Date of Graduation

12-2016

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Microelectronics-Photonics (PhD)

Degree Level

Graduate

Department

Graduate School

Advisor

Shui-Qing (fisher) Yu

Committee Member

Gregory Salamo

Second Committee Member

Hameed A. Naseem

Third Committee Member

Simon Ang

Fourth Committee Member

Zhong Chen

Keywords

Applied sciences, Gesn emitters, Infrared, Optoelectronics, Si photonics

Abstract

Conventional integrated electronics have reached a physical limit, and their efficiency has been influenced by the generated heat in the high-density electronic packages. Integrated photonic circuits based on the highly developed Si complementary-metal-oxide-semiconductor (CMOS) infrastructure was proposed as a viable solution; however, Si-based emitters are the most challenging component for the monolithic integrated photonic circuits. The indirect bandgap of silicon and germanium is a bottleneck for the further development of photonic and optoelectronic integrated circuits.

The Ge1-xSnx alloy, a group IV material system compatible with Si CMOS technology, was suggested as a desirable material that theoretically exhibits a direct bandgap when Sn composition increases. Last decade, efforts were made to develop high quality Ge1-xSnx films on Si substrate using commercial reactors. Moreover, the effect of Sn composition on the bandgap energy of Ge1-xSnx alloys was theoretically investigated.

In this work, the development of Si-based Ge1-xSnx emitters was pursued with study the temperature-dependent bandgap emission of Ge1-xSnx structures for the short-wave infrared (SWIR) wavelength range (between 1.5 to 3 µm). The photoluminescence (PL) emissions from the bandgap of Ge1-xSnx films were investigated and a direct bandgap Ge1-xSnx was demonstrated for the first time based on the careful analysis of the PL spectra line-width and also the strain-dependent bandgap concept. In addition, the Ge1-xSnx advanced structure including SiGeSn/GeSn/SiGeSn single quantum well (QW) and Ge/Ge0.92Sn0.08/Ge double heterostructures (DHS) were studied. The GeSn QW PL emission was scrutinized from 10 to 300 K and the carrier confinement was analyzed through band offset calculations in the QW structure. Moreover, the electrical and optical characteristics of n-i-p Ge/Ge0.92Sn0.08/Ge light emitting diodes (LEDs) with surface emitting and edge emitting configurations were examined at different temperatures. Additionally, the lasing performance from the DHS Ge/Ge0.89Sn0.11/Ge waveguide was experimentally investigated based on the concept of direct bandgap Ge1-xSnx films and the confinement of carriers and optical field within the Ge/Ge0.89Sn0.11/Ge structure. Finally, an optimized QW design has been proposed that features a direct bandgap Ge0.9Sn0.1 QW with Type-I band alignment favorable for the high carrier confinement and low threshold Ge1-xSnx QW devices.

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