Pattern formation in PbTe multilayer films

Atomic force microscopy is used to study the surface morphology evolution of PbTe films that have been grown by hot-wall epitaxy on BaF2(111) substrates. We found that the morphology strongly depends on the doping type of the films. For film thicknesses of about 1500 nm, Te rich films (p-type) show uniform pyramids with hexagonal bases whereas Pb rich films (n-type) exhibit irregularly shaped crystallites with (111) terraces on top. By growing npn multilayers we observe the formation of uniform triangular pyramids in the second n-layer. The arrangement of the pyramids can be controlled by varying the thickness of the p-layer. In addition to this pattern formation, the insertion of the p-layers reduces the surface roughness compared with that of the single n-layers.