Showing papers by "Theodore I. Kamins published in 2014"

Demonstration of a Ge/GeSn/Ge quantum-well microdisk resonator on silicon: enabling high-quality Ge(Sn) materials for micro- and nanophotonics.

Abstract: We theoretically study and experimentally demonstrate a pseudomorphic Ge/Ge0.92Sn0.08/Ge quantum-well microdisk resonator on Ge/Si (001) as a route toward a compact GeSn-based laser on silicon. The structure theoretically exhibits many electronic and optical advantages in laser design, and microdisk resonators using these structures can be precisely fabricated away from highly defective regions in the Ge buffer using a novel etch-stop process. Photoluminescence measurements on 2.7 μm diameter microdisks reveal sharp whispering-gallery-mode resonances (Q > 340) with strong luminescence.

A new electro-absorption modulator structure based on Ge/SiGe coupled quantum wells for on-chip optical interconnects

Abstract: In this paper, a novel electro-absorption modulation mechanism based on coupled-quantum-wells (CQWs) is proposed and demonstrated. Compared to a quantum-confined-stark-effect (QCSE) modulator with multiple fully decoupled single-QWs, the newly designed CQW modulator has two sub-quantum-wells partially coupled with a small barrier in between. Modulation is based on the change of electron and hole wave-function overlap in the CQWs, which requires a small bias electric field of 50 kV/cm bias electrical field. Theoretically, the power consumption of this new CQW modulator can be lower than 20 fJ/bit and the speed can be higher than 10 Gbps, which outperforms the best Ge/SiGe QCSE modulator that has been previously demonstrated. A proof-of-concept Ge/SiGe CQW modulator based on this novel modulation mechanism was designed and fabricated. Instead of a traditional PIN diode structure, the new CQW modulator uses a PIP structure.

Enhanced photoluminescence from Ge/SiGe quantum wells by epitaxial growth induced strain

Abstract: We demonstrate enhanced photoluminescence from Ge/SiGe quantum wells with strain from -0.28% (compressive) to 0.25% (tensile) achieved by epitaxial growth techniques. The intensity enhancement and peak shift from photoluminescence measurements are in agreement with theoretical calculations.