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The impact of the short gate length on the drain current and low frequency (LF) noise in GaN/AlGaN metal-oxide-semiconductor high-electron-mobility field-effect-transistors has been studied. In some short devices, a parasitic subthreshold current is observed. In this article, the origin of parasitic subthreshold currents were explored using LF noise and trapping transient measurements. The LF noise power spectral density (PSD) of the devices without parasitic drain current decreased monotonically with the decrease of the drain current, while the PSD of the device with the parasitic drain current strongly increased for lower drain current. The 1/f1.5 noise corresponding with the parasitic leakage can be explained by the level broadening of generation-recombination centers in the GaN channel. This is confirmed by the trapping transient measurements, revealing a temperature-independent time constant, associated with the leakage path in short channel transistors, exhibiting the subthreshold humps. [ABSTRACT FROM AUTHOR]

In this article, GaN/AlGaN metal–oxide–semiconductor high-electron-mobility field-effect transistors (MOSHEMTs) fabricated on high-resistivity Si (111) substrates have been evaluated using low-frequency (LF) noise measurement. The noise power spectral density (PSD) of devices with different lengths and channel orientations has been characterized in linear operation. No noticeable differences in the electrical and noise PSD characteristics have been observed between the GaN [1100] and [1120] channel orientations. While most devices are dominated by 1/ƒ noise, originating from number fluctuations, for long devices (L ≥ 1.1~μm), additional generation–recombination (GR) noise has been observed, originating from traps in the GaN layer. [ABSTRACT FROM AUTHOR]