On/off-state noise characteristics in AlGaN/GaN HFET with AlN buffer layer

Abstract

The AlGaN/GaN heterojunction field-effect transistor (HFET) with an AlN buffer layer (the proposed device) was fabricated, and its noise performances were investigated compared to the conventional AlGaN/GaN HFET with a GaN buffer layer (the reference device). Both devices with a gate length of 0.5 mu m demonstrated 1/f noise properties with carrier number fluctuations channel mechanism, regardless of the buffer layer. The proposed device had higher off-state leakage current and larger trap density (N-t) than those of the reference device because of the partially strained GaN (83% relaxed GaN) channel grown on a AlN buffer layer. However, the noise measurements at off-state proved that the generation-recombination (g-r) noise is absent in the proposed device due to the AlN buffer layer with high bandgap energy (E-g = 6.2 eV), whereas the reference device suffers from the g-r noise in the GaN buffer layer.