Thermally Introduced Bismuth Clustering in Ga(P,Bi) Layers under Group V Stabilised Conditions Investigated by Atomic Resolution In Situ (S)TEM

We report the formation of Bi clusters in Ga(P(1-x),Bi(x)) 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(P(92.6)Bi(7.4)) and Ga(P(96.4)Bi(3.6)) layers reveals that the threshold temperature at which the Bi clustering takes place is 600 °C in the Ga(P(92.6)Bi(7.4)) layer. Further thermal treatments up to 750 °C show a relationship between the Bi fraction in the Ga(P(1-x),Bi(x)) 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.