The behavior of dislocations in GaAs substrates during the growth of Ga_xAl_1-xAs epitaxial layers

Infrared elastobirefringence is used to investigate the dislocation distribution in GaAs substrates on which Ga0.35Al0.65As epitaxial layers have been grown at 950 °C using liquid phase epitaxy. A marked asymmetry is observed in the dislocation distributions as regards the two nonequivalent 〈110〉 directions in the (001) plane. The dislocation distributions consist mainly of 60°dislocations and a small number of pure edge dislocations. Almost all the dislocations are of the α type. The dislocation distributions observed are discussed with reference to the properties of the dislocations involved and the temperature dependences of the lattice parameters of the epitaxial layer and the substrate.