Date of Graduation

12-2020

Document Type

Thesis

Degree Name

Master of Science in Microelectronics-Photonics (MS)

Degree Level

Graduate

Department

Microelectronics-Photonics

Advisor/Mentor

Shui-Qing Yu

Committee Member

Zhong Chen

Second Committee Member

Gregory Salamo

Third Committee Member

Rick Wise

Keywords

Electroluminescence, FTIR, GeSn, Laser, Spectroscopy

Abstract

Photoluminescence (PL) and Electroluminescence (EL) characterization techniques are important tools for studying the optical and electrical properties of (Si)GeSn. Light emission from these PL and EL measurements provides relevant information on material quality, bandgap energy, current density, and device efficiency. Prior to this work, the in-house PL set-up of this lab which involves the use of a commercially-obtained dispersive spectrometer was used for characterizing both GeSn thin film and fabricated devices, but these measurements were limited by issues bordering on low spectral resolution, spectral artifacts, and poor signal-to-noise ratio (SNR) thereby resulting in the possible loss of vital information and inaccurately reported parameters.

To maintain the progress of the GeSn material development toward replacing the group III-V semiconductors in the optoelectronics industry, high-resolution spectroscopy with high SNR are necessary to accurately determine the unknowns in the GeSn growth conditions, device fabrication, and material development. In this work, PL and EL characterization systems were designed, built, and aligned using a Bruker Fourier transform infrared (FTIR) set up to collect the emission from fabricated GeSn samples using an external source with an external photodetector.

This thesis presents an optical setup of a Bruker FTIR spectrometer aligned with external optical components and external light sources (532 nm laser and 1064 nm laser) to achieve high-resolution spectroscopy with high SNR. The setup employs the use of OPUS operational software for controlling the components of the FTIR hardware and a LabVIEW program for controlling all motorized devices on the external optical bench. An indium antimonide (InSb) external photodetector was used with the FTIR for a wider spectral range detection. Finally, a step-scan mode of operation which required both lock-in and a chopper was used to measure various GeSn bulk and laser samples at high resolution. The results obtained from these characterizations demonstrate a high SNR spectrum compared to a dispersive spectrometer.

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