Meaning
Thermal excitation of charge carriers that enables them to overcome the potential barrier of a material’s surface dictates leakage currents in power semiconductors. In high temperature electronic devices, thermionic emission can lead to significant leakage currents across Schottky junctions or gate dielectrics. This emission is governed by the Richardson-Dushman equation, which relates the current density to the square of the temperature.
Physical Mechanism
Conduction occurs when the thermal energy of the electrons exceeds the work function of the metal or the barrier height of the semiconductor. This thermionic emission rises exponentially with temperature, making it a serious concern for devices operating in hot environments. Designers must use materials with higher barrier heights to limit this leakage.
Thermal Dissipation
Efficient cooling solutions are required to prevent thermal runaway caused by this temperature-sensitive conduction. High temperatures lead to increased leakage, which in turn generates more heat and can eventually cause device failure.
Reliability Assessment
Temperature-dependent current measurements are performed on power transistors to characterize these leakage currents. Engineers use these measurements to determine the maximum operating temperature limits of the component. The results are used to compile the datasheet limits and thermal guidelines for the system designers.
This characterization ensures that the device can operate safely under all specified environmental conditions.
