High-Accuracy Thermal Resistance Measurement Method for GaN HEMTs Based on Harmonic Pulsewidth Subthreshold

The study on the junction temperature and thermal resistance of gallium nitride (GaN) high electron mobility transistors (HEMTs) becomes essential in order to ensure high operating reliability. Among different categories of thermal resistance measurement methods, the temperature-sensitive electrical parameter (TSEP) method exhibits unique advantages in terms of online implementation, accuracy, and applicability. After reviewing current TSEP methods for GaN HEMTs, this article proposes a high-accuracy thermal resistance measurement method for GaN HEMTs based on a heating power modulation strategy, which is named the harmonic pulsewidth subthreshold (HPWS) method. Specifically, the sensitive linear correlation between the subthreshold swing (SS) of GaN HEMTs and temperature will be utilized, and the turn-off transients of the heating power signal will be sampled to extract the thermal resistance through frequency-domain scanning of the heating signal modulation. Thus, the proposed HPWS method can filter out negative effects caused by case temperature fluctuations and the measurement impulse signal delay, which can minimize possible errors caused by nonlinearity or low sensitivity. An experimental comparison of the proposed method with two classical methods was conducted. Main experimental comparison results of the relationship between GaN HEMT thermal resistance and drain current were also introduced. The experimental results indicated that the differences between the proposed method and two classical methods at all various drain current conditions were less than 2%. Besides, a systematic analysis was conducted on main factors determining the accuracy of the thermal resistance measurement for GaN HEMTs.