Date of Graduation

12-2014

Document Type

Thesis

Degree Name

Master of Science in Microelectronics-Photonics (MS)

Degree Level

Graduate

Department

Graduate School

Advisor

Shui-Qing Yu

Committee Member

Hameed Naseem

Second Committee Member

Gregory Salamo

Third Committee Member

Ken Vickers

Keywords

Germanium Tin, Light-Emitting Diode, Optoelectronic Device

Abstract

Silicon based optoelectronic devices have been investigated for decades. However, due to the indirect band gap nature of Si and Ge, developing of efficient light-emitting source on Si is still a challenging topic. GeSn based optoelectronic devices have the great potential to overcome this deficiency for several reasons. By adding more fraction of Sn into Ge, GeSn band gap could be reduced. The narrowed band gap could be developed for near to mid infrared applications. The alloy can even become the direct band gap material with a large Sn composition (beyond 8%). This feature could enhance the light emission from the direct band gap transition. Due to the simple process of GeSn device fabrication, the cost of infrared optoelectronic devices could be reduced. Furthermore, the compatibility of GeSn based devices on complementary metal on semiconductor (CMOS) process enables further opportunities for Si photonic integrated circuits.

This thesis discusses the fabrication and characterization of GeSn optoelectronic devices to prove the great potential of this material. The discussion mainly covers the double hetrostructure (DHS) LED, following with an extension study on photodetector. The grown material was characterized and proved to be high quality using X-Ray diffraction (XRD) and photoluminescence (PL). The LED fabrication process and results are described in detail. Surface emitting LED characterization was studied using the current-voltage (I-V) measurement, electroluminescence (EL), as well as optical power. EL spectra of 6%, 8%, 9%, and 10% Sn LED was measured. Emission due to the direct band was observed. The wavelength of the EL spectrum peak of 2348 nm was achieved for measuring 10% Sn LED. Optical power with an average of 0.2 mW was measured under 100 mA current injection. Surface emitting LED design was developed into three generations serving for different research purposes. Edge emitting LED was fabricated and characterized with I-V and EL measurements. For light-detection, both photoconductors and p-i-n photodiodes were characterized with I-V and the spectral response. The absorption spectral response was measured with different Sn composition devices, showing the extended detection range towards mid infrared. The characterizations of GeSn based optoelectronic devices in this thesis demonstrated the GeSn material is versatile and capable for optoelectronic devices.

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