Power electronics have a wide range of applications, from devices operating at low voltages, for example, in portable electronics, to devices operating at high voltages, for example, in power transmission and distribution systems. Although during the past decades, devices based on silicon (Si) have dominated this field, wide-bandgap semiconductor materials, such as gallium nitride (GaN) and silicon carbide (SiC), have great potential to replace Si in electronic applications. [1] In particular, the 11 times higher breakdown electric field of GaN (GaN: 3.3 MV cm À1 , Si: 0.3 MV cm À1 ) means that for a given film thickness, GaNbased devices can operate at voltages 11 times higher than their Si-based counterparts, and can be significantly smaller, giving potential for lower cost and higher frequency operation. In addition, the larger bandgap energy of GaN makes the devices capable to operate at temperatures greater than 300 °C, which are twice the maximum of those for Si-based components. [2] Silicon carbide is an excellent alternative wide-bandgap semiconductor, however, GaN grown on 200 mm-diameter wafers remains an attractive option. The lower wafer and epitaxy cost, along with the lower technological barriers of processing large-diameter wafers, make Si wafers an excellent alternative to the native GaN substrates, which may show varying quality and limited availability. [3] Moreover, Si, when compared to other low-cost substrates, such as sapphire, shows good electrical and thermal conductivity. Nonetheless, it should be noted that the large lattice mismatch between GaN and Si causes structural defects and a high threading dislocation density in the grown GaN layer. [4] For the growth of GaN on Si, buffer layers are necessary, first, because of the meltback etching effect between Ga and Si, [5] and second, to control the large tensile strain generated in the grown GaN layer, after cooling from the growth temperature, due to the large difference in the thermal expansion coefficients between GaN and Si. The buffer layers, AlN and AlGaN, introduce a compressive strain in the structure to compensate for this tensile strain. [6] For thicker GaN layers, it is difficult to maintain sufficient compressive strain in the layers, thus, limiting the thickness of crack-free GaN layers that can be achieved on planar.