Temperature Sensing System Based on Flexible Temperature Sensors for Implantable GaN Power Devices

Abstract

Gallium nitride (GaN) power devices exhibit pronounced self-heating and highly localized hot-spot formation at high power densities, making accurate junction-temperature monitoring essential for reliability management, especially in implantable and weak-convection environments. In this study, a flexible temperature sensor based on a PVA/PANI/CNT ternary composite is developed through a fully low-temperature, MEMS-compatible fabrication process that enables direct lamination onto GaN chip surfaces. The composite material forms a multiscale conductive framework in which hydrogen-bonded PVA, protonation-regulated PANI, and CNT percolation pathways jointly produce a strong negative temperature coefficient and high sensitivity in the low-temperature regime. Three-dimensional thermal-field simulations elucidate the evolution of hot-spot behavior in GaN devices and confirm the necessity of conformal, internally integrated sensing structures for precise thermal monitoring. Experimental characterization demonstrates that the flexible sensor maintains intimate interfacial coupling, captures transient and steady-state junction-temperature variations with high fidelity, and significantly outperforms external NTC sensors, which underestimate the actual junction temperature by 10–20 °C and exhibit substantial response delays. Array-level measurements further visualize spatial temperature gradients across SBD and MOSFET regions, validating the sensor’s capability for high-resolution thermal mapping. Beyond device-level integration, the sensor also exhibits stable responses in low-amplitude thermal-disturbance scenarios such as respiratory monitoring, indicating its applicability to broader wearable and implantable systems. These results confirm that flexible, integration-oriented thermal sensing provides an effective pathway for enhancing the thermal management and reliability of implantable GaN power electronics