Temperature dependence of dislocation photoresponse in relaxed GeSi films

Using a near-field scanning optical microscope to perform local photocurrent measurements, we examine the temperature dependence of contrast associated with individual threading dislocations and crosshatch patterns from 12 to 300 K. The observed weak contrast at room temperature and a negative temperature coefficient indicate that the predominant electrical activity comes from shallow centers. This is consistent with intrinsic defects or at most low levels (∼ppb) of contaminants. In addition, the crosshatch contrast displays a long-range variation below 100 K.