Lateral Heat Spreaders Research Articles

Graphene quilts for thermal management of high-power GaN transistors

Self-heating is a severe problem for high-power gallium nitride (GaN) electronic and optoelectronic devices. Various thermal management solutions, for example, flip-chip bonding or composite substrates, have been attempted. However, temperature rise due to dissipated heat still limits applications of the nitride-based technology. Here we show that thermal management of GaN transistors can be substantially improved via introduction of alternative heat-escaping channels implemented with few-layer graphene-an excellent heat conductor. The graphene-graphite quilts were formed on top of AlGaN/GaN transistors on SiC substrates. Using micro-Raman spectroscopy for in situ monitoring we demonstrated that temperature of the hotspots can be lowered by ∼20 °C in transistors operating at ∼13 W mm(-1), which corresponds to an order-of-magnitude increase in the device lifetime. The simulations indicate that graphene quilts perform even better in GaN devices on sapphire substrates. The proposed local heat spreading with materials that preserve their thermal properties at nanometre scale represents a transformative change in thermal management.

Experimental Demonstration of Thermal Management of High-Power GaN Transistors with Graphene Lateral Heat Spreaders

ABSTRACTGraphene is a promising candidate material for thermal management of high-power electronics owing to its high intrinsic thermal conductivity. Here we report preliminary results of the proof-of-concept demonstration of graphene lateral heat spreaders. Graphene flakes were transferred on top of GaN devices through the mechanical exfoliation method. The temperature rise in the GaN device channels was monitored in-situ using micro-Raman spectroscopy. The local temperature was measured from the shift in the Raman peak positions. By comparing Raman spectra of GaN devices with and without graphene heat spreader, we demonstrated that graphene lateral heat spreaders effectively reduced the local temperature by ~ 20oC for a given dissipated power density. Numerical simulation of heat dissipation in the considered device structures gave results consistent with the experimental data.

Heat Removal in Silicon-on-Insulator Integrated Circuits With Graphene Lateral Heat Spreaders

Graphene was recently proposed as a material for heat removal owing to its extremely high thermal conductivity. We simulated heat propagation in silicon-on-insulator (SOI) circuits with and without graphene lateral heat spreaders. Numerical solutions of the heat-propagation equations were obtained using the finite-element method. The analysis was focused on the prototype SOI circuits with the metal-oxide-semiconductor field-effect transistors. It was found that the incorporation of graphene or few-layer graphene (FLG) layers with proper heat sinks can substantially lower the temperature of the localized hot spots. The maximum temperature in the transistor channels was studied as function of graphene's thermal conductivity and the thickness of FLG. The developed model and obtained results are important for the design of graphene heat spreaders and interconnects.