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

Abstract

High‐resolution transmission electron microscopy (HRTEM) study of statistically large number of Bi quantum dots (QD) in annealed GaAsBi/AlAs multiple quantum well (MQW) structures is presented in this work. Superlattices containing 20 alternating periods of 10 nm thick GaAsBi quantum well and AlAs 20 nm thick barrier layers are grown on semi‐insulating GaAs at 330 °C temperature. Dispersed Bi quantum dots are formed within the bismide layers during a post‐growth annealing at 750 °C. Energy dispersive X‐ray (EDX) mapping and high‐angle annular dark‐field scanning transmission electron microscopy (HAADF‐STEM) analysis reveal that GaAsBi phase is altered during the annealing treatment forming a partially Bi‐depleted GaAsBi phase and semiconducting Bi nanoparticles. AlAs layers are found to act as barriers for Bi out‐diffusion, thus controlling the size of the QDs. The analysis of HRTEM micrographs confirms that Bi quantum dots consist of a rhombohedral Bi phase randomly distributed within zinc blende GaAsBi layers. Geometric phase analysis (GPA) also shows that GaAsBi layers are strained with respect to AlAs layers, as supported by the high‐resolution X‐ray diffraction (HRXRD) data. These findings demonstrate a highly controlled synthesis of Bi‐based quantum dots and pave the way for future applications in the field of infrared devices.

GaAs1-xBix growth on Ge: anti-phase domains, ordering, and exciton localization

“…Bi particles were typically reported to assume a rhombohedral crystal structure within the GaAsBi matrix, and we indeed found numerous coherently aligned Bi crystallites, as illustrated in Fig. 4(b) 48 . Quite a few laterally elongated phase-separated domains were found in the annealed sample.…”

“…6(a) also show XRD of the samples after annealing in RTA oven at 600 °C, indicating a decrease of Bi to 5.2% and 5.5% in S1 and S2, respectively. A decrease of Bi content in GaAsBi lattice is commonly observed in bismides after thermal annealing and can indicate Bi-segregation 46,48 . To investigate CuPt-type ordering, measurements of superlattice reflections were performed in skew-symmetric configurations to access all four distinct sets of {111} planes 49 .…”

GaAsBi: From Molecular Beam Epitaxy Growth to Devices

“…Unlike GaAsBi/GaAs, GaAsBi QWs with AlAs barriers have been shown to prevent Bi out‐diffusion. [ 130,131 ] As a result, the Bi that migrated during the annealing process coalesced to form Bi nanocrystals or dots inside the GaAsBi well. [ 130,131 ] Reports on the effect of annealing on device performance is currently limited.…”

“…[ 130,131 ] As a result, the Bi that migrated during the annealing process coalesced to form Bi nanocrystals or dots inside the GaAsBi well. [ 130,131 ] Reports on the effect of annealing on device performance is currently limited. Recently, Kim et al reported that in situ annealing at 630 °C for 30 min increases PL intensity as well as reduces the J th of a bismide laser from 6 to 5.25 kA cm −2 .…”

Defect‐Induced Effects in Nanomaterials

“…Y. Kuznetsova et al reported the intrinsic defect‐assisted UV‐visible energy conversion in Gd 2 O 3 :Er nanoparticles. M. Skapas et al performed a high‐resolution transmission electron microscopy study of Bi quantum dots in annealed GaAsBi/AlAs multiple quantum wells.…”