Thermal management and packaging

Self-heating

Heat generation is concentrated near the drain-side gate edge. Rising channel temperature reduces mobility and saturation velocity, increases leakage, accelerates trap dynamics, and shortens reliability margins. RF devices can run high continuous power density; power switches can see sharp transient heating during hard switching or fault events.

Substrate choices

• GaN-on-Si: cost-effective and scalable for power devices, but thermal and lattice/CTE mismatch are harder.
• GaN-on-SiC: preferred for high-power RF because SiC offers better thermal conductivity and semi-insulating substrates.
• GaN-on-sapphire: insulating and established, but poor thermal conductivity.
• Bulk GaN / AlN: attractive for advanced devices but expensive and less available.
• GaN-on-diamond: a major research direction for RF and high-power thermal management.

GaN-on-diamond

Diamond has exceptional thermal conductivity, so integrating GaN with diamond can reduce channel temperature and enable higher power density. The hard part is the interface: thermal boundary resistance, bonding damage, nucleation layers, surface roughness, and manufacturability dominate the actual benefit. 2025 work on top-side diamond and GaN-on-diamond emphasizes that the interface can matter as much as the diamond.

Packaging and layout

GaN’s high dv/dt and di/dt make package inductance and PCB layout part of the device. Good designs minimize common-source inductance and power-loop inductance, use Kelvin source connections or integrated drivers, place the driver close to the die, tune slew rate for EMI, and manage third-quadrant conduction/dead time carefully.

Commercial devices increasingly integrate drivers, protection, current sensing, temperature reporting, and top-side cooling because the safest way to use GaN is often to co-design the die, driver, protection, and package.