Quantum wells optical properties

C2.1 GalnN quantum wells composition pulling effect C2.2 GalnN quantum wells microstructure C2.3 GalnN quantum wells optical properties C2.4 GalnN quantum wells effect of phase separation on lasing... 

As is to be expected, inherent disorder has an effect on electronic and optical properties of amorphous semiconductors providing for distinct differences between them and the crystalline semiconductors. The inherent disorder provides for localized as well as nonlocalized states within the same band such that a critical energy, can be defined by distinguishing the two types of states (4). At E = E, the mean free path of the electron is on the order of the interatomic distance and the wave function fluctuates randomly such that the quantum number, k, is no longer vaHd. For E < E the wave functions are localized and for E > E they are nonlocalized. For E > E the motion of the electron is diffusive and the extended state mobiHty is approximately 10 cm /sV. For U <, conduction takes place by hopping from one localized site to the next. Hence, at U =, )J. goes through a... 

In photoluminescence one measures physical and chemical properties of materials by using photons to induce excited electronic states in the material system and analyzing the optical emission as these states relax. Typically, light is directed onto the sample for excitation, and the emitted luminescence is collected by a lens and passed through an optical spectrometer onto a photodetector. The spectral distribution and time dependence of the emission are related to electronic transition probabilities within the sample, and can be used to provide qualitative and, sometimes, quantitative information about chemical composition, structure (bonding, disorder, interfaces, quantum wells), impurities, kinetic processes, and energy transfer. 

Structural and optical properties of luGaN/GaN triangularshaped quantum wells grown by metalorganic chemical vapor depostion... 

The creation of nanoscale sandwiches of compound semiconductor heterostructures, with gradients of chemical composition that are precisely sculpted, could produce quantum wells with appropriate properties. One can eventually think of a combined device that incorporates logic, storage, and communication for computing—based on a combination of electronic, spintronic, photonic, and optical technologies. Precise production and integrated use of many different materials will be a hallmark of future advanced device technology. 

D.S. Chemla, D.A.B. Miller, and P.W. Smith, Nonlinear Optical Properties of Multiple Quantum Well Structures for Optical Signal Processing... 

While the linear absorption and nonlinear optical properties of certain dendrimer nanocomposites have evolved substantially and show strong potential for future applications, the physical processes governing the emission properties in these systems is a subject of recent high interest. It is still not completely understood how emission in metal nanocomposites originates and how this relates to their (CW) optical spectra. As stated above, the emission properties in bulk metals are very weak. However, there are some processes associated with a small particle size (such as local field enhancement [108], surface effects [29], quantum confinement [109]) which could lead in general to the enhancement of the fluorescence efficiency as compared to bulk metal and make the fluorescence signal well detectable [110, 111]. 

Pickering and co-workers observed visible photoluminescence (PL) from PS at 4.2 K in 1984 [Pil], which they interpreted as due to a complex mixture of amorphous phases. The questions of why PS is transparent for visible light and why it is photoluminescent remained unanswered until 1990-91 when a quantum size effect was proposed as an explanation [Cal, Lei]. Two years later PL was also found for oxidized PS [Lel5, It2]. These astonishing optical properties of PS initiated vigorous research and resulted in more than a thousand publications, as well as several books and reviews [Cu2, Th7]. 

The smallest pores that can be formed electrochemically in silicon have radii of < 1 nm and are therefore truly microporous. However, confinement effects proposed to be responsible for micropore formation extend well into the lower mesoporous regime and in addition are largely determined by skeleton size, not by pore size. Therefore the IUPAC convention of pore size will not be applied strictly and all PS properties that are dominated by quantum size effects, for example the optical properties, will be discussed in Chapter 7, independently of actual pore size. Furthermore, it is useful in some cases to compare the properties of different pore size regimes. Meso PS, for example, has roughly the same internal surface area as micro PS but shows only negligible confinement effects. It is therefore perfectly standard to decide whether observations at micro PS samples are surface-related or QC-related. As a result, a few properties of microporous silicon will be discussed in the section about mesoporous materials, and vice versa. Properties of PS common to all size regimes, e.g. growth rate, porosity or dissolution valence, will be discussed in this chapter. 

R. Cingolani, Optical Properties of Excitons in ZnSe-Based Quantum Well Heterostructures A. Ishihashi and A. V. Nurmikko, II-VI Diode Lasers A Current View of Device Performance... 

H. Morkoc, F. Hamdani, and A. Salvador, Electronic and Optical Properties of IIT-V Nitride based Quantum Wells and Superlattices K. Doverspike and J. /. Pankove, Doping in the 111-Nitrides... 

Interfaces are of critical importance in determining the electronic and optical properties of quantum well heterostructures. It is necessary to... 

Indeed we study the two-dimensional systems in Section 5. In this section we will analyze the structural, electronic and, in particular, the optical properties of Si and Ge based nanofilms (Section 5.1), of Si superlattices and multiple quantum wells where CalQ and SiC>2 are the barrier mediums (Sections 5.2 and 5.3). The quantum confinement effect and the role of symmetry will be considered, changing the slab thickness and orientation, and also the role of interface O vacancies will be discussed. 

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