1/f noise characteristics of AlGaN/GaN HEMTs with periodically carbon-doped GaN buffer layer

Abstract

We investigate the DC and 1/f noise properties in Al0.25Ga0.75N/GaN high-electron mobility transistors (HEMTs) with two types of 2 pm-thick periodically carbon-doped GaN buffer layer (PC-doped GaN buffer) with and without inserting the 30 nm-thick Al0.05Ga0.95N back barrier layer between the GaN channel layer and the PC doped GaN buffer. The PC-doped GaN buffer layer consists of multiple layers of 12 nm-thick C-doped GaN layer with doping concentration of 1 x 10(18) cm(-3) and 50 nm-thick undoped GaN layer with unintentional n-typing concentration of 2 x 10(16) cm(-3). A reference AlGaN/GaN HEMT with 2 pm-thick highly-resistive GaN buffer layer without C-doping is also fabricated for comparison. Similarly to the reference AlGaN/GaN HEMT, the AlGaN/GaN HEMTs with PC-doped GaN buffer show typical 1/f noise characteristics mainly due to the trapping effects at the AlGaN/GaN interface from subthreshold region to strong-accumulation region, which indicates that the deep trapping effects in the PC-doped GaN buffer layer is negligible, and experience the correlated mobility fluctuations (CMF), which is convinced from the drain current power spectral density (PSD) versus drain current. At off-state (deep-subthreshold region), on the other hand, the HEMTs with the PC-doped GaN buffer layer exhibit 1/f(2) noise characteristics, which are closely related to the generation-recombination (g-r) noise caused by the spatial trapping/detrapping process between the deep acceptor in the C-doped layer and the shallow donor in the undoped layer in the PC-doped GaN buffer, while the reference HEMT still shows typical 1/f noise characteristics.