Papers by Keyword: Wide Band Gap

Abstract: To minimize interfacial power losses, thin layers of NiO, a p-type oxide semiconductor, are inserted between the active organic layer, poly(3-hexylthiophene) (P3HT) [6,6]-phenyl-C61 butyric acid methyl ester (PCBM), and the ITO (tin-doped indium oxide) anode of bulk-heterojunction ITO/P3HT:PCBM/Al solar cells. The interfacial NiO layer is deposited by radio frequency (RF) magnetron sputtering deposition directly onto cleaned ITO, and the active layer is subsequently deposited by spin-coating. Insertion of the NiO layer affords cell power conversion efficiencies as high as 2.5% and enhances the fill factor to 56% and the open-circuit voltage (Voc) to 605 mV versus ones without NiO buffering layer control device. The value of such hole-transporting/electron-blocking interfacial layers is clearly demonstrated and should be applicable to other organic photovoltaics.

Abstract: The performance of a 12kV planar Clustered Insulated Gate Bipolar Transistor (CIGBT) is compared to an equivalent IGBT in 4H-SiC through extensive 2D numerical simulations. The CIGBT shows 40% reduction in Eoff-Vce(sat) trade off losses with a short circuit endurance time of more than 10µs.

Abstract: Because of strong synergy with information technology, visible light imaging, and solar cell businesses, most of the devices for medium and high voltage power electronics are based on silicon in year 2009 [1]. Still we know, for more than 50 years, that “harder” semiconductors, exhibiting higher breakdown electric field, would be preferable [2]. On the way towards the development of such new materials, the road is very narrow between so many intricate scientific and technical obstacles. After 50 years of SiC technology development, a first generation of reliable Schottky rectifiers is now available [3,4], but it will take time to turn it into a profitable business. Despite of very important progress over the past 15 years, it is not yet clear whether there will ever be any reliable high voltage switching device based on SiC MOS [5-7]. Vertical JFET have recently appeared as realistic alternative solutions [9-12]. Hetero-epitaxial GaN materials on sapphire or silicon substrate may appear as competitors to SiC. Progress on the crystal growth of Diamond, Aluminum Nitride [8] and Boron Nitrides for electronics is on the way, but there is no convincing solution identified yet for the basic doping problems. Regarding the more ionic II-VI or I-VII semiconductors, very few people still believe that they can play a role inside future device structures for power electronics.

Abstract: A broad range of II-VI materials has been investigated in order to produce light in the full visible range for optoelectronic applications. The present investigation was carried out for the spectroscopic analysis and synthesis of wide band gap cadmium sulfide nanoparticles. Large-band gap semiconductors have the added advantage in that; they can support higher electric field before breaking down, which means that they can be used for high-power electronic devices.Synthesis has been carried out using colloidal synthesis technique at low temperature. The size, stabilization and optical properties were studied using UV-vis Spectrophotometer and Spectroflourometer. Further, the structural studies of synthesized powder were carried out using X-ray diffraction technique; which also confirms the formation of desired product. The capping ligand and the impurities present in the sample were characterized by Fourier transform infra red spectroscopy. Synthesized CdS powder dispersed in aqueous media gave the value of 193 nm for the onset wavelength using UV-vis spectrophotometer, which is significantly blue-shifted compared to bulk CdS and shows the quantum confinement effect. From the onset wavelength the radius of CdS quantum dot calculated using the Brus equation was found to be ca. 0.7 nm.

Abstract: We have designed, simulated, fabricated, and characterized high-voltage 4H-SiC p-channel DMOS-IGBTs on 20 kV blocking layers for use as the next generation of power switching devices. These p-IGBTs exhibit significant conductivity modulation in the drift layer. The maximum currents of the experimental p-channel IGBTs are 1.2x and 2.1x higher than the ideal 20 kV n-channel DMOSFETs at room temperature and 175°C, respectively.

Abstract: This chapter serves as an introduction to the chapters on III-nitrides in this book. It gives a brief review of the development of relevant III-nitride materials for light emitters since the late 1960´s, when single crystalline GaN layers grown on sapphire were first demonstrated. The first wave of scientific work died out in the late 1970´s, since low-ohmic p-GaN could not be made at the time. After another 10 years several important breakthroughs were made, using the technology of metal organic vapor phase epitaxy (MOVPE). Smooth thin epilayers could be made, and ways to dope the materials n-type as well as p-type were invented. In the period 1986-1997 high brightness violet and blue double heterostructure (DH) LEDs, narrow quantum well (QW) LEDs, and QW based violet laser diodes with a long operating lifetime of 10000 hours were demonstrated, mainly by Japanese groups. Since then the development efforts have spread worldwide, and a large spectrum of novel applications based on nitride emitters are already in practical use. Perhaps the most important one is the future possibility of using nitride LEDs for general lighting purposes.

Abstract: Cu(In,Ga)3Se5 films were deposited on soda-lime glass substrate by three-stage co-evaporation process. In the film, the band gap increased as the Cu content decreased and also as the Ga content increased. The grain size became smaller as the Ga content increased. In the Cu1.29(In1-xGax)3Se5 system, the maximum hole concentration was 1x1015 /cm3 when the Ga content was 0.5 and its band gap was 1.45 eV. Comparing the conventional CIGS solar cell with Cu0.8(In0.7Ga0.3)Se2 film, the series resistance is too large, indicating that further p-type doping in the Cu(In,Ga)3Se5 film is necessary to improve cell efficiency for the top cell application in CIGS tandem solar cells.