Low-frequency noise in AlGaN/GaN heterojunction field effect transistors on SiC and sapphire substrates

Abstract

Low frequency noise has been investigated in gallium nitride/gallium–aluminum nitride GaN/GaAlN field effect transistors grown on sapphire and silicon carbide (SiC) substrates under identical conditions. GaN/AlGaN heterostructures grown on SiC substrate have a lower level of 1/f noise and a higher electron mobility compared to samples grown on sapphire. The noise of the gate leakage current Ig can give the main contribution to the output noise of the drain current Id even at Ig/Id ratios as small as 10−4–10−5. For the structures grown on SiC, a very weak temperature dependence of the low frequency noise was found in the temperature range 300<T<550 K. For the structures grown on sapphire, the contribution of generation–recombination noise of the local level with energy activation ΔE=0.42 eV became important at T>320 K. The effect of band-to-band illumination on the low-frequency noise is similar to that for silicon and gallium arsenide (GaAs) based transistors. The Hooge parameter α for the wafers grown on SiC can be as small as α=10−4. This value of α is comparable with the value of α for commercial GaAs field effect transistors.