Modulating the thermal conductivity in hexagonal boron nitride via controlled boron isotope concentration

Boron Nitride is one of the new exciting wide bandgap semiconductor materials which has emerged recently.

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My group at the University of Bristol has great interest in developing and understanding heat transport in materials and devices. This is as most of today’s electronic and optoelectronic devices are limited by excessive device temperatures which degrade performance and reliability. When a good old friend of mine at Kansas State University, Jim Edgar, contacted me last year that his students managed to grow isotopically pure Boron Nitride we got very excited as this material to date never reached its expected high thermal conductivity; with the isotopically pure Boron Nitride we could demonstrate a thermal conductivity of 585 W/mK, twice that of copper, for the first time – pretty much in line with what theory predicted. We could also test and develop further a transient thermoreflectance technique we previous developed and pioneered for accurate thermal conductivity measurements. This is an easy to use technique to measure lateral and out-of-plane thermal conductivity of materials. Following this work, we now move forward to use the Boron Nitride to make high end electronic devices, but also by integrating it with other semiconductors. Boron Nitride should be able to conduct heat nicely away from many electronic materials when fully integrated. This will allow better performance devices and ultimately higher efficiency electronics which will save energy for a greener society.

Martin Kuball

Professor, University of Bristol

I lead the Center for Device Thermography and Reliability (CDTR) at the University of Bristol. The CDTR is a researcher center with 20 international researchers working on semiconductor electronics (RF and power), in particular thermal management, electrical device design & testing and device reliability. A lot of thrust lies in new materials and new device systems such as GaN, GaN-on-diamond, and Ga2O3 for RF and power applications, ranging from communications, radar, automotive to carbon reducing technology applications. The CDTR collaborates with numerous companies including Element-Six, Infineon, MACOM, Northop Grumman, Qorvo, UMS, WIN Semiconductor and others. We also run large UK Engineering and Physical Sciences Research Council (EPSRC) grants e.g. the Programme Grant GaN-DaME and the Platform Grant MANGI, a £7M investment of EPSRC into Bristol led next generation electronics projects. I co-founded TherMap Solutions ( with two of my postdocs, to spin out key wafer characterization equipment developed as part of my research. I am presently its Chief Business Officer (CBO). I have been awarded a Royal Academy of Engineering Chair in Emerging Technologies, Fellow of IEEE, MRS, SPIE, IET and IoP in recognition of my contributions to the research community.