Deep Level Transient Spectroscopy (DLTS) is a unique and powerful tool for the study of electrically active defects (known as traps) in semiconductors. DLTS can be used in one of two modes of operation; with Schottky diodes or with p-n junctions. With Schottky diodes, majority carrier traps are observed by the application of a reverse bias pulse, while minority carrier traps can be observed by the application of a forward bias pulse.
The technique works by observing the capacitance transient associated with the change in depletion region width as the diode returns to equilibrium from an initial non-equilibrium state. The capacitance transient is measured as a function of temperature (usually in the range from liquid nitrogen temperature to room temperature 300K or above). By using a double box-car averaging technique peaks at a particular emission rate are found as a function of temperature. By looking for emissions at different rates and monitoring the temperature of the associated peak, an Arrhenius plot allows for the deduction of a trap's activation energy.