Kinetics of droplet formation and Bi incorporation in GaSbBi alloys

Abstract

Bi incorporation in GaAs and GaSb has exhibited some promising properties allowing for potential new materials operating in the infrared regime. The growth of these materials has proven difficult, often leading to surfaces covered in droplets or nonuniformity in the composition. We propose a new kinetic model to capture the dynamics of incorporation and droplet formation in the growth of these alloys. The model accurately predicts trends found experimentally. Furthermore, the model shows that compositional nonuniformity arises due to a reduction in the incorporation rate of Bi caused by the nucleation of droplets.

Epitaxial phases of high Bi content GaSbBi alloys

“…Our earlier analysis of figure 1(e) containing Bi droplets is consistent the reduced Bi content. In fact, the reduced Bi content in phases I and III is consistent with Tait et al's III-V-Bi growth model [40], in which droplet nucleation results in a loss-rate of Bi from the surfactant and thereby reduces the amount of Bi in the crystal termination layer, which governs Bi incorporation. As a whole, the analysis of figure 1(c-f) demonstrates the critical role of Sb/Ga in GaSbBi growth and points to a definite growth window (phase II) with optimal structural quality.…”

GaAsBi: From Molecular Beam Epitaxy Growth to Devices

“…The highest Bi incorporation efficiencies are found near the onset of Bi droplets, [ 111 ] which is unsurprising as the Bi droplets act to remove Bi from the surface. [ 96,108,111,114–118 ] Due to the mobility of Bi droplets, they can give rise to Bi‐poor nanostructures within the GaAsBi matrix. [ 96 ] Ga droplets, on the other hand, appear to promote Bi incorporation via a vapor–liquid–solid mechanism (see the Section 3.6).…”

Microstructure and interface analysis of emerging Ga(Sb,Bi) epilayers and Ga(Sb,Bi)/GaSb quantum wells for optoelectronic applications

“…The presence of a "two-composition layer" (or sequences of layers with different Bi contents and a morphology similar to the one detected here) has been already observed in dilute bismide epilayers, 9,17,25,26 in most cases in connection with the existence of Bi droplets on the surface. 17,[25][26][27] The role of surface droplets during growth of dilute bismides and its impact on Bi incorporation inhomogeneities are currently under active investigation. 9,17,18,[25][26][27] Hence, a comprehensive and dedicated study of the effect of surface droplets on the observed morphology depicted in Figs.…”

“…17,[25][26][27] The role of surface droplets during growth of dilute bismides and its impact on Bi incorporation inhomogeneities are currently under active investigation. 9,17,18,[25][26][27] Hence, a comprehensive and dedicated study of the effect of surface droplets on the observed morphology depicted in Figs. 2(a), 2(b), and 3(a) is definitively necessary and will be considered in future investigations.…”