90 research outputs found
Demonstration of Forward Inter-band Tunneling in GaN by Polarization Engineering
We report on the design, fabrication, and characterization of GaN interband
tunnel junction showing forward tunneling characteristics. We have achieved
very high forward tunneling currents (153 mA/cm2 at 10 mV, and 17.7 A/cm2 peak
current) in polarization-engineered GaN/InGaN/GaN heterojunction diodes grown
by plasma assisted molecular beam epitaxy. We also report the observation of
repeatable negative differential resistance in interband III-Nitride tunnel
junctions, with peak-valley current ratio (PVCR) of 4 at room temperature. The
forward current density achieved in this work meets the typical current drive
requirements of a multi-junction solar cell.Comment: 3 figure
The Dawn of Photonic Crystals: An Avenue for Optical Computing
In this chapter, a new paradigm is developed for optical computation using photonic crystals. As photonic crystals are the most sophisticated optical materials to date, information processing using this structure is one of the most sought-after technologies in photonics. While the semiconductor industry is striving hard to increase the microprocessors’ processing power, it is certain that the trend would not last forever as against Moore’s prediction. At this juncture, photonics technologies have to compete with the upcoming quantum computing technology to emerge as a promising successor for semiconductor microprocessors. This chapter is devoted to the introduction of photonic crystals as the workhorse for an all-optical computational system with a myriad of logic gates, memory units, and networks which can be constructed using these structures
Electrical Properties of Atomic Layer Deposited Aluminum Oxide on Gallium Nitride
We report on our investigation of the electrical properties of
metal/Al2O3/GaN metal-insulator-semiconductor (MIS) capacitors. We determined
the conduction band offset and interface charge density of the alumina/GaN
interface by analyzing capacitance-voltage characteristics of atomic layer
deposited Al2O3 films on GaN substrates. The conduction band offset at the
Al2O3/GaN interface was calculated to be 2.13 eV, in agreement with theoretical
predications. A non-zero field of 0.93 MV/cm in the oxide under flat-band
conditions in the GaN was inferred, which we attribute to a fixed net positive
charge density of magnitude 4.60x1012 cm-2 at the Al2O3/GaN interface. We
provide hypotheses to explain the origin of this charge by analyzing the energy
band line-up.Comment: 8 pages, 4 figures, Applied Physics Letter
An Assessment of Onshore and Offshore Wind Energy Potential in India Using Moth Flame Optimization
Wind energy is one of the supremely renewable energy sources and has been widely established worldwide. Due to strong seasonal variations in the wind resource, accurate predictions of wind resource assessment and appropriate wind speed distribution models (for any location) are the significant facets for planning and commissioning wind farms. In this work, the wind characteristics and wind potential assessment of onshore, offshore, and nearshore locations of India—particularly Kayathar in Tamilnadu, the Gulf of Khambhat, and Jafrabad in Gujarat—are statistically analyzed with wind distribution methods. Further, the resource assessments are carried out using Weibull, Rayleigh, gamma, Nakagami, generalized extreme value (GEV), lognormal, inverse Gaussian, Rician, Birnbaum–Sandras, and Bimodal–Weibull distribution methods. Additionally, the advent of artificial intelligence and soft computing techniques with the moth flame optimization (MFO) method leads to superior results in solving complex problems and parameter estimations. The data analytics are carried out in the MATLAB platform, with in-house coding developed for MFO parameters estimated through optimization and other wind distribution parameters using the maximum likelihood method. The observed outcomes show that the MFO method performed well on parameter estimation. Correspondingly, wind power generation was shown to peak at the South West Monsoon periods from June to September, with mean wind speeds ranging from 9 to 12 m/s. Furthermore, the wind speed distribution method of mixed Weibull, Nakagami, and Rician methods performed well in calculating potential assessments for the targeted locations. Likewise, the Gulf of Khambhat (offshore) area has steady wind speeds ranging from 7 to 10 m/s with less turbulence intensity and the highest wind power density of 431 watts/m2. The proposed optimization method proves its potential for accurate assessment of Indian wind conditions in selected locations.publishedVersio
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