Experimental results of the low-frequency noise measurements on a large num
ber of different AlGaN/GaN High Electron Mobility Transistors (HEMTs) grown
on sapphire and SIC substrates have been presented. In the HEMTs grown on
sapphire, the 1/f noise is an order of magnitude (or more) higher than for
AlGaN/GaN HEMTs grown on SiC substrates. The devices on SIC substrates also
have higher electron mobility compared to the devices grown on sapphire su
bstrates. The temperature dependence of noise reveals a contribution to the
noise from a local level with activation energy of approximately 0.42 eV f
or the structures grown on sapphire. A very weak temperature dependence of
the low-frequency 1/f noise found for the wafers grown on SiC is very impor
tant for high temperature applications of these devices.