Epitaxial phases of high Bi content GaSbBi alloys

GaSbBi is a relative newcomer in the III-V-Bi family that has experienced rapid development in the past few years, culminating in the first demonstration of a GaSbBi based laser diode [1]. Likewise to other III-V-Bi compounds, while there exists a number of articles on the growth and resulting properties, there is a lack of a comprehensive picture on the intricate details between Bi incorporation, structural properties and epitaxial parameters. This is why we have chosen a systematic methodology [2] based on combinatorial molecular beam epitaxy to investigate a large portion of the growth parameter space in high resolution [3].
Our results reveal three distinct phases in GaSbBi epitaxy, classified by shared properties in terms of Bi incorporation, surface structure and crystallinity. Namely, in phase I we find Ga-Bi compound droplets on the surface, as common in other III-V-Bi compounds, together with decreased crystalline quality and reduced Bi content. In the next phase (phase II), we find optimal structural quality in terms of smooth surfaces with excellent crystallinity and high Bi incorporation. In the last phase (phase III), the Bi incorporation rate is decreased resulting in Bi droplets and, again, poor crystalline quality. In Figure 1, we have mapped these phases as a function of Sb/Ga flux ratio and growth temperature to distinct regimes. In our presentation, we will further show how these phases evolve with increase of the Bi/Ga ratio as well as the growth rate, and discuss these behaviors in the context of different kinetic processes.

[1] Delorme et al., Appl. Phys. Lett. 110 (2017) 222106; http://dx.doi.org/10.1063/1.4984799
[2] Puustinen et al., J. Cryst. Growth 511 (2019) 33-41; https://doi.org/10.1016/j.jcrysgro.2019.01.010
[3] Hilska et al., J. Cryst. Growth 516 (2019) 67-71; https://doi.org/10.1016/j.jcrysgro.2019.03.028