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This paper describes a high step-down unregulated, fixed-ratio DC-DC converter (DCX) based on the dual active bridge (DAB) power stage operating at high switching frequency using enhancement-mode Gallium-Nitride-on-Silicon (GaN) transistors. The DAB power stage design as well as a comparison of losses using GaN and silicon MOS devices is based on a detailed state-plane analysis of resonant transitions...
In many communications applications semiconductor devices operate in a pulsed mode, where rapid temperature transients are continuously experienced within the die. We proposed a novel junction-level cooling technology where a metallic phase change material (PCM) was embedded in close proximity to the active transistor channels without interfering with the device's electrical response. Here we present...
A common approach for converting sunlight to electricity at a low cost is either to achieve high conversion efficiencies and/or by using low-cost systems. High solar energy conversion efficiency by using photovoltaic devices has been achieved by concentrating sunlight on a multi-junction monolithically stacked solar cell. The process of manufacturing monolithically stacked solar cells is complex and...
This paper presents an analysis of the noise spectra of GaAs and GaN Schottky barrier diodes (SBD) operating under static and time varying conditions. The noise spectra obtained from Monte Carlo simulations (MC) of the SBDs show two resonances in the terahertz frequency region that are analyzed as a function of the SBD structure and working conditions. MC simulations are compared with published analytical...
The temperature impact on the Ohmic contact to Gallium Nitride (GaN) device properties is investigated in the range of 25°C to 300°C by means of the Transmission Line Method (TLM) technique. This study is centered in two kinds of Ohmic contacts: Implanted N+ GaN and heterojunction AlGaN/GaN contacts. For N+ contact resistance behavior is explained in terms of the field-effect or thermionic field effect...
The work presented here aims to reduce the cost of multijunction solar cell technology by developing ways to manufacture them on cheap substrates such as silicon. In particular, our main objective is the growth of III-V semiconductors on silicon substrates for photovoltaic applications. The goal is to create a GaAsP/Si virtual substrates onto which other III-V cells could be integrated with an interesting...
A hybrid III-V silicon evanescent laser with sidewalled gratings as the feedback element, and having 60% waveguide confinement is proposed. The device is fabricated using e-beam lithography, and low-temperature plasma assisted direct bonding.
This paper shows improved phase-noise performance of MEMS oscillators when the sustaining amplifier operates a lateral bulk acoustic wave AlN-on-Si resonator in the nonlinear regime. An empirical exponential-series-based model that closely describes the phase noise in nonlinearity is presented, reflecting the increased resonator filter order and the reduced amplifier flicker-noise contribution. An...
The properties of a new class of electromechanical resonators based on GaN are presented. By using the two-dimensional electron gas (2-DEG) present at the AlGaN/GaN interface and the piezoelectric properties of this heterostructure, we use the R-HEMT (Resonant High Electron Mobility Transistor) as an active piezoelectric transducer up to 5MHz. In addition to the amplification effect of piezoelectric...
Progress in the synthesis and properties of crystalline semiconductor core optical fibers is reviewed. This new class of optical fibers may significantly advance the fields of nonlinear fiber optics and infrared power delivery.
We report on the epitaxial growth, fabrication, and characterization of full-color InGaN/GaN dot-in-a-wire nanoscale LEDs on Si(111), which can exhibit an internal quantum efficiency of ~ 45% and negligible saturation up to ~ 300 A/cm2.
Heterogeneous integration of III-V microlasers on silicon is discussed as a promising scheme for photonic-electronic convergence. The typical performances of an optical interconnect circuit are evaluated and two types of microlasers are proposed and compared.
A comparison of the conversion efficiency from optical power to electrical power for three common material homojunction photovoltaic micro-cells was performed. The device widths were varied as a function of incident wavelength such that optimum power conversions were determined whilst under illumination of monochromatic light. GaAs is the most effective material as optimum devices can be fabricated...
The wafer direct bonding technology enables one to integrate dissimilar crystals like magneto-optic garnet on Si and III-V semiconductors. Optical nonreciprocal devices are fabricated based on the wafer bonding technology.
Hybrid integration of III-V compound semiconductors onto silicon-on-insulator (SOI) substrate is discussed from material, device and application perspective. Recent progress in integration technology and device optimization is reviewed.
We characterize the microwave loss in coplanar waveguides (CPWs) on AlGaN/GaN HEMT buffer layers on high-resistivity silicon (HR-Si) substrates, up to 110 GHz. To our knowledge, this is the first broadband characterization of CPWs on GaN-on-Si. Conventional CPWs on commercially available AlGaN/GaN on HR-Si HEMT layers show a loss as low as 0.8 dB/mm at 110 GHz. Losses are further reduced by etching...
In this article, Gallium nitride (GaN) cantilevers integrated with AlGaN/GaN high electron mobility transistors (HEMTs) are fabricated with a GaN-on-silicon platform, which is fully compatible with the standard HEMTs fabrication process. A type of micro-bending test was used to characterize the piezoresponse of AlGaN/GaN HEMT on the GaN cantilever. The modulation capability of the AlGaN/GaN heterostructures...
Integrated components for optical networks-on-chip, including III-V microdisk lasers, photodetectors, and wavelength selective circuits, are all demonstrated using a complementary metal-oxide-semiconductor (CMOS) compatible III-V/silicon-oninsulator integration technology at 200mm wafer scale.
We demonstrate efficient photodetectors on top of a laser epitaxial structure completely fabricated using 200 mm wafer scale III-V/SOI technology enabling very dense integration of lasers and detectors for optical interconnect circuits.
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