Date of Graduation

12-2011

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Microelectronics-Photonics (PhD)

Degree Level

Graduate

Department

Graduate School

Advisor

Shui-Qing Yu

Committee Member

Hameed Naseem

Second Committee Member

Magda El-Shenawee

Third Committee Member

Greg Salamo

Fourth Committee Member

Rick Wise

Abstract

The electronics industry has a large silicon infrastructure for the manufacture of complementary-metal oxide semiconductor (CMOS) based electronics. The increasing density of Si based circuits has set a pace that is now pushing the physical limits of connectivity between devices over conventional wire based links. This has driven the increasing interest in Si based optoelectronics and to use the groundwork already established by the electronics industry for lower cost optical communications. The greatest limitation to this effort has been the incorporation of a Si based laser, which requires integration of a direct bandgap material within this CMOS process.

The Ge1-xSnx alloy is one material of interest for this field of Si photonics due to its compatibility on Si CMOS circuits and its direct bandgap for increasing Sn content. The past decade of material development in this field has led to Ge1-xSnx films grown on Si with direct bandgaps. The work in this dissertation set out to develop Ge1-xSnx based optoelectronics operating in the short-wave infrared (SWIR) region. The fabrication methodology of Ge1-xSnx active photonic components such as microdisk resonators, photoconductors, and avalanche photodiodes were developed. A simple, one-mask fabrication method was developed to create Ge1-xSnx microdisk resonators on Si, which could serve as a platform for the first on-Si CMOS laser. A study of the noise levels, effective carrier lifetime, and specific detectivity was conducted for the first time on any Ge1-xSnx detector.

A systematic study of detectors with Sn content ranging from 0.9 to 10.0% were fabricated and measured for their responsivity and spectral response in the SWIR. A record high responsivity of 1.63 A/W was measured at the 1.55 μm wavelength for a 10% Sn photoconductor at reduced temperature. A long-wavelength cut-off for this device was measured out to 2.4 μm. Avalanche photodiodes were also developed and tested for devices with Ge1-xSnx absorption regions. The low noise operation and high responsivity of these detectors yield a detectivity that is comparable with commercially available detectors. This work established the baseline performance for this technology and demonstrates this material can be used for Si based optoelectronics.

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