Growth of Ge layers with high hole mobility on surface controlled AlAs by molecular beam epitaxy

We examined the surface segregation of Ga, Al and As atoms into the Ge layer for the molecular beam epitaxial growth of Ge on AlAs(1 0 0). We confirmed that the segregation of the Ga atoms which were segregated from the underlying GaAs layer onto AlAs dominates the Ge characteristics. Moreover, we found that Ga segregation is suppressed when Ge is grown on a (5 x 4) AlAs surface, as already discussed in our previous study. We also examined the (5 x 4) AlAs surface and attributed the reconstruction to Ga atoms on the AlAs surface. Moreover, we grew Cc on a Ga-fi ec AlAs surface and obtained a Ge layer with much lower Ga concentration. This resulted in higher hole mobility and lower carrier concentration. (C) 1999 Elsevier Science B.V. All rights reserved.