Microscopic characterization of defects using scanning tunneling microscopy

Using a scanning tunneling microscope (STM), it is possible to get microscopic characterization of defects in semiconductors. The atomic resolution allows the study of local atomic configuration, interface roughness or defects migration. Local spectroscopy allows for the determination the local density 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 diffusion of vacancy in silicon, silicon dopants in GaAs, the charge state of the arsenic vacancy in GaAs and finally the STM and scanning tunneling spectroscopy (STS) of the antisite AsGa 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 defect and the conduction or valence bands. This coupling is analysed in terms of emission and capture rates usually used for electrical characterization of the defects. Some new experimental suggestions are also proposed concerning the determination of the emission rate of a defect using the STM technique.