FORMATION OF CYLINDRICAL N-P JUNCTION DIODES BY ARSENIC ENHANCED DIFFUSION ALONG INTERFACIAL MISFIT DISLOCATIONS IN P-TYPE EPITAXIAL SI/SI(GE)

Arsenic enhanced diffusion along individual misfit dislocations in Si/Si(Ge) heterostructures has been detected and imaged using scanning electron microscopy (SEM) and in the electron beam induced current (EBIC) mode. The formation of buried cylindrical, or conical, diodes surrounding misfit dislocations has been observed. The diffusion enhancement is not uniform for each dislocation. EBIC/SEM micrographs reveal a dark recombination contrast in the vicinity of the dislocation core and a white generation signal within the space-charge region of the surrounding n/p diode. Based on an experimental isoconcentration etching profile and a simple model for enhanced diffusion, the dislocation diffusion coefficient for arsenic is estimated to be up to six orders of magnitude higher than that in the host crystal.