Silicon Nanocrystals for Silicon Photonics

Citation

Walters, Robert Joseph (2007) Silicon Nanocrystals for Silicon Photonics. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/TKXK-8930. https://resolver.caltech.edu/CaltechETD:etd-06042007-160130

Abstract

In the absence of suitable methods for integrating traditional semiconductor optoelectronic materials in CMOS microelectronic fabrication processes, nanostructured silicon has been actively explored as an alternative light emitter for silicon photonics. This thesis presents new experimental results in silicon nanocrystal photophysics and optoelectronics, including novel device designs for optical memory elements and light-emitting structures.

As quantum dots, silicon nanocrystals exhibit several interesting properties including size-tunable emission over visible and near-infrared wavelengths and improved oscillator strength for radiation. In contrast to bulk silicon, nanocrystals can emit light with quantum efficiencies approaching 100%. Through time-resolved photoluminescence measurements, we first quantitatively establish that the dense ensembles of nanocrystals that are attractive in device applications retain these advantages. We then describe the fabrication of fully CMOS compatible silicon nanocrystal optoelectronic test structures and show that such devices can function as room temperature optical memory elements.

We further demonstrate that electroluminescence can be achieved in our devices through a previously unreported process we call field effect electroluminescence, in which sequential charge carrier injection is used to create excitons in silicon nanocrystals. This mechanism is a promising approach for overcoming the difficulty inherent in electrically exciting silicon nanocrystals, which are necessarily surrounded by an electrical insulator. Finally, we present electrically excited infrared light sources that combine carrier injection through the field effect electroluminescence mechanism with near field energy transfer from silicon nanocrystals to infrared emitters.

Thesis Files