Growth of InGaAs/GaAs on Offcut Substrates by MOVPE: Influence on Macrosteps and Dislocations Formation

Abstract

A study of the relationship between the macrosteps caused by the substrate misorientation and dislocation nucleation in MOVPE‐grown InGaAs/GaAs is presented. The macrosteps could favour strain relaxation and the decrease of the critical thickness, also by generation of misfit dislocations in the 1/2〈110〉{011} glide system, as they can provide sites for stress accumulation above the average value far from the macrosteps. This adds up to the enhanced homogeneous dislocation nucleation associated with the offcut angle. The use of offcut substrates thus produces both compositional inhomogeneities and an increase of the overall dislocation density.

Ordering growth of InAs quantum dots on ultra-thin InGaAs strained layer

“…For GaAs/In 0.15 Ga 0.85 As system, the Matthews critical thickness of h c is the smallest for glide on the 1/2/1 1 0S{1 1 1} system [8], so here h c is about 12 nm [9]. For a single layer In 0.15 Ga 0.85 As on GaAs substrate, the critical thickness of h p where the dislocation multiplication process takes place [10] is h p E76 nm.…”

“…These dislocations have special directions, so people want to use them to fabricate ordered QDs [4,5]. For example, Fumito Hiwatashi [4] found InAs QDs mainly aligned along [1][2][3][4][5][6][7][8][9][10] on InGaAs layer and thought that was because QDs prefer nucleating in the strainrelaxed regions of the strained layers. But, the regions with dense QDs they got were relatively wide, so the result they got cannot be called perfect ordering growth.…”