GeSn/SiGeSn Heterostructure and MQW Lasers: towards high efficiency

Student: Solomon Ojo

Degree: M.S., May 2020

Major Professor: Dr. Fisher Yu

Research Area(s):

Microelectronics

Photonics

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Background/Relevance

  • High-performance silicon-based lasers and detectors are sought after, owing to the possibility of monolithic integration of photonics with high-speed Si electronics.

  • GeSn/SiGeSn offer design options from bulk to heterostructure and quantum wells useful for the fabrication of a group IV laser.

Innovation

  • Bandgap engineering for efficient light emission with wide range of wavelength coverage from near to Long-wave infrared.

  • Explore novel growth techniques to reduce defects and gain access to compositions never grown before; high quality and stable (Si)GeSn alloys with high Sn content.

Approach

  • Epitaxial growth of high Sn composition of GeSn and SiGeSn using PEUHV-CVD.
  • LED and laser devices fabrication.
  • Investigate (Si)GeSn electrical and optical properties using Fourier-transform infrared spectroscopy (FTIR).
  • Investigate structural parameters by transmission electron microscopy (TEM) and high resolution X-ray diffraction (HRXRD).
  • Temperature-dependent PL spectroscopy in a cooled closed-cycle cryostat.

Key Results

  • Improved optically pumped GeSn lasers with high operating temperature towards RT.
  • Higher Sn incorporation with optimization of parameters for Plasma Enhancement technique
  • Enhanced radiative recombination due to the localization of electrons and holes in quantum wells.

Conclusions

  • Lasing up to near room temperature, 270 K, which could be attributed to high material quality.
  • Improved carrier confinement by increasing well width, elevating Sn composition in the GeSn buffer layer, and using SiGeSn as barrier.
  • Development of a systematic method to explore the optimal growth condition to achieve higher quality and higher Sn composition.

Future Work

  • MQW development for future devices such as lasers, LED, and photodetector should be further investigated.