  Mechanical transfer of high performing thin film devices onto arbitrary
substrates represents an exciting opportunity to improve device performance,
explore non-traditional manufacturing approaches, and paves the way for soft,
conformal, and flexible electronics. Using a two-dimensional (2D) boron nitride
(BN) release layer, we demonstrate the transfer of AlGaN/GaN high-electron
mobility transistors (HEMTs) to arbitrary substrates through both direct van
der Waals (vdW) bonding and with a polymer adhesive interlayer. No device
degradation was observed due to the transfer process, and a significant
reduction in device temperature (327 {\deg}C to 132 {\deg}C at 600 mW) was
observed when directly bonded to a silicon carbide (SiC) wafer relative to the
starting wafer. With the use of a benzocyclobutene (BCB) adhesion interlayer,
devices were easily transferred and characterized on Kapton and ceramic films,
representing an exciting opportunity for integration onto arbitrary substrates.
Upon reduction of this polymer adhesive layer thickness, the AlGaN/GaN HEMTs
transferred onto a BCB/SiC substrate resulted in comparable peak temperatures
during operation at powers as high as 600 mW to the as-grown wafer, revealing
that by optimizing interlayer characteristics such as thickness and thermal
conductivity, transferrable devices on polymer layers can still improve
performance outputs.
