Date of Graduation

12-2018

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Engineering (PhD)

Degree Level

Graduate

Department

Electrical Engineering

Advisor

Hameed A. Naseem

Committee Member

Shui-Qing Yu

Second Committee Member

Simon Ang

Third Committee Member

Zhong Chen

Fourth Committee Member

Hugh Churchill

Keywords

Group IV Optoelectronics, Growth, Material Science, Microelectronics, Photonics

Abstract

The bright future of silicon (Si) photonics has attracted research interest worldwide. The ultimate goal of this growing field is to develop a group IV based Si foundries that integrate Si-photonics with the current complementary metal–oxide–semiconductor (CMOS) on a single chip for mid-infrared optoelectronics and high speed devices. Even though group IV was used in light detection, such as photoconductors, it is still cannot compete with III-V semiconductors for light generation. This is because most of the group IV elements, such as Si and germanium (Ge), are indirect bandgap materials. Nevertheless, Ge and Si attracted industry attention because they are cheap to be used with low cost and high volume manufacturing. Thus, enhancing their light efficiency is highly desired. A key solution to improve the light efficiency of Ge is by growing tensile strained Ge-on-Si and SixGe1-x-ySny (Sn: tin) alloys. In this dissertation, Si-Ge-Sn material system was grown using chemical vapor deposition technique and further characterized by advanced optical and material techniques. Ge-on-Si was grown at low growth temperatures by using plasma enhancement in order to achieve growth conditions compatible with CMOS technology with high quality Ge layers. First, a single step Ge layer was grown at low temperatures (T 450°C). The material and optical characterization of the single step reveal low material and optical qualities. Second, a two-step Ge-on-Si was grown (T 525°C) to improve the quality. The results show low threading dislocation density on the order of 107 cm-2 with roughness values on the order of several nm. Optical characterization reveal optical quality close to a Ge buffer grown by a traditional high temperature method. In addition, bulk and quantum well SixGe1-x-ySny alloys were grown. The results indicate that lattice matched bulk SiGeSn/Ge can be grown with high optical and material qualities using low cost commercial precursors. In addition, band structure and optical analysis results from a single Ge0.865Sn0.135 quantum well with Si0.04Ge0.895Sn0.065 double barriers on a relaxed Ge0.918Sn0.08 buffer indicate a type-I band alignment with direct bandgap emission. Moreover, SiGeSn barriers improved the optical confinement as compared to GeSn barriers.

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