Use of Nanostructures for High Brightness Light-Emitting Diodes

Abstract

Light-emitting diodes or LEDs are expected to play a major role in efforts to utilize less energy for lighting applications due to their high efficiency, long operating life, and other ''green'' characteristics. The history of LEDs began in the 1960s. Since that time, the performance has increased exponentially while the cost has decreased dramatically. LEDs dominate the market for monochromatic displays and indicators, and are slated to provide an increasing share of the white light market. During the last decade, advances in efficiency have been obtained partly as a result of the use of nanotechnology. LEDs and lasers provided some of the first applications for quantum-well structures with nm dimensions. Future advances will almost certainly be linked to advances in the use of quantum wire and quantum dot structures. They appear to offer attractive new alternatives for single-junction white light generation. The use of self-assembled structures also offers the promise of allowing the fabrication of high efficiency devices in highly defected materials, such as those grown on less expensive substrates. This chapter reviews the basic aspects of LED devices and materials, with a focus on the AlGaInP system for red and yellow emitters and AlGaInN for blue, green, and white emitters, all grown by the organometallic vapor phase epitaxial technique. The focus is on the present and future use of nanotechnology for lighting applications.

Perspective of Waste to Energy and Fuel with Negative Emission Potential: Smart Environmental and Techno-economic Analysis

“…Costs vary from technology to technology attributing to the site-specific waste/feedstock characteristics and market conditions, unique design and operating parameters of each process reactor, particular construction requirements, and variations in material and equipment costs. Considering a waste conversion process with a capacity of 15 MW output, the capital costs for the typical conversion technologies range from 7000 to 10 000 USD/kW for direct combustion, from 8000 to 11 500 USD/kW for pyrolysis, and from 7500 to 11 000 USD/kW for conventional gasification . For interested readers, the investment and operating costs of the waste-to-bioenergy/biochar facilities reported by several researchers have been summarized in Table .…”

Characterization Parameters of (InGaN/InGaN) and (InGaN/GaN) Quantum Well Laser Diode

“…A wide spectrum of bandgap bowing parameters has been obtained for ternary nitride alloys due to differences in growth and measurement conditions. For layers with low mole fraction of the alloy element (x<0.2), we employ the following room temperature relations for the direct bandgap (Stringfellow and Craford, 1997;Nakamura and Fasol, 1997).…”

Advantage of dual wavelength light-emitting diodes with dip-shaped quantum wells

“…where E g (InN), E g (AlN) and E g (GaN) are the bandgap energies of InN, AlN and GaN, with values of 0.78, 6.25 and 3.51 eV, respectively [14]. The internal absorption within the LED device is assumed to be 500 m 1 and the operating temperature is assumed to be 300 K. To simplify the simulation, the light extraction efficiency is assumed to be 0.78.…”