Low frequency noise of AlGaN/GaN HEMT grown on Al2O3, Si and SiC substrates

The use of wide bandgap materials for broadcast telecommunication and defense systems allow high power, high efficiency and high integration levels of active devices thanks to their microwave electrical performances. GaN based devices have also demonstrated great potential for high frequency linear low noise applications. However, low frequency noise (LFN) performances characteristics are still under progress as they are related to the material quality and process control. As a consequence, the LFN sources identification and modeling in AlGaN/GaN devices have a twofold stake: on one hand it contributes to the process improvement by the identification of the main noise sources, and on the other hand the nonlinear noisy model can be used for CAD of non linear circuits such as low phase noise oscillators. This study focuses on the confrontation of High Electron Mobility Transistors (HEMT) featuring 0.15x2x50 mu m(2) gate dimension grown by MOCVD on sapphire (Al2O3), silicon (Si) and silicon carbide (SiC) substrates. Each substrate has got its own advantages and drawbacks in terms of cost, wafer size, thermal conductivity and lattice mismatch. This paper deals with the noise mechanisms relative to the use of several substrates: for drat purpose, low frequency noise measurements have been performed under different biasing conditions for each substrate. The contributions of the different noise sources (1/f, generation-recombination centers (GR)....) are discussed for each substrate and related to each technological process.