BEHAVIOR OF MISFIT DISLOCATIONS IN GAAS EPILAYERS GROWN ON SI AT LOW-TEMPERATURE BY MOLECULAR-BEAM EPITAXY

The behavior of misfit dislocations in GaAs buff er layers grown on Si was investigated by the measurement of stresses using optical interferometry and X-ray diffraction. The buffer layers grown at 250-degrees-C with various thicknesses (0.05 approximately 0.20 mum) were annealed at various temperatures (400 approximately 600-degrees-C). The overlayers were grown at 300-degrees-C. With increasing annealing temperature or thickness, the stresses changed from compressive to tensile. The stress-free GaAs/Si wafer was produced with a 0.10-mum-thick buffer layer annealed at 500-degrees-C. These results indicate that in low-temperature growth, it is important to optimize both the annealing temperature and the thickness of the buffer layer. In addition, the asymmetric stresses were observed between [011] and [011BAR]. This asymmetry was caused by the difference in dislocation velocities or nucleation energies between alpha- and beta-dislocations.