MISFIT AND THREADING DISLOCATIONS IN GAAS-LAYERS GROWN ON SI SUBSTRATES BY MOCVD

The misfit dislocations at GaAs/Si interface and threading dislocations in the GaAs layers grown on Si by MOCVD have been studied by transmission microscopy. The misfit dislocation is a pure edge dislocation with Burgers vector of 1/2 a LT AN BR 110 RT AN BR parallel to the interface. The threading dislocations are either the end portions of the misfit dislocations or dislocations with Burgers vector of 1/2 a LT AN BR 101 RT AN BR inclined to the surface. Most of the threading dislocations are not revealed as conventional large etch pits by molten KOH etching. Therefore, the molten KOH etching underestimates the dislocation density in the GaAs layer by about three orders of magnitude.