Deep-Level Transient Spectroscopy

Deep-level transient spectroscopy (DLTS) is a very powerful tool to detect the defect concentration and thermal emission rate of semiconductor deep levels by measuring capacitance transients as a function of temperature. It normally used the Schottky diode or p-n junction as a probe. In the process, the probe is forward biased to fill the defects with free carriers by a pulse voltage. After the pulse, the defects start emitting trapped carriers due to thermal emission. DLTS observes the capacitance of Schottky diode or p-n junctions, where the defect charge state recovery causes the capacitance transient when the temperature varies slowly. The frequency of the repetition of the pulse voltage multiplied by certain constant, depending upon the equipment, is called the rate window. A DLTS peak is generated when the thermal emission rate of the trap is the same as that of the rate window. Because of the strong temperature dependence of the trap emission rates, it is possible to resolve the emission from different traps using an appropriate emission rate window.

Related Cryostats: