Scanning deep level transient spectroscopy (SDLTS)

Scanning Deep Level Transient Spectroscopy (SDLTS) is a current SEM technique for the detection of the local distribution of deep level centres in semiconductors. It is based on the application of the widely used Deep Level Transient Spectroscopy (DLTS), which enables capacitance changes (or current changes) to be measured in a space charge structure after an excitation pulse as a function of the temperature. This makes it possible to detect the energy levels and the concentration of electronic states in the band gap. By means of scanning DLTS–i.e. the excitation of the levels by an electron probe–deep level states can be investigated with a spatial resolution of a few microns. Scanning the pulsed electron beam (at a temperature selected according to an interesting energy level) yields an SDLTS image. Based on the general principle of the measurement and on the necessary instrumentation the practice of the SDLTS signal generation analysis is presented and experimental examples are discussed.