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The power of the HEMT-transistors on the substrate from silicon achieves 100 W, on the substrate from silicon carbide - 1.5 kW. This presents high requirements to the quality of heat removal from the crystal active region to case and further to the environment. In the paper the thermal resistance “junction-to-case” the measurement results for GaN HEMT-transistors have been presented. The measurements have been performed using the apparatus, which includes two methods of thermal resistance measurements. In the first method - according to the standard OCT 11 0944-96, a sequence of heating current pulses is passing through the transistor channel and the junction temperature is measured. In the second method the modulated heating power has been used and the response - variable component of the junction temperature has been measured. To exclude the influence of the heating pulses duration, that is typical for the standard method, preliminary measurements of the transient response of the thermal impedance have been performed. To reduce the influence of the delay time, caused by transient electrical processes in the transistor when it switches from the heating mode to the measurement of the thermal sensitive parameter (TSP) mode, an extrapolation of the TSP signal of this parameter has been performed by the end of the heating pulse. The comparative analysis has shown that the measurements results, obtained by the standard and modulation methods differ by less than 2%. The influence of the amplitude of pulses of the heating current heating pulses has been shown. It has been determined that with increasing the heating current the thermal resistance measured values increases, which indicates to the nonlinear nature of the dependence of the temperature in the transistor channel on the power dissipated in it.

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The results of experimental approbation of the method and device for determining the parameters of the thermal circuits of semiconductor products with p-n junctions using the wide-pulse modulation of heating current by the harmonic law on an example of measuring thermal impedance of the power light-emitting diodes have been presented.

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