Effect Of The Surface Upon Misfit Dislocation Velocities During The Growth And Annealing Of Sige/Si (001) Heterostructures

We have measured the velocity of misfit dislocation threading segments in real time during ultrahigh vacuum (UHV) chemical vapor deposition heteroepitaxial growth of thin SiGe epilayers on Si (001) using ultrahigh vacuum transmission electron microscopy. We observe no measurable difference in dislocation velocities during growth and during post-growth annealing of samples with an atomically clean surface, in contrast to previous observations in the InGaAs/GaAs (001) system. However, dislocations are seen to move approximately three times slower during growth and post-growth UHV annealing than during annealing of samples which have a native oxide present on the surface. We have used post-growth depositions of arsenic and oxygen to investigate the effect of surface condition on dislocation velocities, and discuss possible causes for the increase in dislocation velocities in the presence of a native oxide. These systematic studies suggest a hitherto unappreciated interaction between moving dislocations and the surface in this system. (C) 1998 American Institute of Physics.