Abstract
We report the formation of Bi clusters in Ga(P1-x,Bix) layers during an in situ (scanning) transmission electron microscopy ((S)TEM) annealing investigation. The non-destructive temperature regime in dependence on the tertiarybutylphosphine (TBP) pressure in the in situ cell was investigated to ensure that the results are not distorted by any destructive behaviour of the crystal during the thermal treatment. The following annealing series of the Ga(P92.6Bi7.4) and Ga(P96.4Bi3.6) layers reveals that the threshold temperature at which the Bi clustering takes place is 600 °C in the Ga(P92.6Bi7.4) layer. Further thermal treatments up to 750 °C show a relationship between the Bi fraction in the Ga(P1-x,Bix) layer and the initial temperature at which the Bi clustering takes place. Finally, we investigate one Bi cluster at atomic resolution conditions. In these conditions, we found that the Bi cluster crystallized in a rhombohedral phase, aligning with its {101} planes parallel to the Ga(P,Bi) {202} planes.
Highlights
We first demonstrate that the used in situ setup facilitates the investigation of III/V semiconductor materials in a TEM in the growth temperature regime since it provides the necessary group V stabilization
We determine the temperature above which the Bi clustering takes place
Based on the two investigated composition values, we find that this initial temperature depends on the actual Bi fraction within the Ga(P1-x,Bix) layers
Summary
We report the formation of Bi clusters in Ga(P1-x,Bix) layers during an in situ (scanning) transmission electron microscopy ((S)TEM) annealing investigation. Bi containing III/V semiconductor materials have seen growing interest due to their strong reduction of the band gap energy even with a small fraction of Bi1–3. With a Bi fraction higher than 10% the spin-orbit splitting becomes even larger than the band gap[5,6] Due to this modification Auger recombination processes can be suppressed, leading to an increased efficiency in photonic devices. In this paper we use in situ (S)TEM to investigate the threshold temperature at which the local Bi clustering take place. Further we investigate the cluster formation process as a function of the Bi fraction of the Ga(P,Bi) layers under group V stabilized conditions. We give a detailed insight into the Bi cluster characteristics under atomic resolution conditions
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