The thesis focuses on the broadband characteristic of asymmetric multiple quantum dots . The main sources of the samples are grown from our laboratory. We used molecular beam epitaxy to grow a series samples with different thickness and structures. We also add p type modulation doping in the active layer in asymmetric multiple quantum dots p-i-n laser structures. In our experiment, we use the electroluminescence measurement system to measure the optical signals by adding a forward bias. Then we discuss the spectrum shape, emission intensity, and peak distribution. We also analysis the jump migration between these similar samples. Besides, we use the photo current spectrum, differential absorption coefficient spectrum, and differential refractive coefficient spectrum to analysis the signals. We use sample C240 as our main structure. It organized by three different quantum dots ingredients: In0.64Ga0.36As, In0.75Ga0.25As, and InAs. We find that we get the intensity in C240 is very weak, and the FWMH is 108nm. When we add the quantum dots layer double, we find that the FWHM become 134nm. And then, when we grow 2nm InGaAs quantum well behind the quantum dots structures, the FWMH increases to 156nm. Finally, when we add p type modulation into quantum well, we find the intensity has increased a lot, and the emission wavelength is from 1.18£gm to 1.36£gm. It is about 196nm. By the conclusion, we can find that the emission intensity and FWMH is relative to the different quantum dots layers and doping, we also find that by increasing one quantum layer, we can get the higher FWMH. Finally, we expect that we can use our broadband characteristic of the AMQDs samples to produce broadly tunable laser and broad-band semiconductor optical amplifier in the future.

Thesis (Ph. D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2004. / Srinivasarao, Mohan, Committee Member; Sherrill, C. David, Committee Member; Orlando, Thomas, Committee Member; EL-Sayed, Mostafa, Committee Member; Dickson, Robert, Committee Chair. Vita. Includes bibliographical references (leaves 136-159).

The application of the metalorganic chemical vapour deposition technique to the production of II-VI compound semiconductor electroluminescent devices is discussed. Both low field MIS minority carrier injection devices and high field impact excitation structures are considered, and comparisons are drawn with more commiercially orientated electroluminescent displays. The epitaxial growth of ZnS and ZnSe onto (100) orientated GaAs substrates, using the reactions between dimethyl zinc and the hydrides HgS and H2Se, is described. Details are given of a novel epitaxial MISi device processing technology, in which a ZnS I-layer also acts as an etch-stop, thus enabling chemical removal of the GaAs substrate. Metal electrodes deposited directly onto the ZnS and ZnSe allow the electrical and electroluminescent characteristics of these epitaxial II-VI compound layers to be investigated in the absence of any influence from the substrate material. X-ray diffraction and reflection high energy electron dififraction confirm that the structures are epitaxial and of excellent crystallinity. It is demonstrated in an electron beam induced current study that conduction in the epitaxial MIS devices is highly uniform, and this is manifested in a uniform spatial distribution of electroluminescence. A description is given of high field impact excitation electroluminescent devices, in which the ZnS layer is doped with manganese during MOCVD growth. The spatial distribution of EL in these devices is shown to be non-uniform, and thus indicative of filamentary conduction in the ZnS:Mn, in accordance with a recently proposed dielectric breakdown model of instability. It is demonstrated that the transient characteristics of the epitaxial structures correlate with those of commercial polycrystalline devices, and are also consistent with the predictions of a dynamic model of instability. As a result of filamentary conduction, both epitaxial and polycrystalline devices are prone to degradation through localised dielectric breakdown. These breakdown events generally result in a gradual erosion of the active electrode area, although, under certain operating conditions, mobile filaments can cause rapid destruction of epitaxial structures. The columnar microstructure of sputtered devices appears to prevent such filament mobility, and it is concluded that, although filamentary conduction is a result of the carrier injection mechanism and is independent of the crystallinity, the associated damage is strongly influenced by the microstructure of the device.

The synthesis of a series of poly(arylene vinylene)s via transition metals catalysed polycondensation with a view to producing well defined and clean samples for study , particularly for the incorporation of the material in light emitting devices has been described. Initially the McMurry reaction was applied in the synthesis of poly(4,4'-diphenylene diphenylvinylene). The reaction conditions have been optimised and relatively high molecular weight polymers with narrow molecular weight distributions were produced by fractionating the polymer. The feasibility of the McMurry reaction was established in the synthesis of related polymers; including poly(l,3-phenylene diphenylvinylene), poly(l,3-phenylene dimesitoylvinylene) and poly(4,4'-diphenylene-l,2-bis(pentafluorophenyl)vinylene). In other attempts the Yamamoto and Suzuki polycondensations were applied in the synthesis of structurally defined poly(arylene vinylene)s which could not be made via the route used earlier. Studies on UV-visible absorption, photoluminescence and electroluminescence properties of polymers produced were carried out and correlation between polymer structure and electro-optical properties of the polymer, particularly photoluminescence has been established.

No description available.

Thesis (Ph. D.)--Oregon State University, 2008. / Printout. Includes bibliographical references. Also available on the World Wide Web.

Thesis (M.S.)--Ohio University, Novmeber, 1988. / Title from PDF t.p.

Thesis (Ph. D.)--University of Hong Kong, 1999. / Includes bibliographical references.

Electroluminescence (EL) imaging is a fast and comparatively low-cost method for spatially resolved analysis of photovoltaic (PV) devices. A Silicon CCD or InGaAs camera is used to capture the near infrared radiation, emitted from a forward biased PV device. EL images can be used to identify defects, like cracks and shunts but also to map physical parameters, like series resistance. The lack of suitable image processing routines often prevents automated and setup-independent quantitative analysis. This thesis provides a tool-set, rather than a specific solution to address this problem. Comprehensive and novel procedures to calibrate imaging systems, to evaluate image quality, to normalize images and to extract features are presented. For image quality measurement the signal-to-noise ratio (SNR) is obtained from a set of EL images. Its spatial average depends on the size of the background area within the EL image. In this work the SNR will be calculated spatially resolved and as (background independent) averaged parameter using only one EL image and no additional information of the imaging system. This thesis presents additional methods to measure image sharpness spatially resolved and introduces a new parameter to describe resolvable object size. This allows equalising images of different resolutions and of different sharpness allowing artefact-free comparison. The flat field image scales the emitted EL signal to the detected image intensity. It is often measured through imaging a homogeneous light source such as a red LCD screen in close distance to the camera lens. This measurement however only partially removes vignetting the main contributor to the flat field. This work quantifies the vignetting correction quality and introduces more sophisticated vignetting measurement methods. Especially outdoor EL imaging often includes perspective distortion of the measured PV device. This thesis presents methods to automatically detect and correct for this distortion. This also includes intensity correction due to different irradiance angles. Single-time-effects and hot pixels are image artefacts that can impair the EL image quality. They can conceivably be confused with cell defects. Their detection and removal is described in this thesis. The methods presented enable direct pixel-by-pixel comparison for EL images of the same device taken at different measurement and exposure times, even if imaged by different contractors. EL statistics correlating cell intensity to crack length and PV performance parameters are extracted from EL and dark I-V curves. This allows for spatially resolved performance measurement without the need for laborious flash tests to measure the light I-V- curve. This work aims to convince the EL community of certain calibration- and imaging routines, which will allow setup independent, automatable, standardised and therefore comparable results. Recognizing the benefits of EL imaging for quality control and failure detection, this work paves the way towards cheaper and more reliable PV generation. The code used in this work is made available to public as library and interactive graphical application for scientific image processing.

Luminescence has been observed from water Irradiated with an intense pulse of high energy electrons. The angular dependence, electron energy dependence, visible spectrum, lifetime and yield of the light emission have been determined. In addition, the effect of additives on the emission was studied. The emission spectrum of water was found to be identical to that of methanol, oyclohexane and benzene. All of these results lead to the conclusion that no light emission other than Cerenkov radiation was present in the visible region of the spectrum. The yield of Cerenkov radiation was found to be GhV(4-5000Å)~6x10-4. / Science, Faculty of / Chemistry, Department of / Graduate