Negative- U Properties for Interstitial Boron in Silicon

Electrical detection of a single donor level of interstitial boron at Ec-0.13 eV using novel photo---deep-level transient spectroscopy techniques is reported. Complementary behavior between this level and the acceptor level at Ec-0.45 eV establishes that the defect levels have negative-U ordering. The donor level exhibits a large Poole-Frenkel effect which, when properly accounted for, provides a direct and unambiguous connection to the EPR-identified interstitial boron atom. This represents the first definitive indentification of negative-U properties for a defect in any solid.