based optical detectors. The optical source, waveguide and detector were all integrated on the same chip. TEOS densification strategies and state of the art Si-Ge bipolar technology were further used as key design strategies. Best performances show up to 25 GHz RF carrier modulation and -40dBm total optical link budget loss with a power consumption of only 0.1 mW per GHz bandwidth. Improvement possibilities still exist. The process used is in regular production. The technology is particularly suitable for application as optical interconnects utilizing low loss, side surface, waveguide to optical fibre coupling.

This paper discusses the simulation, development and potential application of Si LEDs in pre-spec... more This paper discusses the simulation, development and potential application of Si LEDs in pre-specified complementary metal oxide semiconductors (CMOS) integrated circuit structures in the wavelength range of 450nm - 750nm. A MONTE CARLO simulation technique was developed in which the optical wave propagation phenomena as relevant in CMOS structures were continuously updated as the optical ray progresses through the structure. Refractive index of the material, layers thickness and structure curvatures were all incorporated as ray propagation parameters. By using a multi-ray simulation approach, the overall propagation phenomena wrt refraction, reflection, scattering, and intensities could be evaluated in globular context in any complex CMOS integrated circuit structure in a progressive way. MATLAB software was used as a mathematical capable and programmable language to develop the dedicated software evaluation tool. Subsequently, some first iteration, conceptual, applications of MOEMS structures are demonstrated as implemented in Si CMOS integrated circuitry, utilizing Si InAva LEDs and silicon detectors.

The utilization of Organic Light Emitting Diodes (OLEDs) and Si Avalanche LEDs emitting at 0.45 -... more The utilization of Organic Light Emitting Diodes (OLEDs) and Si Avalanche LEDs emitting at 0.45 - 0.75 micron enable the development of high speed all -Silicon CMOS based optical communication systems without the incorporation of materials such as Ge or III-V components. The development of low loss and high curvature optical waveguides in CMOS technology at these wavelengths, however, offers major challenges. Advanced optical simulation software was hence used in order to develop effective CMOS based waveguides, using CMOS materials characteristics, processing parameters, and the spectral characteristics of CMOS Av LEDs. The analyses show that both silicon nitride and Si oxi-nitride offer good viability for developing such waveguides, utilizing 0.2 to 1.5 micron wide CMOS over-layer as well as trench-based technology. Particularly, trench based technology are very attractive, since the optical sources can then be integrated with silicon avalanche based LEDs with trench-based waveguides on the same plane with standard CMOS processing procedures. Effective single mode wave-guiding with calculated loss characteristics of 0.65 dB.cm-1 and modal dispersion characteristics of 0.2 ps.cm-1 and with a bandwidth-length product of higher than 100 GHz-cm are predicted.

This paper analyzes the optical propagation and refraction phenomena in various complementary met... more This paper analyzes the optical propagation and refraction phenomena in various complementary metal-oxide-semiconductor (CMOS) structures at 750 nm wavelength. Operation at these wavelengths offers the potential realizations of small microphotonic systems and micro-optoelectro-mechanical systems (MOEMS) in CMOS integrated circuitry, since Si-based optical sources, waveguides, and silicon (Si) detectors can all be integrated on a single chip. It could also increase the optical coupling efficiencies to external optical fibers. With the help of Monte Carlo and RSoft BeamPROP simulations, we demonstrate achievements with regard to optimizing vertical emission, focusing, refraction, splitting and wave guiding in 0.35 to 1.2 μm CMOS technology at 750 nm wavelength. The material properties, refractive indices, and thicknesses of various CMOS over-layers were incorporated in the simulations and analyses. The analyses show that both Si nitride and Si oxi-nitride offer good viability for developing such waveguides. Effective single-mode wave-guiding with calculated loss characteristics of 0.65 dB · cm −1 , with modal dispersion characteristics of less than 0.2 ps · cm −1 and with a bandwidth-length product of higher than 100 GHz-cm seems possible. A first iteration realization of an optical link is demonstrated, utilizing specially designed avalanche-based Si-LEDs and a specially designed first iteration CMOS waveguide. Potential applications of avalanche-based Si LEDs into microphotonic systems and MOEMS are furthermore proposed and highlighted.