Proposal and Performance Analysis of Normally Off $ \hbox{n}^{++}$ GaN/InAlN/AlN/GaN HEMTs With 1-nm-Thick InAlN Barrier
Year: 2010
Type: article
Abstract: Design considerations and performance of n++GaN/InAlN/AlN/GaN normally off high-electron mobility transistors (HEMTs) are analyzed. Selective and damage-free dry etching of the gate recess through the GaN cap down to a 1-nm-thick InAlN barrier secures positive threshold voltage, while the thickness and the doping of the GaN cap influence the HEMT direct current and microwave performance. The cap doping density was suggested to be 2 × 1020cm-3. To screen the channel from the surface traps, the needed cap thickness was estimated to be only 6 nm. Design is proved by an experiment showing a constant value of the HEMT dynamical access resistance, while a single-pulse experiment indicated almost collapse-free performance. On the other hand, it is found that the n++GaN cap does not contribute to the HEMT drain current conduction, nor does it provide a path for the off-state breakdown. HEMTs with a gate length of 0.25 μm and a 4-μm source-to-drain distance show a drain-to-source current of 0.8 A/mm, a transconductance of 440 mS/mm, a threshold voltage of ~0.4 V, and a cutoff frequency of 50 GHz. A thin and highly doped GaN cap is also found to be suitable for the processing of normally on HEMTs by adopting the nonrecessed gate separated from the cap by insulation.
Authors: Jan Kuzmik, Clemens Ostermaier, G. Pozzovivo, Bernhard Basnar, Werner Schrenk, Jean-François Carlin, M. Gonschorek, Eric Feltin, Nicolas Grandjean, Y. Douvry, Christophe Gaquiere, Jean-Claude De Jaeger, K. Cico, Karol Frohlich, J. Skriniarova, Jaroslav Kovac, Gottfried Strasser, Dionyz Pogany, Erich Gornik
Institutions: TU Wien, Slovak Academy of Sciences, Institute of Electrical Engineering of the Slovak Academy of Sciences, Infineon Technologies (Austria), École Polytechnique Fédérale de Lausanne, Institut d'Electronique, de Microélectronique et de Nanotechnologie, Slovak University of Technology in Bratislava
Language: English
Subfield: Condensed Matter Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2097322384