LOW FREQUENCY NOISE IN GALLIUM NITRIDE FIELD EFFECT TRANSISTORS

We report on experimental study of the low frequency noise in GaN-based Field Effect Transistors. In both GaN Metal Semiconductor Field Effect Transistors (MESFETs) and AlGaN/GaN Heterostructure Field Effect Transistors (HFETs), the main noise sources are located in the channel. Gate voltage dependence of noise in MESFETs complies with the Hooge formula and indicates the bulk origin of noise. The dependencies of the Hooge parameter, α, on sheet electron concentration ns in HFETs are extracted from measured drain current fluctuations taking into account the contact resistance, and the resistance of the ungated regions of the transistors. At low channel concentrations α is inversely proportional to ns (α ~ 1/ns). This dependence as well as the temperature dependence of noise might be explained by electron tunneling from the 2D gas into the traps in the bulk GaN or AlGaN.