Thermal Engineering for Flexible, High-Power Electronics
Consumers and military personnel are demanding faster data speeds only available through fifth generation (5G) wireless communication technology. Furthermore, as wearable sensors and other devices become more ubiquitous, devices demonstrating enhanced flexibility and conformality are necessary. The challenge is to enable electronic devices to withstand strain and continue to operate within an acceptable tolerance to ensure reliability. A fundamental challenge for flexible electronics is thermal management. Even on rigid substrates with 100 times higher thermal conductivity than polymeric and other flexible substrates, the full potential of semiconducting materials is often thermally limited. The flexible gallium nitride (GaN) high electron mobility transistors (HEMTs) employed in this work are grown on a two-dimensional boron nitride (BN) release layer that allows the conventionally processed devices on sapphire wafers to be transferred using a polymeric stamp and placed onto a variety of rigid and flexible substrates. Characterization of the GaN device behavior on the as-grown sapphire wafers (not transferred) provide a baseline for evaluation of the thermal performance. Transferring the GaN devices to flexible substrates enables application of strain during device operation; however, device performance typically suffers due to the low thermal conductivity of most polymeric substrates, requiring more advanced schemes to remove waste heat from device operation. In situ thermal imaging of devices in operation reveals that the current passing through a non-transferred GaN transistor on a sapphire wafer reaches the target operating temperature at twice the current of the same device transferred to a flexible substrate. Packaging environment simulations and consideration of device-substrate interfacial thermal effects allow for an understanding of how the flexible GaN devices operate after they are transferred to a substrate and show the path forward for substrate design to reduce thermal limitation of high-power flexible electronics.
Primary Advisor's Department
Stander Symposium poster
"Thermal Engineering for Flexible, High-Power Electronics" (2018). Stander Symposium Posters. 1318.