Low-frequency noise in surface-treated AlGaN/GaN HFETs

We investigated the 1/f noise generation mechanism in surface-treated AlGaN/GaN heterojunction field-effect transistors (HFETs) with different gate length and gate-to-drain distance (Lgd). From the normalized drain current power spectral density (PSD) SIdId2 versus Id, the AlGaN/GaN HFET with shorter gate length exhibited the Hooge mobility fluctuation (HMF) in subthreshold region and the carrier number fluctuation (CNF) above threshold gate voltage. On the other hand, the HFET with longer gate of 20 μm followed the correlated mobility fluctuation (CMF), irrespective of the gate bias. The extracted trap density (Nt) in the HFET with shorter gate length was noticeably less than that in the HFET with longer length. The input gate voltage power spectral density (PSD) proves that the HFET with shorter gate length suffers from higher interface roughness scattering.