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Antimonide semiconductors (Sb)

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Asymmetry in the nucleation along the [110] and [1-10] directions

GaSb of nucleation on GaAs

During nucleation of GaSb on GaAs, the islands are elongated in the [110] direction (Yi Wang- Thesis University of Caen -2012)

Nature of misfit dislocations

Lomer and pair 60° dislocations

The classic Burgers circuit around a Lomer dislocation or a pair of 60 ° dislocations gives the same result. In PM2E, we have developed image processing procedures able to differentiate between a Lomer dislocation and pairs of 60° dislocations which are very closed to each other (distance 1 nm).

Components of the Burgers vector as determined by our strain analysis procedures

A Lomer dislocation is charaterized by its αy (α for alpha) component which is equal to zero, while a measurable component exists in the case of a pair of 60° dislocations.

Formation mechanisms of misfit dislocations

Formation of dislocations at the interface

The formation of interface dislocations follows the conventional 60°dislocation glide model from the surface toward the interface. Its effectiveness depends on the growth mode used during the epitaxy. In three dimensionnal mode, pure 60° or 60° pairs dislocations are finally observed. Indeed, we have shown that it is the interaction between dislocation already in the interface and one enters the surface that defines the resulting Burger vector ( Lomer , 60 °, 60 ° or pair ). (EPL . 97 68011 (2012))

Threading dislocations in GaSb / GaAs layers grown by molecular beam epitaxy (MBE)

The dislocations propagation though the epitaxial layers result from reaction of defects in the interface that rise. Initially, there are three types of misfit dislocations (Lomer, 60° and 60° pairs). Eventually, for the glide in 111 planes, only 60° dislocations have been observed at the surface of thick GaSb layers. (APL 102, 052102 (2013))

Origin of threading dislocations in GaSb/GaAs

Analysis of "moiré fringes" on a TEM plan view sample shows three types of misfit defects that initiate threading dislocations in GaSb / GaAs. a) (60°) ; b) Lomer ; c) Pairs of 60 °