Stability of group IV-VI semiconductor alloys

We present transmission electron microscopy results on Pb1-xEuxTe alloys that show evidence for a compositional instability for x0.5 when the alloys are grown on BaF2 substrates. The Pb1-xEuxTe alloy becomes stable at room temperature if a buffer layer of PbTe is grown on the BaF2 substrate prior to the growth of the Pb1-xEuxTe layer. The stabilization of the Pb1-xEuxTe solid solution is the result of the additional energy term due to the strain between the Pb1-xEuxTe film and the PbTe buffer layer. The estimated critical temperatures for decomposition of the Pb1-xEuxTe alloys with and without the PbTe buffer layer are 0 and 366 K, respectively, in accord with the experimental observations.