Long-range order-disorder transition in (GaAs)(1-x)(Ge-2)(x) grown on GaAs(001) and GaAs(111)

We have grown (GaAs)(1-x)(Ge-2)(x) layers on GaAs substrates of both (100) and (111) orientations. High-resolution X-ray diffraction is used to study the zincblende-diamond transition. Our experiments show that the (GaAs)(1-x )(Ge-2)(x) layers grown on (111) substrates do not present a long-range ord er-disorder transition for any Ge concentration (except for x = 1). This fa ct gives the first reported evidence for the confirmation of Holloway and D avis theoretical prediction that the growth direction should have an influe nce in the long-range order parameter. (C) 2000 Elsevier Science Ltd. All r ights reserved.