GaN-based heterostructures with CVD diamond heat sinks: A new fabrication approach towards efficient electronic devices

Abstract

A new approach to the fabrication of efficient heat sinks for GaN-based transistors is demonstrated. A key feature of this work is the growth of polycrystalline diamond coating on the functional silicon layer of SOI wafers followed by etching of a thick silicon substrate and a thin thermal oxide. As a result, composite epi–ready substrates consisting of a thin (410 nm) monocrystalline silicon functional layer on top of the 150 µm-thick polycrystalline diamond heat sink were fabricated. GaN heterostructures were grown on top of the silicon layer, which resulted in an effective thermal contact between CVD diamond and GaN structure. The packaged ungated transistors were made to analyze the efficiency of the developed heat sink. Improved heat removal structures showed the decrease in surface temperature by more than 50 °C at base temperature of Tb=85 °C and dissipation power of Pdiss=6.9 W/mm compared to conventional GaN-on-SiC technology and by more than 20 °C at Tb=25 °C, Pdiss=6.9 W/mm compared to up-to-date GaN-on-Diamond equivalent transistors reported by other groups. New substrate fabrication technology positively impacts GaN-based device output characteristics and reliability, which is important in improving communication systems, radars, and secondary power supply systems.