Formation of microtwins in TmP/GaAs heterostructures

Abstract Microtwins in semi-metal thulium phosphide (TmP) epilayers grown on (0 0 1) GaAs substrates by molecular beam epitaxy have been studied by transmission electron microscopy. Selected area diffraction patterns show extra spots along 〈1 1 1〉 and 〈2 2 4〉 corresponding to three times the normal rock-salt periodicity. Only one or two twin variants are found in the crystal. The occurrence of the observed microtwins in the TmP-GaAs heterostructure can be accounted for by the growth-accident mechanism, i.e., the formation of microtwins is via growth accidents in the stacking sequence on {1 1 1} and {1 1 2} planes. The growth accidents appear to occur due to rapid growth rates and/or contamination.