High linearity and low RF loss GaN-on-Si substrates achieved through interface engineering

Abstract

GaN-on-Si HEMTs are emerging as a leading candidate for 5 G and FR3 6G RF front-end modules. Conductive losses in the Si substrate, especially at the high resistivity Si and III-N epitaxial layer interface, degrade the power amplifier and switch performance. This parasitic conduction also causes harmonic distortion degrading switch linearity. We demonstrate that substrate RF properties such as high effective resistivity and low harmonic distortion can be achieved through interface engineering during III-N layer epitaxy and 2nd harmonic power (H2) of <-85 dBm can be achieved with a corresponding effective resistivity of >7kΩ⋅cm. Furthermore, the evolution of substrate linearity with temperature and bias for samples grown with varied AlN nucleation layer growth conditions was studied and a H2<−88 dBm was measured on HEMTs stacks at 125° C.