S. Rumyantsev et al., Low-frequency noise in AlGaN/GaN heterojunction field effect transistors on SiC and sapphire substrates, J APPL PHYS, 87(4), 2000, pp. 1849-1854
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].