Low-Frequency Noise Caused by Substrate Current in AlGaAs/InGaAs HEMTs

The surplus low-frequency noise (LFN) caused by substrate current is investigated for high electron mobility transistors (HEMTs). The substrate current increases with decreasing the substrate thickness, which causes the surplus LFN. It is found that the surplus LFN is proportional to the square of the substrate current, and becomes dominant in the case of a thinner substrate. We also discuss the restriction on the substrate thickness from the viewpoint of LFN.