Date of Graduation

8-2024

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Microelectronics-Photonics (PhD)

Degree Level

Graduate

Department

Microelectronics-Photonics

Advisor/Mentor

Yu, Shui-Qing

Committee Member

Salamo, Greg

Second Committee Member

Naseem, Hameed

Third Committee Member

El-Ghazaly, Samir

Keywords

Group-IV; Laser; Optoelectronics; SiGeSn

Abstract

Silicon photonic integrated circuits enable the capability of producing on-chip processing of photonic signals, including both emission and detection. Emission materials, however, have been limited for monolithic integration due to high processing temperatures, indirect bandgap materials, and material integration complications. The (Si)GeSn material system has recently attracted attention due to the bandgap transition from the Si and Ge, naturally indirect bandgap, to direct bandgap with sufficient Sn incorporation. Additionally, the low growth temperature (CMOS compatible; <400 >°C) of (Si)GeSn materials can enable the monolithic integration of the highly desired mid-infrared light emission on the Si Photonic platform. This dissertation first discusses a study showing improved quantum confinement in a (Si)GeSn quantum well through an increase in barrier height by utilizing SiGeSn materials for the barrier layer. Then an exploration of (Si)GeSn multiple quantum wells (4-, 6-, and 10-QW) helps find a minimum active region thickness necessary for adequate overlap between the active region and the optical mode to produce gain. Following this, the inclusion of capping layers (on top of the GeSn active region) in the (Si)GeSn layer structure increases the overlap between the optical mode and the active region of the layer structures. Finally, a dual-wavelength single-cavity (Si)GeSn laser is produced through appropriate quantum confinement in the well regions of the layer structure, sufficient optical mode overlap with the active region, and optical mode overlap with a lower layer which is also capable of laser emissions. The dual-wavelength operation is enabled due to the Fermi-level splitting of the band structure between the layers which are producing the lasing. Through these various material and device studies, the production of a single laser cavity capable of producing multiple emissions can extend the sensing capabilities of a single photonic circuit while also minimizing the necessary footprint. With applications such as gas and biological sensing, data communications, and light detection and ranging (LiDAR) systems, the (Si)GeSn material system has the capability to produce low-cost, high-yield, modules to improve the state of the art for monolithic Silicon Photonic Integrated light sources of the future.

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