Thermal Analysis of AlGaN/GaN Hetero-Structural Gunn Diodes on Different Substrates Through Numerical Simulation

GaN-based planar Gunn diodes are promising terahertz sources for monolithic microwave and terahertz integrated circuits (MMICs and MTICs, respectively) due to high output power and easiness of fabrication and circuit integration. However, high lateral current in the 2DEG channel may lead to failures such as early breakdown and suppression of oscillations. In this paper, we will, for the first time, systematically investigate the thermal effect on DC IV and output RF characteristics of AlGaN/GaN hetero-structural planar Gunn diodes on different substrates including diamond, SiC, Si and sapphire. Our simulation results show that the best RF output performance comes with the devices on diamond substrate and no oscillating current is observed for devices on sapphire substrate. The suppress of Gunn oscillation in the device on sapphire is mainly due to the excessive heat generated in the channel that leads to increase of the dead zone and attenuation of electronic domains. These results will lay theoretical and experimental foundation for realizing not only milliwatt GaN-based terahertz semiconductor oscillators but also other power devices.