Microscopic characterization of defects using scanning tunneling microscopy

Using a scanning tunneling microscope (STM) it is possible to get microscop ic characterization of defects in semiconductors. The atomic resolution all ows the study of local atomic configuration, interface roughness or defects migration. Local spectroscopy allows for the determination the local densi ty of state associated with the defect and its charge state. Illustrations of these possibilities are presented concerning the roughness of GaSb-InAs or InP-GaInAs interfaces and InAs quantum boxes buried in GaAs, the diffusi on of vacancy in silicon, silicon dopants in GaAs, the charge slate of the arsenic vacancy in GaAs and finally the STM and scanning tunneling spectros copy (STS) of the antisite As-Ga in GaAs. Finally, a discussion is proposed about a basic problem: how tunneling current occurs through defects? There is a necessary coupling between the energy level associated with the defec t and the conduction or valence bands. This coupling is analysed in terms o f emission and capture rates usually used for electrical characterization o f the defects. Some new experimental suggestions are also proposed concerni ng the determination of the emission rate of a defect using the STM techniq ue. (C) 2000 Elsevier Science S.A. All rights reserved.