Zugl.: Köln, Dt. Sporthochsch., Staatsexamensarbeit, 2005 / Hergestellt on demand

The thesis focuses on the study of asymmetric multiple quantum wells (AMQWs). There are two main sources of the samples. One is from our laboratory. We used molecular-beam epitaxy to grow the InGaAs/InGaAlAs AMQWs of different well widths and different position arrangement of well width. And we also designed the AMQWs with p-type modulation doping at the different barrier region. The other is from Land Mark Optoelectronics Corporation. They used Metalorganic Chemical Vapor Deposition (MOCVD) to grow the InGaAsP AMQWs of different well widths and different position arrangement of well width. There are five experiments in my thesis. First of all, we use electroluminescence (EL) measurement to discuss the EL spectra of the samples. The EL spectra can show the shape, intensity and full width half maximum. Second, we use the photoreflectance (PR) measurement, which uses laser beam to modulate the dielectric constant of samples, to discuss the transition energies by using simulation and curve fitting. And we got build-in electric field from FKO data and simulation. In the last three experiments, we analyzed photocurrent spectra, photoluminescence spectra and electro-absorption spectra individually and then compared the three to all experiments in the thesis. In these experiments, we discovered that the sample C092 exhibits a broad and flat EL spectrum and 2500Å covering from 1.38~1.63£gm. Besides, we also found that the emission of wells is dominated by the arrangement of quantum wells. Moreover, the arrangement of quantum wells is relative to material. Therefore, even if we use the same way of arrangement, the different materials will lead to different results. Finally, we expect that we can use our AMQWs samples to produce broadly tunable laser and broad-band semiconductor optical amplifier (SOA) in the future.

Abstract The theme of this thesis is the MBE growth of doped arsenide compound semiconductor layers including uniformly doped layers and a modulation-doped heterostructure. The Hall measurement system has been set up to measure the carrier concentration and mobility of these samples. We have also studied the ohmic contacts on epitaxial InGaAs layers by TLM method. For uniformly doped samples, the experimental relation between doping concentration and MBE cell temperature have been established, and are in good agreement with reported results. In the experiment on GaAs/AlGaAs modulation-doped heterostructure, an electron mobility of 27000[cm2/(V•s)] was obtained by cooling the sample down to 170K with liquid nitrogen. This result is consistent with published results. For P-type ohmic contacts on InGaAs, a comparison between two metal layer compositions of Cr+Zn+Au and Cr+Zn+Cr+Au was made. The Cr+Zn+Cr+Au layer gave a lowest specific contact resistance of 3.38¡Ñ10-6(ohm•cm2) at an annealing temperature of 360¢J. A N-type ohmic contact of Au+Ge+Au was also investigated. This metal layer has a lowest specific contact resistance of 9.75¡Ñ10-7(ohm•cm2) without annealing.

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 (M.S.)--West Virginia University, 2002. / Title from document title page. Document formatted into pages; contains iv, 69 p. Includes abstract. Includes bibliographical references.

Zugl.: Berlin, Freie Universiẗat, Diss., 2009.

Light-emitting electrochemical cells (LECs) are solid state polymer devices operating through the formation of a light-emitting p-n junction by in situ electrochemical doping. The LEC film contains a luminescent polymer and a polymer electrolyte. A sufficiently high voltage bias initiates the electrochemical p-doping reaction at the anode interface and n-doping reaction at the cathode interface. With time the doped regions expand in volume until they make contact to form a light-emitting p-n junction. In this thesis, I present my original research on both the light-emitting and photovoltaic properties of LECs. I discovered that continued doping after p- and n-doped regions have made first contact accounts for most of LEC turn-on time. I showed that because the electronic charges must be injected from an external circuit for the electrochemical doping to occur, the LEC turn-on response is limited to no faster than milliseconds. I also demonstrated that the lifetime of LECs can be affected by various factors such as stress temperature, stress current, substrate thermal conductivity, and luminescent polymer end group. With the right combination of substrates and materials, LECs exhibit a remarkable half lifetime on the order of hundreds of hours when stressed at a current density of 1A/cm2. I also observed that an as-formed p-n junction can even relax into a p-i-n junction upon the removal of applied voltage bias. A p-i-n junction LEC exhibits more efficient electroluminescence due to less photoluminescence quenching in the quasi-intrinsic emission zone. Frozen p-i-n junction LECs also exhibit a much improved photovoltaic response. By carefully controlling the relaxation (dedoping) temperature and duration, I have demonstrated p-i-n junction photovoltaic cells with record-high open-circuit voltage of 2.25V and short-circuit current density in excess of 10mA/cm2 under simulated sunlight of ~300mW/cm2. By optimizing film thickness and electrolyte content, I have achieved a thirty-fold increase in power conversion efficiency of p-i-n junction photovoltaic cells. My results demonstrate that a polymer homojunction such a p-n or a p-i-n junction is a promising device concept that has potential application in high performance polymer-based photonic devices. / Thesis (Ph.D, Physics, Engineering Physics and Astronomy) -- Queen's University, 2009-05-25 13:06:45.646

No description available.

Background: There have been doping usage as far back as as ancient Greece and around the early 1900s started the doping we have today. In 2008 it was 22,000 men aged 15-54 years old who had any kind of experience with doping in Sweden. The problem of doping use are all over the world and to overcome this problem, we need to work across borders. Objectives: The purpose of this study is to investigate whether there is any connection between the use of supplements and attitude to doping. The study is based on the questions: is there any connection between the use of supplements and positive attitude to doping? is there any connection between the use of supplements/doping substances and high training frequency? and is there different use of supplement/doping substances between girls and boys? Method: A survey in form of a cross-sectional study and a waiting room survey was conducted with 63 respondents of whom 57,1% were women. Mean age was 24 years. All respondents is studying at Karlstads University. Results: The results of this study shows that unlike previous research, there is no significant difference between the use of supplements and attitude to doping. Neither use of supplements and exercise frequency was incurred any sigificant difference. However there is a significant difference between the use of supplements and girls and boys. The study showed that boys are more likely to use creatine and protein than girls.

Zugl.: Dresden, Techn. Univ., Diplomarbeit u.d.T.: Ökonomische und spieltheoretische Betrachtung der Dopingproblematik im Hochleistungs- bzw. Profisport