310  misfit dislocations in ZnSe/GaAs(001) heterostructure

Abstract

Strain relaxation in ZnSe/GaAs(001) heterostructure grown by molecular beam epitaxy is studied by transmission electron microscopy. In as-grown samples, an array of perfect misfit dislocations, lying along 310 directions, with Burgers vector (1/2) 011 inclined to the interface is observed. The corresponding threading segments propagate by glide in {331} planes, leaving misfit segments in the interface.From a mechanical equilibrium analysis, it is concluded that, in the case of low misfit (0.27%), the critical thickness for {331} planes is less than for {111} glide. Dislocations with the (1/2) 011 Burgers vector lying along 310 directions are more efficient at relaxing the misfit strain than dislocations lying along 110 directions.

Sources of misfit dislocations in ZnSe/GaAs (001) heterostructures

“…4); that is {133} glide is favoured as compared to {111} glide. (These calculations are performed by considering that the Peierls potential plays only a minor role [5]: indeed the growth temperature range is in the athermal regime of dislocation glide). Note that because of the fourfold symmetry of the misfit stress, all eight 1/2<011>{133} systems are equally stressed.…”

“…Since the Burgers vector of dislocations A is inclined to the interface, these are not the most efficient strain-releasing misfit dislocations. Dislocations lying along <110> directions within the interface plane and with in-plane 1/2<110> Burgers vector are most efficient (efficient component 0.71 a) and are indeed observed in fully relaxed material [5]. From the efficient Burgers vector component and the mean distance between interfacial dislocations, the misfit strain that is released by the observed network is estimated as 6x10 -4 , to be compared to the crystallographic misfit: 27x10 -4 .…”

“…1(a)), which suggests that dislocations A extend into the interface by dislocation glide. From TEM analysis, it was recently shown that the early stages of stress relaxation in this heterostructure proceeds by activation of secondary 1/2<011>{133} slip systems [5].…”

A new relaxation mechanism in nanoscale films

“…Both the structure and physical properties of flat and island films are strongly influenced by misfit stresses whose relaxation often occurs by the nucleation of misfit dislocations (MDs) in film-substrate composite solids (see, for example, [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]). MDs in flat films form if the film thickness exceeds a critical value, which depends on the misfit between the crystal lattice parameters of the film and the substrate (see, for example, the pioneering works [18][19][20], reviews [21,22] and book [23]).…”

Nanoparticles as dislocation sources in nanocomposites

“…A partial relaxation of misfit stresses often occurs by nucleation and evolution of misfit dislocations (MDs) at interphase boundaries in thin-film and bulk nanocomposites; see, e.g., [8][9][10][11][12][13][14][15][16][17][18][19][20]. Commonly misfit stress relaxation is realized through the nucleation of MD semiloops at the free surface, their subsequent glide to the interphase boundary and further expansion [8,9].…”