A cost-effective technology to improve power performance of nanoribbons GaN HEMTs

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Abstract
A cost-effective fabrication process is developed to improve the power performance of AlGaN/GaN High Electron Mobility Transistors (HEMTs). This process uses nitrogen ion (N+) implantation to form multiple parallel nanoribbons on AlGaN/GaN heterostructures, with a thin buffer layer (AlGaN/GaN NR-HEMTs). The stopping and range of ions in matter simulations of the N+ implantation combined with measured current-field characteristics reveal a good electrical isolation beneath the two-dimensional electron gas, resulting in substantial increase in the breakdown field of the NR-HEMTs, when compared to conventional AlGaN/GaN HEMTs. The fabricated AlGaN/GaN NR-HEMTs performed (i) an ON/OFF current ratio more than two orders of magnitude larger and (ii) a buffer leakage current more than one order of magnitude weaker than that of the conventional AlGaN/GaN HEMTs. The on-resistance, RON, and series resistance, RS, of AlGaN/GaN NR-HEMTs are both reduced by one order of magnitude when compared to those of the conventional AlGaN/GaN HEMTs. These have boosted the drive current density by up to 435%. Furthermore, we have found that the architecture of the AlGaN/GaN NR-HEMTs reduces the destructive impact of electron traps in the device. An optimized AlGaN/GaN NR-HEMT exhibited a better electrostatic integrity, a subthreshold slope of ∼210 mV/dec instead of 730 mV/dec for a conventional GaN HEMT. A higher linearity in the transconductance, gm, of NR-HEMTs is observed, twice of that of a conventional GaN HEMT. These results demonstrate the great interest of developed process technology of NR-HEMTs for high-power switching applications.

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