Resolving Lateral Heat Transport in GaN‐on‐SiC HEMT Structures via Transient Thermometry

ABSTRACT Understanding lateral heat transport in GaN high‐electron‐mobility transistors (HEMTs) is essential for the thermal management of high‐power and high‐frequency electronics. Here, lateral thermal transport in GaN HEMTs on 4H‐SiC is investigated using electrical thermometry. Nonlocal temperature transients are measured using a pulse I–V technique combined with on‐chip resistance thermometry, enabling high temporal and temperature resolution at lateral separations up to 424 from the heated channel. The employed technique resolves diffusion‐controlled transient lateral heat transport, enabled by Joule‐heating pulses that are approximately one order of magnitude shorter than the characteristic thermal diffusion time. Three‐dimensional (3D) finite‐element simulations are combined with the measurements to interpret the transient thermal response and identify the effective lateral thermal diffusion time of the device structure. The analysis further reveals strong lateral thermal coupling between the GaN epilayer and the 4H‐SiC substrate, demonstrating that substrate heat spreading dominates the transient thermal transport. These findings provide a quantitative framework for understanding heat propagation in GaN HEMTs and establish practical guidelines for the thermal design and optimization of next‐generation RF and power electronic technologies.