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Strains and Dislocations


Before you can make semiconductors useful in interesting devices, you have to grow the crystal first. In the Growth section, growth methods such as MBE and CVD are expored. A lot of interesting physics is happening during the actual growth and independent from the growth method used, there are very general theories about the formation of a crystal. To summarise, the following reasoning is outlined: 

  • The electronic properties of any device is determined by the electronic band structure of the crystal it is made of.
  • With bandgap engineering, one can make crystals with band structures not found in materials from nature and hence one can make devices with novel properties. 
  • One can change the band structure of a crystal by changing its composition, internal strain and doping concentration.
  • You want the crystals layers to fit nicely without too many defects and artefacts due to mismatch between two layers
  • For the latter you need to understand strain relaxation pathways and diffusion very well.

These notions are introduced in small sections. For details, please consult one of the extensive texts below.  

1 Introduction: What you need to control for bandgap engineering

2 Surfaces, Growth and Strain Relaxation

3 Dislocations 1: Phenomenology

4 Dislocations 2: Equations of Motion

5 3 Rules of Thumb for relaxed Layers

6 Critical Thickness

7 Diffusion


[1] Parsons, J., Relaxation of Strained Silicon on Virtual Substrates, PhD Thesis, in Physics. 2007, University of Warwick: Coventry.

[2] Douglas, J. P. (2004). "Si/SiGe heterostructures: from material and physics to devices and circuits." Semiconductor Science and Technology(10): R75.

[3] Landau and Lifshitz, "Theory of Elasticity", Pergamon Press 1970

[4] Hirth and Lothe, "Theory of Dislocations", Wiley 1982

[5] Hudson, "Surface Science", Wiley 1998

[6] Kasper and Lyutovich (ed),Properties of Silicon Germanium and SiGe:Carbon, EMIS Data Review No. 24, Institution of Electrical Engineers 2006

[7] Frank and van der Merwe, Proceedings of the Royal Society 198 (1949)

[8] Matthews and Blakeslee, Journal of Crystal Growth 27 (1974)

[9] Shiraki and Sakai, Surface Science Reports 59 (2005)

[10] DJ Paul, Semiconductor Science and Technology 19 (2004)

[11] Mehrer, Diffusion in Solids, Springer (2007)