Date of Graduation

5-2018

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Engineering (PhD)

Degree Level

Graduate

Department

Electrical Engineering

Advisor/Mentor

Manasreh, Omar O.

Committee Member

Ang, Simon S.

Second Committee Member

Wu, Jingxian

Third Committee Member

Herzog, Joseph B.

Keywords

Enhancement; Nanocrystals; Nanowires; Near-infrared; Optoelectronics; Photovoltaic

Abstract

Investigating semiconductor materials and devices at the nanoscale has become crucial in order to maintain the exponential development in today’s technology. There is a critical need for making devices lower in power consumption and smaller in size. Nanoscale semiconductor materials provide a powerful platform for optoelectronic device engineers. They own interesting properties which include enhanced photoconductivity and size-tunable interband transitions.

In this research, different types of nanostructures were investigated for optoelectronic devices: nanocrystals, nanowires, and thin-films. First, lead selenide nanocrystals with narrow bandgap were synthesized, size-tailored, and functionalized with molecular ligands for the application of uncooled near-infrared photodetectors. The devices showed strong room-temperature responsivity that is covering the entire near-infrared spectral region. In the second investigation self-powered devices based on asymmetric Schottky contacts were designed and fabricated to efficiently detect near-infrared radiations without external biasing. The dimensions and the type of the metal contacts were optimized in order to improve on the device performance. Then silicon nanowires were integrated with the asymmetric contacts to further enhance the performance of the self-powered detectors by increasing the light absorption. Third, an array of gold thin-films was designed to enhance the photocurrent in the near-infrared through the internal photoemission of hot electrons. The photocurrent enhancement was studied as function of thickness and type of the metal thin-film.

Overall, those investigations provided important design considerations for future optoelectronic devices based on nanostructures. Moreover, the implementation of nanostructures with the devices showed superior performance as compared to the bulk.

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