New material identified by US Navy could revolutionize computer chip heat dissipation

 

One of the greatest challenges in semiconductor design is finding ways to move waste heat out of a structure and into whatever dissipation area is designed for it. This issue doesn’t get a lot of play — CPU and system cooling, when discussed, tends to focus on finding more efficient ways to remove heat from a heatsink lid or the top of the die. The question of how efficiently heat can be transferred to that point is just as important as what happens to it afterwards. Researchers working at the US Naval Research Laboratory in partnership with Boston College have found a new, extremely efficient transmission method. The secret? Cubic boron arsenide.

According to the research team, the room temperature thermal conductivity of boron arsenide BAs) is higher than 2000 Wm-1K-1. That’s on a level with diamond or graphite, which have the highest bulk values known, but are both extremely difficult to work with or integrate into a product. Mass synthesis and precise application of both diamond and graphite are both difficult, which limits practical uses of their capabilities. Boron arsenide could prove more tractable.

The reason born arsenide conducts heat so effectively is due to vibrational waves (phonons) within the lattice structure. In a conventional metal, heat is carried by electrons. Since electrons also carry an electrical charge, there’s a correlation between a metal’s thermal conductivity and its electrical conductivity at room temperature. Metals like copper and aluminum, that transmit heat well, also tend to carry electricity fairly well, particularly when compared to iron, which is a poor carrier, or lead, which is basically the grumpy llama of the metallic world.

The work being done here is theoretical and based on modeling the known lattice structure of boron, but the math checks out. The lattice structure and known properties of semiconductors, including semiconductor work being done in the III-V group of which boron is part, points to potential applications in solar cells and radiation-hardened circuits. One of the other advantages of boron, unlike a material like diamond, is that III-V semiconductor manufacturing is already an area of ongoing research. Boron can be bonded to gallium arsenide (BGaAs), though data on its efficacy in this configuration is somewhat limited.

Should the researchers’ prediction prove valid, there are undoubtedly uses for this capability. Gallium arsenide is a tricky substrate to work with, which is one reason why silicon has remained the industry standard, but multiple manufacturers are expected to deploy III-V materials in coming years as CMOS scaling becomes ever more difficult. Moving heat away from the transistor could allow for higher performance and reduce the need for cooling in any application where heat buildup is detrimental to product function (which is to say, most of them). Boron has also earned scrutiny in recent years thanks to the way it partners up with graphene. As shown in the image at the top of the story, boron nitride and graphene can be grown side by side, creating nanowires of graphene that are isolated by the boron. These types of applications suggest a great deal more attention may be focused on boron in the future, particularly if production can be ramped to industrial levels.Source: extremetech.com