Proton Radiation-Induced Void Formation in Ni/Au-Gated AlGaN/GaN HEMTs

• Published in: IEEE electron device letters 2014-12, Vol.35 (12), p.1194-1196
• Main Authors: Koehler, Andrew D., Hobart, Karl D., Weatherford, Todd R., Kub, Francis J., Specht, Petra, Anderson, Travis J., Weaver, Bradley D., Greenlee, Jordan D., Tadjer, Marko J., Porter, Matthew, Wade, Michael, Dubon, Oscar C.
• Format: Article
• Language: English
• Subjects: Aluminum gallium nitride; defect; Gallium nitride; GaN HEMT; HEMTs; Nickel; nickel void; proton irradiation; Proton radiation effects; Reliability; schottky gate
• ISSN: 0741-3106; 1558-0563
• DOI: 10.1109/LED.2014.2363433

AlGaN/GaN high-electron mobility transistors (HEMTs) were exposed to 2-MeV protons irradiation, at room temperature, up to a fluence of 6 × 10 14 H + /cm 2 . Aside from degradation resulting from radiation-induced charge trapping, transmission electron microscopy and electrical measurements reveal a radiation-induced defect located at the edges of the Ni/Au Schottky gate in the proton-irradiated devices. At the edges of the Ni/Au gate, the Ni of the Ni/Au gate diffused up into the Au layer and migrated into the AlGaN barrier, leaving voids in the Ni layer at the gate edges after irradiation. These radiation-induced voids are caused by diffusion of Ni through vacancy exchange, known as the Kirkendall effect, resulting in reduced gate area and degrading the HEMT performance.