Contribution of Substrate Harmonic Distortion to GaN-on-Si RF Switches Linearity

Cardinael, Pieter [UCL] Yadav, Sachin [imec] Rack, Martin [UCL] Peralagu, Uthayasankaran [imec] Alian, Alireza [imec] Parvais, Bertrand [imec, VUB] Collaert, Nadine [imec] Raskin, Jean-Pierre [UCL] et al.[show all]

We demonstrate high linearity of fully processed GaN on 2-mm high resistivity (HR) Si wafers with high effective resistivity ( ρeff> 2 kΩ ⋅ cm). Using two common-gate (MOS-)HEMT devices presenting different levels of distortion as demonstrators, we discuss the impact of substrate-induced harmonic distortion (HD) on RF switches. By comparing switch and CPW line measurements, it is possible to estimate the substrate contribution to HD. For the relatively nonlinear device, the intrinsic device nonlinearities dominate by a 16–20-dB margin over the substrate contribution. For a more linear device (−110 dBc of second harmonic power at 900 MHz and Pin = 15 dBm), the substrate distortion contributes equally to channel nonlinearity, highlighting the necessity of engineering the substrate’s RF performance together with the transistor. We provide guidelines for substrate ρeff to achieve good switch linearity for given device harmonic levels.