Bias dependence of LF drain and gate noise in GaN HEMTs

Abstract

In this paper, we present some results on low frequency noise of GaN HEMTs grown either on sapphire, SiC or Si. The evolution of LF drain and gate current noise is analysed in ohmic and saturation regime. Devices on sapphire grown either by MOCVD or by MBE present α_H value in ohmic regime as low as 10^-4, whereas for devices grown by MOCVD on SiC, α_H extends from 5x10^-4 to 10^-2. Low frequency gate current noise and coherence function have been measured to discuss possible correlation between drain and gate current noise. Devices with high reverse gate current exhibit high gate current noise. The coherence function increases when the I_g/I_d ratio becomes higher than 10^-5 which results in increase of the drain current noise due to contribution of gate current fluctuations.