Diamond wafer as the heat spreader for the thermal dissipation of GaN-based electronic devices

 With the increasing power density and reduced size of the GaN-based electronic power converters, the heat dissipation in the devices becomes the key issue toward the real applications. Diamond wafer, with the highest thermal conductivity among all the natural materials, is of the interest for integration with GaN to dissipate the generated heat from the channel of the AlGaN/ GaN high electron mobility transistors (HEMTs).

Picture 1 key comparison of characteristics between diamond and other semiconductor materials

The current GaN wafers are typically grown on sapphie, silicon (Si), silicon carbide (SiC), or free-standing GaN substrates, whose thermal conductivities are 35, 150, 400, and 280W/mK, respectively, which are far from the requirements. The ideal heat spreader would be a substrate that is both highly thermally conductive and electrically insulating. Diamond, with the thermal conductivity up to 2400W/mK at room temperature for the single crystals, and approaching 2000W/mK for the polycrystals, is the best candidate as a heat spreader for GaN power transistors.Early simulations and modelling showed that the passive thermal extraction by direct contact with diamond could dramatically reduce junction temperatures by 25-50%

The device on SiC had a number of dimensional variables in its favor and demonstrated twice the thermal resistance of that on GaN-on-diamond. By using GaN-on-diamond as opposed to GaN-on-SiC, the operating junction temperature was reduced by 40-45%, and the thermal improvement has tripled the areal RF power density from a GaN transistor.

Picture 2 The operating temperature of the GaN-on-diamond and GaN-on-SiC HEMTs

CSMH is a high-tech enterprise focusing on the research and development, production and sales of wide band-gap semiconductor materials and is committed to becoming the world's leading wide band-gap semiconductor materials company. CSMH now has products such as diamond heat sink, diamond wafer, diamond window, diamond and GaN heterointegration,AIN on diamond, etc.CSMH provides professional and leading diamond products and solutions for domestic and foreign customers.