Graphene Heat Spreaders Research Articles

Numerical Study of Graphene Heat Spreaders for a THz Quantum Diode Based on a G-MGIM Junction

In the context of a numerical study about mid-infrared receivers based on a metal–insulator–metal junction, we study how a top multilayer of graphene is capable to remove heat from the thin metal layer in which the laser impinges on. Due to its extremely high thermal conductivity, the graphene film (made of several layers) extracts the heat and injects it inside bulky lateral metal paddings of the receiver. Therefore, the lateral metal contacts not only detect the electromagnetic field transforming it into a current through this quantum diode, but they can also help to drain the heat. A metal–insulator–metal junction, which combines Kretschmann illumination and a distributed light on the junction (or are illuminated through a grating), allows introducing the electromagnetic field into the junction, biasing in this manner the insulator all along its entire length. The main challenge is the relationship between the insulator thickness and the electromagnetic wavelength. In the mid-infrared region, the insulator thickness of a few nanometers is several orders of magnitude under the diffraction limit, and the electromagnetic field cannot penetrate directly into the structure. In this way, the described technique delivers the infrared radiation into the junction by means of surface-plasmon-polariton traveling wave (SPP-TW). Therefore, a right illumination improves the diode responsivity considerably. However, rectification demands an extremely asymmetrical current–voltage curve. A layered metal–graphene–insulator–metal makes this feasible especially when an SPP-TW, between the graphene and the insulator, establishes a Seebeck effect resulting in the desired asymmetric characteristic. When sampling, the rectified direct tunneling current is desirable to avoid thermionic emission (inherently slow), as well as to induce the SPP-TW in a better form from the outside of the junction. A cooling mechanism that preserves a high electric conductivity on the top metal contact is required. In this theoretical work, we performed a simulation study of how a sheet of graphene is able to enhance the thermal behavior of the receiver under study.

Thermal management of GaN HEMT devices using serpentine minichannel heat sinks

An experimental and numerical investigation of water-cooled serpentine rectangular minichannel heat sinks (MCHS) has been performed to assess their suitability for the thermal management of gallium nitride (GaN) high-electron-mobility transistors (HEMTs) devices. A Finite Element-based conjugate heat transfer model is developed, validated experimentally and used to determine the optimal minichannel width and number of minichannels for a case with a uniform heat flux of 100 W/cm2. The optimisation process uses a 30 point Optimal Latin Hypercubes Design of Experiments, generated from a permutation genetic algorithm, and accurate metamodels built using a Moving Least Square approach. A Pareto front is then constructed to enable the compromises available between designs with a low pressure drop and those with low thermal resistance to be explored and an appropriate minichannel width and number of minichannels to be chosen. These parameters are then used within conjugate heat transfer models of a serpentine MCHS with silicon, silicon carbide, diamond and graphene heat spreaders placed above a GaN HEMT heating source of area 4.8 × 0.8 mm2, generating 1823 W/cm2. A nanocrystalline diamond (NCD) layer with thickness of 2 µm is mounted on the top surface of the GaN HEMT to function as a heat spreader to mitigate the hot spots. The effect of volumetric flow rate and heat spreader thickness on the chip temperature has been investigated numerically and each of these has been shown to be influential. For example, at a volumetric flow rate of 0.10 l/min, the maximum chip temperature can be reduced from 124.7 °C to 96.7 °C by employing a 25 µm thick graphene heat spreader attached to the serpentine MCHS together with a NCD layer compared with a serpentine MCHS without these heat spreaders.

Graphene Heat Spreaders for Thermal Management of InGaP/GaAs Collector-Up HBTs

We present a novel thermal management design for InGaP/GaAs power amplifiers (PAs) by placing the graphene heat spreader (GHS) at the backside of GaAs/InGaAs/InGaP collector-up (C-up) heterojunction bipolar transistors (HBTs), including n-p-n and p-n-p types. The GHS was used to create extra escape channel for thermal spread, and a physics-based analysis was performed to justify heat-dissipation improvements. Temperature distribution in the GHS and the application of these spreaders to ameliorate thermal coupling effects on multifinger transistors were discussed. Compared to the n-p-n device, the p-n-p device exhibits greater thermal stability enhancement results, which are extraordinary and reproducible. Both numerical simulation and experimental measurement were achieved to scrutinize thermal performance of the GHS. This brief demonstrates the potential of the suggested structure in replacing the conventional thermal-removal configuration of GaAs-based HBTs used in high-efficiency cellular handset PAs.

(Invited) Graphene Heat Spreaders and Interconnects for Advanced Electronic Applications

Graphene revealed a number of unique properties beneficial for electronics, including exceptionally high electron mobility and widely tunable Fermi level. However, graphene does not have an electron energy band gap, which presents a serious hurdle for its applications in digital electronics. A possible route for practical use of graphene in electronics is utilization of its exceptionally high thermal conductivity and electron current conducting properties. This invited review outlines the thermal properties of graphene and describes prospective graphene technologies that are not affected by the absence of the energy band gap. The specific examples include heat spreaders, thermal coatings, high-current density electrodes and interconnects. Our results suggest that the thermal management of advanced electronic devices can become the first industry scale application of graphene.

Effect of Diamond and Graphene Heat Spreaders on Characteristics of AlGaN/GaN HEMT

The impact of diamond and graphene heat spreading layers on the thermal and electrical characteristics of AlGaN/GaN high electron mobility transistors (HEMTs) has been investigated using numerical simulations in the hydrodynamic model. It is shown that the introduction of heat spreader significantly reduced maximum device temperature, increased the device lifetime, and improved current-voltage characteristics. The conditions under which the heat spreader works most effectively were found.

Thermal chemical vapor deposition grown graphene heat spreader for thermal management of hot spots

Graphene of different layer numbers was fabricated using thermal chemical vapor deposition (TCVD), and it was demonstrated as a heat spreader in electronic packaging. Platinum thermal evaluation chips were used to evaluate the thermal performance of the graphene heat spreaders. The temperature of a hot spot driven at a heat flux of up to 430Wcm−2 was decreased from 121°C to 108°C (ΔT≈13°C) with the insertion of the monolayer graphene heat spreader, compared with the multilayer (n=6–10) ones’ temperature drop of ∼8°C. Various parameters affecting the thermal performance of graphene heat spreaders were discussed, e.g. layer numbers of graphene, phonon scattering, thermal boundary resistance. We demonstrate the potentials of using a complementary metal oxide semiconductor compatible TCVD process to utilize graphene as a heat spreader for heat dissipation purposes.

Heat Transport in Graphene Interconnect Networks With Graphene Lateral Heat Spreaders

We simulated heat propagation in the integrated graphene heat spreaders within the interconnect hierarchy. In the considered design, the graphene layers perform the dual functions of interconnects and heat spreaders. We investigated Joule heating effects within the chip with graphene interconnect networks and heat spreaders. Numerical solutions for direct current and heat propagation equations were found using the finite-element method. The simulation results showed that the use of graphene as interconnects as well as heat spreaders lowers the maximum temperature of the chip. The maximum temperature of the chip was studied as a function of the interconnect current and thickness of few-layer graphene. Our results are important for design of graphene-based thermal and electrical interconnect networks in the next generations of integrated circuits and 3-D electronics.

Thermal Management in 3-D Integrated Circuits with Graphene Heat Spreaders

Abstract In this paper, we performed thermal analysis in three-dimensional (3-D) chip built on silicon-on insulator substrate. Since heat dissipation is one of the most serious issues in 3-D electronics, efficient thermal management is necessary for reliable and efficient circuit operation. 3-D finite element analysis was used to study the feasibility of the use of graphene in thermal management of 3-D integrated circuits. The simulation results showed that the incorporation of graphene heat spreaders lower the maximum temperature of the chip. We calculated the equivalent thermal resistance for different design schemes and found that larger thermal resistance cause higher temperature rise within the chip. The maximum temperature rise of the chip was studied as a function of dissipated power across the channels and interconnects and thermal conductivity of few-layer graphene. The simulation results are important for the thermal management of three-dimensional integrated circuits and next generation electronics.

Modeling Based Design of Graphene Heat Spreaders and Interconnects in 3-D Integrated Circuits

Computer simulation tools are used to study the feasibility of graphene's applications for thermal management of electronic circuits. We simulated heat propagation in generic 3-D chips built on silicon-on-insulator substrates. Graphene and few-layer graphene were considered to be incorporated within the chips as heat spreaders in order to utilize graphene's extremely high thermal conductivity. They can simultaneously play a role of interconnects. The heat propagation equations were solved numerically using the finite element analysis method. We observed that the incorporation of graphene and few layer graphene with proper heat sinks substantially lowered the temperature of circuits. The maximum temperature within the chip was studied as a function of thermal conductivity of graphene, thickness of few-layer graphene and bonding layer thickness. The simulation results are important for development of the high-heat-flux thermal management approach for semiconductor devices.

Graphene heat spreaders superior to carbon nanotubes and diamond for electronic and photonic devices say Nano Device Laboratory researchers

Graphene heat spreaders superior to carbon nanotubes and diamond for electronic and photonic devices say Nano Device Laboratory researchers

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.