Excess low-frequency noise in AlGaN/GaN-based high-electron-mobility transistors

The low-frequency 1/f noise characteristics of AlGaN/GaN high-electron-mobility transistors with gate length scaled down to 150 nm grown on sapphire by metalorganic chemical vapor deposition have been studied. Certain features of the 1/f noise have been revealed in these short-gate transistors. The low-frequency noise spectra show drastically different behavior depending on the gate voltage V-G in the range of low (V(Gt)less than or equal toV(G)less than or equal to0) and high (V-G<V-Gt) biases. The noise spectra-gate bias dependences allow one to distinguish a spatial redistribution of effective noise sources in the transistor channel. The Hooge parameter has been deduced separately for the ungated region, alpha(H)(p)similar or equal to10(-3), and for the gated region, alpha(H)(a)similar or equal to2x10(-4), of the transistor channel. These values are as low as those previously observed in nitride heterostructures grown on silicon carbide substrates. (C) 2002 American Institute of Physics.