The Influence of AlN Nucleation Layer on Radio Frequency Transmission Loss of AlN-on-Si Heterostructure

Reducing radio frequency (RF) transmission loss is a key requirement when fabricating GaN-on-Si RF devices. To get a better insight into the RF loss mechanism in the GaN-on-Si structure, the RF loss of an AlN/Si template is investigated by varying the growth temperature of AlN during a metalorganic chemical vapor deposition process. The results show that the RF loss of the AlN/Si template is dominated by the interface loss due to the p-type conductive channel at the AlN/Si interface, which is induced by the thermal diffusion of Al during the high-temperature growth. Although a low growth temperature of the AlN nucleation layer can suppress the RF loss in the AlN/Si template, it results in a low crystalline quality of AlN for practical use. Optimizing the growth temperature of the AlN nucleation layer is essential to obtain a good balance between the crystalline quality, morphological quality, and RF loss such that the AlN/Si template is suitable for epitaxial growth of the complete GaN-on-Si RF device structure.