Graphite Nanocomposite Substrates for Improved Performance of Flexible, High-Power AlGaN/GaN Electronic Devices

High-power, flexible electronic devices require substrates that effectively dissipate heat while maintaining mechanical compliance. Nanocomposite substrates with ∼20 μm graphite nanoplatelets were incorporated into a polydimethylsiloxane (PDMS) matrix to improve heat transfer from electronic devices and provide a platform for integration into diverse and useful form factors. The composite substrate material exhibited a 9× increase in thermal conductivity (from 0.2 to 1.8 W m–1 K–1) compared to PDMS while maintaining comparable levels of mechanical flexibility. Thinned 2-μm AlGaN/GaN high electron mobility transistors were directly transferred without an adhesive to the composite substrate from the sapphire growth substrate to investigate the impact of the underlying substrate properties on device performance. The devices on composite substrates exhibit a high DC operation power of 6 W mm–1 and were able to withstand cyclic bending over a 15 mm bend radius with no indication of performance degradation, highlighting the nanocomposite substrate as a suitable means to more fully realize the benefits of high-power, flexible devices.