DEFECT STATES IN STRAIN-RELAXED SI0.7GE0.3 LAYERS GROWN AT LOW-TEMPERATURE

Two shallow hole traps dominate the deep level transient spectroscopy (DLTS) data for strain-relaxed Si0.7Ge0.3 layers grown on Si(100) by u ltrahigh vacuum chemical vapor deposition at temperatures less than or equal to 560 degrees C. The trap energy levels are at E-upsilon+0.06 and E-upsilon+0.14 eV and trap concentrations are less than or equal t o 5x10(14) cm(-3) in relaxed layers having threading dislocation densi ties of 2-4x10(7) cm(-2). A logarithmic dependence of the filling rate indicates that these traps are associated with extended defects and t his is confirmed by their absence in a sample having no dislocations. The annealing temperature of the DLTS peaks is consistent with the int erpretation of these traps as states of defect complexes at dislocatio ns. rather than intrinsic dislocation states or isolated defect comple xes. The trap concentrations are proportional to the oxygen concentrat ion in the film, suggesting that oxygen may be a constituent of the de fect complex. (C) 1997 American Institute of Physics.