Download or read book Magneto Optical Properties of Narrow Gap Semiconductor Nanostructures written by Dipta Saha and published by . This book was released on 2014 with total page 123 pages. Available in PDF, EPUB and Kindle. Book excerpt: The calculations of CR spectra, valence Landau suband structure, and average z component of the spins explain the differences between the CR measurements that are observed in molecular beam epitaxy (MBE) and metal organic vapor phase epitaxy (MOVPE) samples, and the higher Curie temperature in the MOVPE structures. In the OPNMR experiments on AlGaAs/GaAs MQW, the sign change of the calculated electron spin polarization agrees with the sign change of the OPNMR signal. This sign change has not been observed in bulk GaAs. The strain effect and density of states in the strained MQW are responsible for this sign change. The calculated magneto-absorption with biaxial strain effects included more accurately reproduces the experimental results of AlInSb/InSb parabolic MQW. Comparing the results with that of the AlInSb/InSb square MQW indicates that the shape of the confinement affects the magneto-absorption significantly.

Download or read book Magneto optical Properties of Narrow gap Semiconductor Heterostructures written by Xingyuan Pan and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: ABSTRACT: Next generation of semiconductor device will not only based on the charge transport properties of the carrier, but also their spin degree of freedom. In order to understand or predict how those devices work one need to understand the spin-dependent electronic structures of both bulk and low-dimensional semiconductors. We have theoretically studied the spin-dependent Landau levels for electrons or holes in bulk GaAs system and AlInSb/InSb multiple quantum wells system. We use the envelope function approximation for the electronic and magneto-optical properties of AlInSb/InSb superlattices. Our model includes the conduction electrons, heavy holes, light holes and the split-off holes for a total of 8 bands when spin is taken into account. It is a generalization of the Pidgeon-Brown model to include the wave vector dependence of the electronic states, as well as quantization of wave vector due to multiple quantum well superlattice effects. In addition, we take strain effects into account by assuming pseudomorphic growth conditions. For bulk GaAs system, we calculated the spin-dependent absorption coefficients which can be directly compared with the optically pumped NMR experiment. We show that the optically pumped NMR is a complimentary tool to traditional magneto optical absorption measurement, in the sense that optically pumped NMR is more sensitive to the light hole transitions which are very hard to resolve in the traditional magneto absorption measurement. For the AlInSb/InSb multiple quantum well system, we calculated both the magneto absorption spectra and 10 the cyclotron resonance spectra. We compare both spectra to experimental results and achieve a good agreement. This agreement assures us that our understanding of the valence band structure of the narrow gap InSb materials are correct.

Download or read book Optical Properties of Semiconductor Nanostructures written by Marcin L. Sadowski and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 443 pages. Available in PDF, EPUB and Kindle. Book excerpt: Optical methods for investigating semiconductors and the theoretical description of optical processes have always been an important part of semiconductor physics. Only the emphasis placed on different materials changes with time. Here, a large number of papers are devoted to quantum dots, presenting the theory, spectroscopic investigation and methods of producing such structures. Another major part of the book reflects the growing interest in diluted semiconductors and II-IV nanosystems in general. There are also discussions of the fascinating field of photonic crystals. `Classical' low dimensional systems, such as GsAs/GaAlAs quantum wells and heterostructures, still make up a significant part of the results presented, and they also serve as model systems for new phenomena. New materials are being sought, and new experimental techniques are coming on stream, in particular the combination of different spectroscopic modalities.

Download or read book Magneto optical Properties of II VI Semiconductor Colloidal Nanostructures written by Feng Liu and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Narrow Gap Semiconductors written by Junichiro Kono and published by CRC Press. This book was released on 2006-05-25 with total page 636 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume forms a solid presentation in several important areas of NGS research, including materials, growth and characterization, fundamental physical phenomena, and devices and applications. It examines the novel material of InAs and its related alloys, heterostructures, and nanostructures as well as more traditional NGS materials such as InSb, PbTe, and HgCdTe. Several chapters cover carbon nanotubes and spintronics, along with spin-orbit coupling, nonparabolicity, and large g-factors. The book also deals with the physics and applications of low-energy phenomena at the infrared and terahertz ranges.

Download or read book Magneto Optical Properties of Hybrid Magnetic Material Semiconductor Nanostructures written by and published by . This book was released on 2003 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Calculations were performed of the formation energies of transition metal carbides and silicides in order to evaluate the thermodynamic limitations to incorporation of these elements as dopants in Silicon carbide. The prospects of SiC as a host for dilute magnetic semiconductor applications by doping with Cr and Mn were evaluated. Calculations were performed for MnN and Mn3N2 compounds and a model developed for explaining their anti ferromagnetic order in terms of exchange interactions between near neighbors. Densities of states calculations of these materials were used to interpret spin-polarized scanning tunneling microscopy data. Calculations were performed for FeN in zincblende and rocksalt structure to compare their relative stability and magnetic properties. Calculations of the preference for ferro or anti ferromagnetic coupling were performed for GdN. Program development work on magneto- optics and methods beyond LDA was initiated.

Download or read book Magneto optical Properties of II VI Semiconductor Colloidal Nanostructure written by and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Magneto optical Properties of Semiconductor Heterostructures written by Sung-Ryul Yang and published by . This book was released on 1986 with total page 276 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Optical Properties of Semiconductor Nanostructures in Magnetic Field written by Michal Grochol and published by . This book was released on 2007 with total page 151 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Magneto optical Properties of Semiconductor Nanocrystals in Glass written by Gang Qiang and published by . This book was released on 2022 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Narrow Gap Semiconductors 1992 Proceedings of the 6th INT Conference University of Southampton UK 19 23 July 1992 written by Richard Anthony Stradling and published by CRC Press. This book was released on 1993 with total page 480 pages. Available in PDF, EPUB and Kindle. Book excerpt: The papers presented here first appeared in Semiconductor Science and Technology (1993, Volume 8, Number 1S), a journal from Institute of Physics Publishing

Download or read book Magneto Optical Properties of a Semiconductor Dot Or Shell written by 鍾佳民 and published by . This book was released on 2007 with total page 55 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Semiconductor Nanostructures written by Dieter Bimberg and published by Springer Science & Business Media. This book was released on 2008-06-03 with total page 369 pages. Available in PDF, EPUB and Kindle. Book excerpt: Reducing the size of a coherently grown semiconductor cluster in all three directions of space to a value below the de Broglie wavelength of a charge carrier leads to complete quantization of the energy levels, density of states, etc. Such “quantum dots” are more similar to giant atoms in a dielectric cage than to classical solids or semiconductors showing a dispersion of energy as a function of wavevector. Their electronic and optical properties depend strongly on their size and shape, i.e. on their geometry. By designing the geometry by controlling the growth of QDs, absolutely novel possibilities for material design leading to novel devices are opened. This multiauthor book written by world-wide recognized leaders of their particular fields and edited by the recipient of the Max-Born Award and Medal 2006 Professor Dieter Bimberg reports on the state of the art of the growing of quantum dots, the theory of self-organised growth, the theory of electronic and excitonic states, optical properties and transport in a variety of materials. It covers the subject from the early work beginning of the 1990s up to 2006. The topics addressed in the book are the focus of research in all leading semiconductor and optoelectronic device laboratories of the world.

Download or read book Optical Properties of Semiconductor Nanocrystals written by S. V. Gaponenko and published by Cambridge University Press. This book was released on 1998-10-28 with total page 263 pages. Available in PDF, EPUB and Kindle. Book excerpt: Examines the optical properties of low-dimensional semiconductor structures, a hot research area - for graduate students and researchers.

Download or read book Magnetooptical properties of dilute nitride nanowires written by Mattias Jansson and published by Linköping University Electronic Press. This book was released on 2020-06-18 with total page 77 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanostructured III-V semiconductors have emerged as one of the most promising materials systems for future optoelectronic applications. While planar III-V compounds are already at the center of the ongoing lighting revolution, where older light sources are replaced by modern white light LEDs, fabricating such materials in novel architectures, such as nanowires and quantum dots, creates new possibilities for optoelectronic applications. Not only do nanoscale structures allow the optically active III-V materials to be integrated with silicon microelectronics, but they also give rise to new fascinating properties inherent to the nanoscale. One of the key parameters considered when selecting materials for applications in light-emitting and photovoltaic devices is the band gap energy. While alloying of conventional III-V materials provides a certain degree of band gap tunability, a significantly enhanced possibility of band gap engineering is offered by so-called dilute nitrides, where incorporation of a small percentage of nitrogen into III-V compounds causes a dramatic down-shift of the conduction band edge. In addition, nitrogen-induced splitting of the conduction band in dilute nitrides can be utilized in intermediate band solar cells, belonging to the next generation of photovoltaic devices. For any material to be viable for optoelectronic applications, detailed knowledge of the electronic structure of the material, as well as a good understanding of carrier recombination processes is vital. For example, alloying may not only cause changes in the electronic structure but can also induce disorder. Disorder-induced potential fluctuations may alter charge carrier and exciton dynamics, and may even induce quantum confinement. Moreover, various defects in the material may introduce detrimental non-radiative (NR) states in the band gap deteriorating radiative efficiency. It is evident that, due to their different growth mechanisms, such properties could be markedly different in nanowires as compared to their planar counterparts. In this thesis, I aim to describe the electronic structure of dilute nitride nanowires, and its effects on the optical properties. Firstly, we investigate the electronic structure, and the structural and optical properties of novel GaNAsP nanowires, with a particular focus on the dominant recombination channels in the material. Secondly, we show how short-range fluctuations in the nitrogen content lead to the formation of quantum dots in dilute nitride nanowires, and investigate their electronic structure. Finally, we investigate the combined charge carrier and exciton dynamics of the quantum dots and effects of defects in their surroundings. Before considering individual sources of NR recombination, it is instructive to investigate the overall effects of nitrogen incorporation on the structural properties of the nanowires. In Paper I, we show that nitrogen incorporation up to 0.16% in Ga(N)AsP nanowires does not affect the overall structural quality of the material, nor does nitrogen degrade the good compositional uniformity of the nanowires. It is evident from our studies, however, that nitrogen incorporation has a strong and complex effect on recombination processes. We first show that nitrogen incorporation in GaNAsP nanowires reduces the NR recombination at room temperature as compared to the nitrogen-free nanowires (Paper I). This is in stark contrast to dilute nitride epilayers, where nitrogen incorporation enhances NR recombination. The reason for this difference is that in nanowires the surface recombination, rather than recombination via point defects, is the dominant NR recombination mechanism. We suggest that the nitrogen-induced suppression of the NR surface recombination in the nanowires is due to nitridation of the nanowire surface. Another NR recombination channel common in III-V nanowires is caused by the presence of structural defects, such as rotational twin planes and stacking faults. Interestingly, while nitrogen incorporation does not appear to affect the density of such structural defects, increasing nitrogen incorporation reduces the NR recombination via the structural defects (Paper II). This is explained by competing trapping of excited carriers/excitons to the localized states characteristic to dilute nitrides, and at nitrogen-induced NR defects. This effect is, however, only present at cryogenic temperatures, while at room temperature the NR recombination via the structural defects is not the dominant recombination channel. Importance of point defects in carrier recombination is highlighted in Paper III. Using the optically detected magnetic resonance technique, we show that gallium vacancies (VGa) that are formed within the nanowire volume act as efficient NR recombination centers, degrading optical efficiency of the Ga(N)AsP-based nanowires. Interestingly, while the defect formation is promoted by nitrogen incorporation, it is also readily present in ternary GaAsP nanowires. This contrasts with previous studies on planar structures, where VGa was not formed in the absence of nitrogen, unless subjected to irradiation by high-energy particles or heavy n-type doping. This, again, highlights how the defect formation is strikingly different in nanowires as compared to planar structures, likely due to the different growth processes. Potential fluctuations in the conduction band, caused by non-uniformity of the nitrogen incorporation, is characteristic to dilute nitrides and is known to cause exciton/carrier localization. We find that in dilute nitride nanowires, such fluctuations at the short range cause three-dimensional quantum confinement of excitons, resulting in optically active quantum dots with spectrally ultranarrow and highly polarized emission lines (Paper IV). A careful investigation of such quantum dots reveals that their properties are strongly dependent on the host material (Papers V, VI). While the principal quantization axis of the quantum dots formed in the ternary GaNAs nanowires is preferably oriented along the nanowire axis (Paper V), it switches to the direction perpendicular to the nanowire axis in the quaternary GaNAsP nanowires (Paper VI). Another aspect illustrating the influence of the host material on the quantum-dot properties is the electronic character of the captured hole. In both alloys, we show coexistence of quantum dots where the captured holes are of either a pure heavy-hole character or a mixed light-hole and heavy-hole character. In the GaNAs quantum dots, the main cause of the light- and heavy-hole splitting is uniaxial tensile strain induced by a combination of lattice mismatch with the nanowire core and local alloy fluctuations (Paper V). In the GaNAsP quantum dots, however, we suggest that the main mechanism for the light- and heavy-hole splitting is local fluctuations in the P/As ratio (Paper VI). Using time correlation single-photon counting, we show that the quantum dots in these dilute nitride nanowires behave as single photon emitters (Paper VI), confirming the three-dimensional quantum confinement of the emitters. Finally, since the quantum dots are formed by fluctuations mainly in the conduction band, only electrons are preferentially captured in the 0D confinement potential, whereas holes are expected to be mainly localized through the Coulomb interaction once an electron is captured by the quantum dot. In Paper VII, we investigate this rather peculiar capture mechanism, which we show to lead to unipolar, negative charging of the quantum dot. Moreover, we demonstrate that carrier capture by some quantum dots is strongly affected by the presence of defects in their local surroundings, which further alters the charge state of the quantum dot, where formation of the negatively charged exciton is promoted at the expense of its neutral counterpart. This underlines that the local surroundings of the quantum dots may greatly affect their properties and illustrates a possible way to exploit the defects for charge engineering of the quantum dots. In summary, in this thesis work, we identify several important non-radiative recombination processes in dilute nitride nanowires that can undermine the potential of these novel nanostructures for future optoelectronic applications. The gained knowledge could be found useful for designing strategies to mitigate these harmful processes, thereby improving the efficiency of future light-emitting and photovoltaic devices based on these nanowires. Furthermore, we uncover a set of optically bright quantum dot single-photon emitters embedded in the dilute nitride nanowires, and reveal their unusual electronic structure with strikingly different confinement potentials between electrons and holes. Our findings open a new pathway for charge engineering of the quantum dots in nanowires, attractive for applications in e.g. quantum computation and optical switching.

Download or read book Optical Properties of Metal Oxide Nanostructures written by Vijay Kumar and published by Springer Nature. This book was released on 2023-10-25 with total page 515 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book highlights the optical properties of metal oxides at both the fundamental and applied level and their use in various applications. The book offers a basic understanding of the optical properties and related spectroscopic techniques essential for anyone interested in learning about metal oxide nanostructures. This is partly due to the fact that optical properties are closely associated with other properties and functionalities (e.g., electronic, magnetic, and thermal), which are of essential significance to many technological applications, such as optical data communications, imaging, lighting, and displays, life sciences, health care, security, and safety. The book also highlights the fundamentals and systematic developments in various optical techniques to achieve better characterization, cost-effective, user-friendly approaches, and most importantly, state-of-the-art developing methodologies for various scientific and technological applications. It provides an adequate understanding of the imposed limitations and highlights the prospects and challenges associated with optical analytical methods to achieve the desired performance in targeted applications.

Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 704 pages. Available in PDF, EPUB and Kindle. Book excerpt: