We control the formation of Bi-induced nanostructures on the growth of GaAs/GaAsBi core–shell nanowires (NWs). Bi serves as not only a constituent but also a surfactant and nanowire growth catalyst. Thus, we paved a way to achieve unexplored III–V nanostructures employing the characteristic supersaturation of catalyst droplets, structural modifications induced by strain, and incorporation into the host GaAs matrix correlated with crystalline defects and orientations. When Ga is deficient during growth, Bi accumulates on the vertex of core GaAs NWs and serves as a nanowire growth catalyst for the branched structures to azimuthal <112>. We find a strong correlation between Bi accumulation and stacking faults. Furthermore, Bi is preferentially incorporated on the GaAs (112)B surface, leading to spatially selective Bi incorporation into a confined area that has a Bi concentration of over 7%. The obtained GaAs/GaAsBi/GaAs heterostructure with an interface defined by the crystalline twin defects in a zinc-blende structure can be potentially applied to a quantum confined structure. Our finding provides a rational design concept for the creation of GaAsBi based nanostructures and the control of Bi incorporation beyond the fundamental limit.

We report a GaAsBi/GaAs multiple quantum well (MQW) light emitting diode (LED) grown by molecular beam epitaxy using a two-substrate-temperature (TST) technique. In particular, the QWs and the barriers in the intrinsic region were grown at the different temperatures of [Formula: see text] = 350 °C and [Formula: see text] respectively. Investigations of the microstructure using transmission electron microscopy (TEM) reveal homogeneous MQWs free of extended defects. Furthermore, the local determination of the Bi distribution profile across the MQWs region using TEM techniques confirm the uniform Bi distribution, while revealing a slightly chemically graded GaAs-on-GaAsBi interface due to Bi surface segregation. Despite this small broadening, we found that Bi segregation is significantly reduced (up to 18% reduction) compared to previous reports on Bi segregation in GaAsBi/GaAs MQWs. Hence, the TST procedure proves as a very efficient method to reduce Bi segregation and thus increase the quality of the layers and interfaces. These improvements positively reflect in the optical properties. Room temperature photoluminescence and electroluminescence (EL) at 1.23 μm emission wavelength are successfully demonstrated using TST MQWs containing less Bi content than in previous reports. Finally, LED fabricated using the present TST technique show current-voltage (I-V) curves with a forward voltage of 3.3 V at an injection current of 130 mA under 1.0 kA cm current excitation. These results not only demonstrate that TST technique provides optical device quality GaAsBi/GaAs MQWs but highlight the relevance of TST-based growth techniques on the fabrication of future heterostructure devices based on dilute bismides.

We investigated microstructural deformations and Bi segregation in GaAs/GaAsBi/GaAs core–multishell heterostructures, which were triggered by the existence of twin defects. We observed Bi segregation at the interface of the twin defect interface in the GaAsBi shell. The phenomenon produced a horizontally spread Bi-accumulated nanostructure in the nanowire, which is probably induced by the large lattice mismatch between GaAs and GaAsBi. Bi is expected to penetrate through the twin defect interface, which results in the existence of Bi along twin defects and also inside the GaAs core. The existence of twin defects induced structural deformations and resulted in the formation of corrugated complex sidewall surfaces on the nanowire.

We present the growth and strain deformation of sharp-facetted GaAs/GaAsBi core–shell heterostructure nanowires on a Si (111) substrate. The nanowires have a 90 nm wide GaAs core surrounded by an 80 nm thick GaAsBi shell. The sample was analyzed using microbeam synchrotron x-ray diffraction to resolve the local strain status at the GaAs/GaAsBi heterointerface. GaAsBi showed identical lattice constants for its vertical and lateral lattice planes. From the lattice constants, the Bi concentration in GaAsBi was estimated to be approximately 1.3%. In contrast, the GaAs core showed biaxial strain deformation, exhibiting an enlarged vertical lattice constant identical to that of the GaAsBi shell. These layers are coherently grown at the sidewalls of the nanowires, preserving identical vertical lattice constants between the constituent layers in the heterostructure.

No abstract