Temperature-dependent investigation of low frequency noise characteristics of mesa-, fin-, and island-isolated AlGaN/GaN HFETs

• We report the low frequency noise performance of two novel AlGaN/GaN technologies.
• We report observed GR signatures in gate and drain noise of island-isolated HFETs.
• A range of relevant time constants is speculated for the island-isolated HFETs.
• We report on superiority of fin-isolation technology over island-isolation.

The low frequency drain and gate noise-current characteristics of AlGaN/GaN heterostructure field effect transistors (HFETs) of two recently proposed isolation-feature topologies are experimentally investigated. In light of this study, suitability of high frequency operation of these technological alternatives is evaluated. These device types include “fin-isolated” (i.e., devices built on fins of size 16 μm × 40 μm), and “island-isolated” (i.e., devices built on an array of islands of size 16 μm × 7 μm). The low frequency noise characteristics of these devices are compared to the traditional “mesa-isolated” HFETs (i.e., devices built on conventional mesas of dimension 70 μm × 100 μm). Whereas generation–recombination (G–R) bulge signatures are absent from the low frequency noise spectra of the mesa- and fin-isolated devices, such features are observed on gate and drain noise-current spectra of island-isolated HFETs. Further exposure of the gate and ohmic electrodes to etched surfaces in island-isolated devices is deemed responsible for emergence of G–R signatures.