Diagnostics of the technological characteristics of high–power transistors using relaxation impedance spectrometry of thermal processes

An efficient method of determining thermal parameters in high-power field-effect transistors has been developed and tested based on a study of transient processes during self-heating by direct current. With the developed relaxation spectrometer of the thermal processes, the differential distribution profiles of thermal resistance of KP723G transistors, which were selected in accordance with the regimes of the setting of their crystals, have been investigated. Thermal resistance spectra have been obtained from the analysis of time-dependent dynamic thermal impedance using a new nondestructive method of differential spectroscopy using higher order derivatives (order 3). We present both the continuous (integral) and discrete spectra of the distribution of the internal thermal resistance in the transistors and the value of the junction/case thermal resistance. The thermal characteristics of the KP723G transistors and their imported counterparts IRLZ44 and IRLB3036 have been determined. The method of determining the active region of the devices has been developed and its decrease during heating has been shown. The proposed methodology is useful in solving technological problems for forming the setting layers of the crystals and intermediate layers between the crystal and the heat sink, as well as for the development of thermal models in the SPICE modeling of powerful MOSFETs and diode emitters.