Thermodynamics of the pseudobinary GaAs1-xBix (0 ≤ x ≤ 1) alloys studied by different exchange-correlation functionals, special quasi-random structures and Monte Carlo simulations

Spontaneous formation of three-dimensionally ordered Bi-rich nanostructures within GaAs1−xBix/GaAs quantum wells

“…Hence the resulting microstructure consists on a three-dimensionally (3D) ordered assembly of Bi-rich entities. In accordance with theory, we argue that in this particular system the formation of the Bi-rich units is driven by thermodynamics where the large miscibility gap between GaAs and Bi triggers the phase separation [2,4]. Likewise we find that the thermodynamically-driven spontaneously formed Bi-rich nanostructures are remarkably uniform in size and Bi-distribution, suggesting their potential application as new functional units for future optoelectronic and/or spintronic devices based on bismides.…”

“…separation is driven by the large miscibility gap [2,4]. Nevertheless, the high degree in vertical alignment of the Birich structures can be understood in terms of the strain fields associated to the Bi-rich areas, in addition to the strong impact of the considerable Bi surface segregation which necessarily affects the microstructure of the subsequent layers, i.e.…”

“…There are, nevertheless, many material-related challenges stemming from the fact that III-V-Bi compounds are highly-mismatched alloys, which are formed by the substitution of isoelectronic elements with very different size and/or electronegativity. Recently, Gibbs formation energies and the immiscibility curve of Ga(As,Bi) were theoretically determined using different methods, evidencing that the thermodynamics of GaAs 1−x Bi x alloys strongly favor decomposition [2]. Experiments demonstrate, however, that it is possible to control the layers microstructure with appropriate growth conditions, where kinetics plays a significant role in inhibiting phase decomposition and enhancing Bi incorporation [3,4].…”

Self-selective formation of ordered 1D and 2D GaBi structures on wurtzite GaAs nanowire surfaces

“…Bi atoms situated below the surface layer would give rise to a much smaller outward relaxation (towards the vacuum), which should still be detectable with STM down to at least 3 bilayers 34 , however, we find no such protrusions. These results suggest Bi-incorporation on GaAs NWs after growth as a successful approach for achieving local GaBi formation, which has been considered unstable in bulk [25][26][27] , confined within the top most atomic layer.…”

“…GaBi compounds, for example, have been predicted to show band inversion and topological behavior 21,22 . However, III-V alloys with a high Bi content (>20% of the group-V atoms) could not yet be realized 23,24 , and especially GaBi has been considered as thermodynamically unstable [25][26][27] , while Bi is also known to act as surfactant in the GaAs/InAs material system 28 . Alternatively, one can consider to deposit Bi atoms onto the surfaces of binary III-V compounds and thus obtain a high Bi concentration at the surface.…”