Analysed the line profiles of the X-ray diffraction patterns of GeSn epilayers and obtained a fitting formula using kinematic scattering to accurately determine dislocation densities in the epilayer.
Supervisor: Professor Sudhasatta Mahapatra, Department of Physics, IIT Bombay
December, 2016 - July, 2017
GeSn epilayers are one way of realizing direct band-gap in silicon and silicon like materials for photonics applications due to the alloying of tin.
In making these epilayers, it is vital to know how much defects they have in terms of dislocation densities. The standard way to determine it is by counting in a Transmission Electron Microscopy scan but this physical counting is not accurate since it extrapolates the dislocations i a few patches to the whole layer.
A more accurate method is to use the X ray diffraction pattern of the whole layer since the broadening of the diffraction peaks are determined by the dislocations.
We used the method developed by Kaganer et al for hexagonal close packed structures for our cubic lattice system to to obtain a fitting formula for our x ray diffraction peaks and obtained accurate estimates of the dislocation density. I built a MATLAB based fitting tool which then fit ou x ray peaks accurately.
The results of this work were used in two publications linked below: