Energy transfer and luminescence enhancement in Er-doped silicon

• Main Author: Chen, Thomas D. (Thomas Duhwa)
• Other Authors: Lionel C. Kimerling.
• Format: Others
• Language: English
• Published: Massachusetts Institute of Technology 2005
• Subjects: Materials Science and Engineering.
• Online Access: http://hdl.handle.net/1721.1/9536

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1999. === Also issued in pages. === Includes bibliographical references (leaves 143-152). === Er-doped silicon (Si:Er) is a promising light emitting material for silicon microphotonics. A study of Si:Er excitation/de-excitation mechanisms and luminescence enchancement is presented in this thesis. A model based on impurity Auger and nonradiative nmltiphonon transitions (NRl\·IPT) is shown to describe the temperature quenching of the photoluminescence (PL) intensity from 4K to 300K This model asserts that the nonradiative Auger process is mainly responsible for the temperature quenching below lOOK, and NRMPT backtransfer process is mainly responsible for the temperature quenching above lOOK. Junction photocufrei1t · spectmscopy (JPCS) measurements confirmed the existence of a backtransfer mechanism that grows with temperature in accordance to the model. In order to circumvent the onset of nonradiative transitions at higher temperatures, spontaneous emission enhancement in nrnltilayer Si/Si02 microcavities was explored as a means to increase the PL intensity. Because multilayer microcavity structures cannot be constructed using single crystal silicon, Er-doped polysilicon (poly-Si:Er) was developed as a light emitting material for these microcavities. The poly-Si:Er material exhibited a luminescence very similar to that of Er in single crystal silicon. By crystallizing poly-Si:Er from amorphous material and performing a post-anneal hydrogenation, a reasonably high PL intensity, which was limited by the excitation power, was attained. Microacavities with poly-Si:Er were fabricated and measured for the first time. Cavity quality factors of -60-300 were measured, and an Er enhancement of -20x was observed. A -lOx enhancement of a small background emission from the polysilicon was also observed. The observed enhancement factors match well with computed enhancement factors derived from electric field intensity distribution within the microcavity structure. Exploratory work in optical gain from Si:Er waveguides and vertically coupled ring resonntors was conducted. A fiber coupling technique for low temperature waveguide transmission experiments was developed for the gain experiments. The transmission spectrum of a 3-cm long waveguide was measured at temperatures down to 125K. Because the temperature could not be lowered without debonding the fiber, a net gain could not be observed in this particular waveguide. The application of stimulated emission in Si:Er devices is analyzed and discussed. === by Thomas Duhwa Chen. === Ph.D.