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Research in Electronic and Optoelectronic Materials and Devices
Jon M. Pikal, Associate Professor of Electrical and Computer Engineering
Ph. 307-766-3172 E-mail: email@example.comAreas of Expertise:
Semiconductor Materials and Devices, Optoelectronic Devices, Solar Cells, Semiconductor Lasers
Our current project in solar cells is a interdisciplinary project between physics, chemistry, geology, and electrical engineering. This project involves using quantum dots attached to ternary oxide nanowires for efficient enery conversion. We will study different materials and attachment methods to investigate how these effect the overall performance of the solar cell.
Our semiconductor laser research centers around investigation of charge carrier processes, specifically carrier capture, escape and recombination in quantum dot semiconductor lasers. The studies look to understand the temperature dependence of the threshold current in long wavelength and optimization of laser materials and structure design.
Current and former graduate students:
- Josh Tomayer
- Baichhabi Yakami
- Shreyas Nitre Seshadri
- Umesh Singh
- Heather Lucero
- Amit Dikshit
- Vishnu Vangapally
- Jason Vap
- Vivian Nelson
- Scott Jacobs
- Richard Vickery
Note: Teaching and research assistanships for graduate students in the Electronic and Optoelectronic
Materials and Devices area are available. For more information contact Dr. Pikal by e-mail (firstname.lastname@example.org) .
"Quantum Dot Sensitized Solar Cells Based on Ternary Metal Oxide Nanowires", Funded by the Department of Energy (2010-2013)
This is an interdisciplinary project with faculty from physics, chemistry, geology, and electrical engineering. In this project we will investigate quantum dot sensitized photovoltaic structures based on ternary metal oxide nanowires. The research is aimed at overcoming difficulties faced by nanoparticle-DSSCs and gaining a deeper understanding of the basic science behind the operation of ternary oxide nanowire-based solar structures. We will study the influence of the composition and morphology of the nanowires and the attachment mechanisms of the quantum dots on charge transport and recombination dynamics in the fabricated PV structures. We will also investigate the long term stability issues of the QDSSCs that are related to material corrosion and dissolution. The research activities have the potential to provide significant improvement in the performance of nanostructured PV.
"Carrier Lifetime and Recombination in 1.3um Quantum Dot Lasers", Funded by the Army Research Office (2001-2004)
Semiconductor lasers are important devices found in many of today’s commercial and military communication systems. These systems typically use optical fiber for the transmitting media allowing for high bandwidth transmission free from electromagnetic interference. The primary wavelengths of interest for these systems are 1.3 um and 1.5 um, as these correspond to the zero dispersion and minimum loss of silica fiber, respectively. Several important problems exist in current long wavelength lasers. The strong temperature dependence of the threshold current necessitates active cooling of the laser, increasing the size, cost, and power requirements of the system. In addition, these lasers are currently made on InP substrates making it very difficult to produce the vertical cavity surface emitting lasers (VCSELs) needed for optimum coupling into optical fiber.
The use of InGaAs/GaAs quantum dot active regions can have an impact on both of these problems. Because the quantum dots are grown on a GaAs substrate, current technology for AlAs/GaAs distributed Bragg reflector mirrors and selective oxidation can be used. In addition, the modified density of states of the quantum dot may dramatically reduce Auger recombination, which is one of the major causes of the temperature dependence of the threshold current in current 1.3 um lasers. While room temperature lasing at 1.3 um has been achieved, a great deal of work is needed to understand the operation of these devices in hopes of optimizing their performance.
The goal of this project is to quantify the importance of the different recombination processes both radiative and non-radiative that contribute to the threshold current in long wavelength Quantum Dot (QD) lasers. The significance of this work is that from measurements of these basic laser properties, and their temperature dependence, we will gain information on the operation of these important quantum dot devices leading to improvements in the design and performance of long wavelength semiconductor lasers. In addition, the measurement and analysis techniques developed in this work will be applicable to quantum dot lasers emitting at other wavelengths.
"Effect of Bias Dependence of the Internal Injection Efficiency on the Determination of Recombination Coefficients in Semiconductor Lasers", Funded by the Univ. of Wyoming Faculty Grant in Aid Program (2000-2001)
A study of the effect of the bias current dependence of the internal injection efficiency on the determination of the carrier recombination coefficients in semiconductor lasers. The recombination coefficients are found from a fit of the measured carrier lifetime as a function of bias current using a model that assumes a constant internal injection efficiency. From theory we know that the injection efficiency is not a constant. The constant efficiency assumption thus adds error to the determination of the recombination coefficients. The goal of this project is to determine the bias dependence of the injection efficiency and include this in our calculation of the recombination coefficients. We will determine the internal injection efficiency from the measured spontaneous emission spectra and the above-threshold slope efficiency of the semiconductor laser. A comparison can then be made between the recombination parameters obtained using both the constant and bias dependent efficiency to determine the importance of this effect.