GaN on Si Power and RF Devices and Application.

GaN-based High Electron Mobility Transistors (HEMTs) are well suited to high power/frequency applications thanks to the many intrinsic benefits of the material. During the operation in actual applications, e.g., in power converters, GaN devices are switching for many cycles, thus inducing power dissipation (conduction and switching losses). Therefore, heat production generates an increase of the device temperature, drifting its characteristics from the ones expected at room temperature. Therefore, p-GaN gate transistors have been deeply analyzed both in DC and dynamic conditions at high operating temperature (up to $150^{\circ}$C). The relevance of the resistive component under the p-GaN gate in the 100V technology under exam has been proved, showing that its increase with temperature is caused by the positive VTH shift and by the gm degradation, so is important to achieve a stable Vth in temperature. RF applications usually do not require normally-off operation, enabling the exploitation of the total 2DEG density. Moreover, requirements for RF devices typically involve high maximum saturation current and high output power at high frequency operation. The trade-off between DC/RF performances and reliability specifications has been analysed by comparing devices with increasing Aluminum concentration in the AlGaN barrier: an optimal Al% must be chosen for ensuring adequate device robustness while targeting sufficiently high current and power levels.