Analysis of Bi Distribution in Epitaxial GaAsBi by Aberration-Corrected HAADF-STEM

Abstract

The Bi content in GaAs/GaAs1 − xBix/GaAs heterostructures grown by molecular beam epitaxy at a substrate temperature close to 340 °C is investigated by aberration-corrected high-angle annular dark-field techniques. The analysis at low magnification of high-angle annular dark-field scanning transmission electron microscopy images, corroborated by EDX analysis, revealed planar defect-free layers and a non-homogeneous Bi distribution at the interfaces and within the GaAsBi layer. At high magnification, the qHAADF analysis confirmed the inhomogeneous distribution and Bi segregation at the GaAsBi/GaAs interface at low Bi flux and distorted dumbbell shape in areas with higher Bi content. At higher Bi flux, the size of the Bi gathering increases leading to roughly equiaxial Bi-rich particles faceted along zinc blende {111} and uniformly dispersed around the matrix and interfaces. FFT analysis checks the coexistence of two phases in some clusters: a rhombohedral pure Bi (rh-Bi) one surrounded by a zinc blende GaAs1 − xBix matrix. Clusters may be affecting to the local lattice relaxation and leading to a partially relaxed GaAsBi/GaAs system, in good agreement with XRD analysis.

Effect of thermal annealing on the optical and structural properties of (311)B and (001) GaAsBi/GaAs single quantum wells grown by MBE

“…PLEASE CITE THIS ARTICLE AS DOI: 10.1063/1.5140447 (b) a structural disorder due to annealing that can be attributed to the Bi-segregation followed by a structural relaxation in the QW region. This evidence is compelling if we compare with Bi clusters reported by Beladés et al [31]. Nevertheless, corroborating with HR-XRD, the GaAs buffer layer is not visible in the TEM images indicating, therefore, the existence of the same vertical lattice parameter than that from GaAs substrate.…”

HRTEM Study of Size‐Controlled Bi Quantum Dots in Annealed GaAsBi/AlAs Multiple Quantum Well Structure

“…The fact that Bi QDs orient randomly eliminated the possibility to analyze them using HRXRD reciprocal space mapping technique, leaving HRTEM as the only available technique to investigate the properties of Bi QDs in detail. There is still no clear agreement on Bi QD orientation in the literature, some groups report that Bi is oriented such that Bi (102) is parallel to GaAs (220), while others claim that Bi nanoparticles are not coherent with the matrix . Our study supports that Bi QDs are oriented randomly within their host matrix.…”

“…The authors proposed a mechanism of Bi QDs formation that relies on a spinodal surface decomposition at the early growth stages. Inhomogeneous Bi distribution after the annealing and formation of ≈12 nm size rh‐Bi nanoparticles in GaAs/GaAsBi/GaAs, is also reported . This group, however, found that Bi QDs are crystallographically incoherent with their GaAsBi matrix.…”

Plasmon Resonance in a System of Bi Nanoparticles Embedded into (Al,Ga)As Matrix

“…However, the rather small Sb concentration ( ) in the Al Ga As Sb systems grown at LT results in the formation of NPs with an antimony concentration [ 25 ]. In the case of the LT-grown GaAs Bi with ( ), the NPs are composed of almost pure bismuth [ 26 , 27 , 28 ]. Such NPs have a rhobohedral atomic structure and almost spherical shape, with diameters around 10–20 nm.…”