Characterization of Novel Optoelectronic Semiconductor Materials and Devices

Li, Lijun, Electrical Engineering - School of Engineering and Applied Science, University of Virginia
Campbell, Joe, Department of Electrical and Computer Engineering, University of Virginia

The continuous arrival of novel optoelectronic semiconductor materials and devices in recent years has resulted in a demand for adequate metrology to extract important physical parameters and metrics as well as understanding the fundamentals of material and device physics. This dissertation is dedicated to the development and/or application of four characterization methods. The transient photocurrent method is used to measure mobilities and lifetimes of materials that are used to fabricate organic solar cells, which are very crucial physical parameters related to the device performance. The photoinduced current transient spectroscopy technique is applied for the first time to hybrid solar cells in order to extract the trap density of states, which is not easily accessible otherwise. Low-frequency noise spectroscopy near DC is developed and applied to organic solar cells and high-power photodiodes; the results are correlated with charge conduction processes. Finally, a UHF-band RF system based on resonance-coupled photoconductivity decay for the purpose of contactless measurement of carrier recombination lifetimes in semiconductor wafers is built, and is further improved with in-phase and quadrature (IQ) mixing. All four methods have shown great potential and importance in addressing the new metrological challenges from novel optoelectronic materials and devices. I conclude with proposals for future work related to noise measurement and contactless characterization.

PHD (Doctor of Philosophy)
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