Microwave Performance of AlGaN/GaN High-Electron-Mobility Transistors on Si/SiO2/Poly-SiC Substrates

The radiofrequency (RF) performance of AlGaN/GaN high-electron-mobility transistors (HEMTs) grown by molecular beam epitaxy (MBE) on Si-on-poly-SiC (SopSiC) substrates formed by the Smart-CutTM process is reported. This provides a low-cost, high-thermal-conductivity substrate for power applications. HEMTs with a 0.5 μm gate length show cutoff frequencies (fT) of 18 to 27 GHz for gate-to-drain distances of 3 to 32 μm and a maximum frequency of oscillation (fmax) of 43 to 47 GHz. The fmax values are slightly lower than comparable devices on sapphire, SiC or Si alone. This approach looks promising for applications requiring cheap large-area substrates and better thermal management than provided by pure Si substrates alone.