Growth and characterization of iron aluminide films on compound semiconductors

Transmission electron microscopy (TEM), selected area electron channeling patterns (SACP), and reflection high-energy electron diffraction (RHEED) are used to investigate the growth and quality of epitaxial iron aluminide films on GaAs(100) substrates. These films are observed to grow layer-by-layer even when the constituents are codeposited. During growth the lattice relaxation is determined from in situ RHEED measurements of the separation of two diffracted beams. After growth TEM measurements of Moiré fringes are used to determine the local residual strain and the Burger's vector of the iron aluminide film. Selected area electron channeling is used to determine the residual strain in the films without thin specimen artifacts. The results indicate that strain in the FeA1 films relaxes by the formation of misfit dislocations with an α<100> Burger's vector. The relaxation does not occur as quickly as the Matthews equilibrium model predicts. Since the FeAl and GaAs have different slip systems, the dislocations inducing the relaxation must nucleate in the epilayer. The defects present suggest growth by nucleation and subsequent climb of dislocation half-loops.