| About this Abstract |
| Meeting |
2011 Electronic Materials Conference
|
| Symposium
|
2011 Electronic Materials Conference
|
| Presentation Title |
Z4, Fabrication and Characterization of Whispering Gallery Mode (WGM) Microdisk Resonator Based on Epitaxially Grown GeSn |
| Author(s) |
Seongjae Cho, Robert Chen, Hai Lin, Yijie Huo, Gary Shambat, Jelena Vučković, Theodore Kamins, Byung-Gook Park, James Harris |
| On-Site Speaker (Planned) |
Seongjae Cho |
| Abstract Scope |
Whispering gallery mode (WGM) resonators are superior to conventional dielectric resonators in advanced RF circuits, optical communication systems, and biosensing technologies by virtue of their high Q-factor and its invariance at high frequency and both TE and TM mode operation. There have been intensive research efforts on novel materials and processing for silicon-based integrated photonics and optoelectronics. GeSn is considered one of attractive approaches due to its higher carrier mobility, energy bandgap tunability, and integratability on silicon via proper buffer materials. In this work, a WGM microdisk resonator based on epitaxially grown GeSn was successfully fabricated and its optical characteristics were investigated. An In0.16Ga0.84As buffer layer and Ge0.96Sn0.04 were grown on a GaAs substrate by molecular beam epitaxy (MBE) in sequence without exposure to air. Thicknesses were 350 nm and 220 nm, respectively. The 350 nm buffer layer was grown in two segments: first, a 250 nm layer of In0.16Ga0.84As was grown, followed by an anneal at 540 °C for 20 min to minimize the defects caused by lattice mismatch. This was followed by growing an additional 100 nm of In0.16Ga0.84As. The growth temperature for Ge0.96Sn0.04 alloy was 175 ˚C. The device active region was defined by Cr lift-off process and dry etch. Subsequently, the GaAs was chemically etched by H2O:H2O2:H2SO4 = 8:1:1 solution for 20 s at room temperature without stirring. This undercut etch process provides confinement for the optical modes to the disk perimeter and minimizing coupling to the substrate. Light signals were transmitted through a polished optical fiber tapered down to have a diameter of 1 μm in a contact with the fabricated devices. Transmission loss was defined as the difference between intensities of input and output signals at the source and the analyzer, respectively. Three local minima were observed at λ1 = 1430 nm, λ2 = 1560 nm, and λ3 = 1680 nm. Confinement of an optical mode by total internal reflection (TIR) begins at λ1 = 1430 nm but the absorptions at λ1 and λ2 are weak due to material loss. The bandgap edge is predicted to be near 1600 nm judging from a drastic decrease in the curve. The characteristics wavelengths reveal the consecutive integer numbers at which TIRs in the fabricated device occur: 14, 15, and 16 by recursive calculations with effective diameters. |
| Proceedings Inclusion? |
Undecided |