HARD HETEROEPITAXY ON 2-DEGREES OFF-ORIENTED GAAS (100) SUBSTRATES .1. THE OCCURRENCE OF (100) AND (111) SURFACE ORIENTATIONS IN MBE-GROWN PBTE FILMS

The MBE growth of PbTe layers on GaAs (100) 2-degrees off-oriented sub strates belongs to hard heteroepitaxy, because the two materials diffe r strongly in their lattice constants and, in addition, they also exhi bit different crystal structures. Consequently, phases with different surface orientations may occur in MBE-grown PbTe epilayers. Two crysta llographic orientations, i.e. (100) and (111), have been found in the PbTe epilayers grown by MBE on these off-oriented substrates. X-ray di ffraction and reflection high energy electron diffraction (RHEED) meas urements applied as post growth characterization techniques allow to i dentify which orientation is prevailing in films grown at different MB E conditions. It has been shown that the occurrence of the (100) and ( 111) orientations in MBE-grown PbTe epilayers depends mainly on the Ga As substrate in situ preheating procedure. At higher preheating temper ature and longer preheating time the (111) orientation prevails. This finding is in accordance with the theoretical model of hard heteroepit axy of CdTe on GaAs (100) substrates by GRIESCHE et al.