IN-SITU OBSERVATION OF INDIUM SEGREGATION BY REFLECTANCE DIFFERENCE SPECTROSCOPY IN SINGLE MONOLAYER HETEROSTRUCTURES GROWN BY ATOMIC LAYER EPITAXY

Single monolayers of InAs in GaAs and GaAs in InAs have been grown by atomic layer epitaxy (ALE) at 50 Torr. in situ reflectance difference spectroscopy monitoring of the surface during each stage of the growth showed a strong asymmetry in the surface behavior between the two systems. Following insertion of an InAs monolayer in GaAs, approximately 20 ML of GaAs are required to recover an In-free, As-stabilized GaAs surface at 340 degrees C. On the other hand, following the insertion of 1 ML of GaAs in InAs, the spectrum returns to a Ga-free, As-stabilized InAs surface after only 1 ML of InAs deposition. This behavior shows clear evidence of the presence of segregation caused by thermodynamic factors even at the very low growth temperatures used for ALE. (C) 1995 American Institute of Physics.