Characterization of GeSn semiconductors for optoelectronic devices

Student: Hryhorii Stanchu

Degree: Ph.D., December 2020

Major Professor: Dr. Gregory J. Salamo

Research Area(s):

Conventional Materials & Processes

Modeling & Simulation

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Background/Relevance

  • Photonic devices operating in the near- and mid-infrared spectral regions.

  • The compatibility of SiGeSn with the CMOS technology offers fabrication cost benefits due to monolithic integration of electronics on a single chip.

Innovation

  • Development of X-ray diffraction methods for crystal structure characterization to improve the material and device performance.

Approach

  • CVD grown GeSn/Ge/Si(100) heterostructures with different thickness of the GeSn layer and different mismatch with the Ge buffer.
  • X-ray diffraction spectra measurement and simulation using the kinematical theory of X-ray diffraction.
  • Comparison with the SIMS and TEM measurements.

Key Results

  • The kinematical theory of X-ray diffraction was applied to calculate the diffuse scattering from misfit dislocations at the interfaces between the layers. The position and shape of the diffraction pattern reveal the type and density of misfit dislocations when compared with simulation.

Conclusions

  • The incorporation of Sn into the GeSn epitaxial layers increases with increasing strain relaxation.

  • The simulation of reciprocal space maps reveal the type and densities of misfit dislocations, which are responsible for strain relaxation, in the GeSn epitaxial layers.

Future Work

  • Studying of the annealing processes in GeSn/Ge heterostructures.