Mechanism of formation of 60° and 90° misfit dislocations in semiconductor heterostructures

Multifunctional heterostructures integrated on Si (100)

“…10,11 Since these misfit dislocations represent either a missing plane or an extra plane, the LME paradigm reduces to a matching of planes associated with dislocations. 4,5,[12][13][14] Under LME, once the total misfit exceeded 7%, it was surmised that thin films would turn polycrystalline, with large-angle grain boundaries that degrade carrier transport properties. [6][7][8][9] Extensive advanced electron microscopy studies have clearly established that, under low-mismatch conditions, film relaxation occurs only after the film thickness surpasses a critical thickness and the energetics favor dislocation insertion at the respective interface.…”

“…Here the films are assumed to grow pseudomorphically up to a critical thickness, where it becomes energetically favourable for the film to contain dislocations. [12][13][14]18 As growth proceeds beyond the critical thickness, film relaxation commences gradually as dislocations are first generated on the surface and then glide down to the interface as half loops. This process provides the genesis for two threading dislocations per misfit dislocation that potentially end up being trapped in the film if the misfit dislocation fails to propagate across the entire width of the substrate.…”

“…This process proceeds by the nucleation of dislocations at the free surface and then propagation of these dislocations to the interface. 12,14 Unfortunately, dislocation propagation in oxides can be difficult, introducing significant kinetic barriers to film relaxation. Under this model, the dislocations largely represent either missing planes under compressive stress, where planar spacing of the film is larger than that of the substrate, or extra planes under tensile stress, and thin-film relaxation proceeds in the form of matching of planes across the interface.…”

Formation energies and equilibrium configurations of dislocation arrays with alternating Burgers vectors in layered heterostructures

“…Compared to Glissile 601 MDs, 901 Lomer (pure edge) MDs are more difficult to nucleate due to the sessile nature of each, especially for a small mismatch strain [12,21,23,24], and formation of 901 MDs is energetically favored due to the fact that a 901 dislocation array (DA) is roughly twice as efficient as a 601 DA (with the same dislocation spacing) for relaxing misfit strain. Therefore, it has been observed that relaxing 601 dislocation compensated-pairs (60DCPs) (i.e., those with canceling screw and interface-perpendicular edge components) can climb and coalesce into 901 dislocations [12,14,21,25,26], which may be one mechanism for the TD reduction through annealing [4][5][6][7]. With a view towards enhancing dislocation coalescence, we study the conditions under which a 60DCP array is energetically favored over its homogeneous counterpart.…”

New frontiers in thin film growth and nanomaterials

“…[5,6] Since the dislocations are generated at the film surface and glide to the interface, the Burgers vectors and planes of the dislocations are dictated by the slip vectors and glide planes of the crystal structure of the film. [7] These dislocations represent missing or extra planes depending upon compressive or tensile stress in the film. It should be noted that, for dislocations generated at the edge of the islands during three-dimensional growth, geometrical constraints determine the Burgers vectors of the dislocations at the film-substrate interface.…”