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

Low frequency noise has been investigated in gallium nitride/gallium-alumin um nitride GaN/GaAlN field effect transistors grown on sapphire and silicon carbide (SiC) substrates under identical conditions. GaN/AlGaN heterostruc tures grown on SiC substrate have a lower level of 1/f noise and a higher e lectron mobility compared to samples grown on sapphire. The noise of the ga te leakage current I-g can give the main contribution to the output noise o f the drain current I-d even at I-g/I-d ratios as small as 10(-4)-10(-5). F or the structures grown on SiC, a very weak temperature dependence of the l ow frequency noise was found in the temperature range 300 < T < 550 K. For the structures grown on sapphire, the contribution of generation-recombinat ion noise of the local level with energy activation Delta E = 0.42 eV becam e important at T > 320 K. The effect of band-to-band illumination on the lo w-frequency noise is similar to that for silicon and gallium arsenide (GaAs ) based transistors. The Hooge parameter alpha for the wafers grown on SiC can be as small as alpha = 10(-4). This value of alpha is comparable with t he value of alpha for commercial GaAs field effect transistors. (C) 2000 Am erican Institute of Physics. [S0021-8979(00)02904-2].