A new device-first low-temperature bonded gallium nitride (GaN)-on-diamond
high-electronic mobility transistor (HEMT) technology with state-of-the-art,
radio frequency (RF) power performance is described. In this process, the
devices were first fabricated on a GaN-on-silicon carbide (SiC) epitaxial wafer
and were subsequently separated from the SiC and bonded onto a
high-thermal-conductivity diamond substrate. Thermal measurements showed that
the GaN-on-diamond devices maintained equivalent or lower junction temperatures
than their GaN-on-SiC counterparts while delivering more than three-times higher
RF power within the same active area. Such results demonstrate that the GaN
device transfer process is capable of preserving intrinsic transistor electrical
performance while taking advantage of the excellent thermal properties of
diamond substrates. Preliminary step-stress and room-temperature, steady-state
life testing shows that the low-temperature bonded GaN-on-diamond device has no
inherently reliability limiting factor. GaN-on-diamond is ideally suited to
wideband electronic warfare (EW) power amplifiers as they are the most thermally
challenging due to continuous wave (CW) operation and the reduced power-added
efficiency obtained with ultra-wide bandwidth circuit implementations.