Nonradiative Step Facets in Semiconductor Nanowires

Abstract

One of the main advantages of nanowires for functional applications is their high perfection, which results from surface image forces that act on line defects such as dislocations, rendering them unstable and driving them out of the crystal. Here we show that there is a class of step facets that are stable in nanowires, with no long-range strain field or dislocation character. In zinc-blende semiconductors, they take the form of Σ3 (112) facets with heights constrained to be a multiple of three {111} monolayers. Density functional theory calculations show that they act as nonradiative recombination centers and have deleterious effects on nanowire properties. We present experimental observations of these defects on twin boundaries and twins that terminate inside GaAsP nanowires and find that they are indeed always multiples of three monolayers in height. Strategies to use the three-monolayer rule during growth to prevent their formation are discussed.

Optimizing the yield of A-polar GaAs nanowires to achieve defect-free zinc blende structure and enhanced optical functionality

“…It was deemed to be detrimental to the functional properties of the structure, as it can act as a non-radiative recombination center. 42 The NW base also presents twins perpendicular to the growth axis, as in Fig. 3(g).…”

“…31,37,38 The (111) surface energy as well as the nucleation probability of GaAs is also affected by kinetic or thermodynamic factors such as chemical potential in the liquid phase. 2,42 It is very possible that a reduction in the As concentration under lower As fluxes causes the effective energies of A and B surfaces to decrease and increase, respectively. This results in increasing the wetting chance of an A-polar surface with respect to a B-polar surface.…”

Stable Defects in Semiconductor Nanowires

“…We recently observed some types of twin boundary facet that lack strain fields yet act to close the band gap, making them likely nonradiative recombination centres. 12 Any defect with these properties will be deleterious for device performance and reliability. For this reason, it is important to understand the stable defects that may originate from imperfect nanowire growth.…”

Unravelling the strain relaxation processes in silicon nanowire arrays by X-ray diffraction

“…10 10 cm À2 , a mechanism of nanowire coalescence usually manifests itself. This process acts as a strain concentrator (Kavanach, 2010;Grossklaus et al, 2013) and, consequently, strain relaxation can result in the formation of imperfections in the crystal lattice (Sanchez et al, 2017). Depending on the relaxation mechanisms, the strain generated in a nanowire can have a detrimental effect on the electrical/ optical properties through the structural defects generated by its relaxation.…”