Out-diffusion of Pd as part of degradation mechanisms in RF AlGaN-GaN HEMTs with Ni-Pd-Au Schottky contacts: part II

Yongkun Sin; Dmitry Veksler; William Hubbard; Scott Sitzman; Miles Brodie; Zachary Lingley; Neil Ives

doi:10.1117/12.2576910

5 March 2021 Out-diffusion of Pd as part of degradation mechanisms in RF AlGaN-GaN HEMTs with Ni-Pd-Au Schottky contacts: part II

Yongkun Sin, Dmitry Veksler, William Hubbard, Scott Sitzman, Miles Brodie, Zachary Lingley, Neil Ives

Author Affiliations +

Proceedings Volume 11686, Gallium Nitride Materials and Devices XVI; 116862A (2021) https://doi.org/10.1117/12.2576910
Event: SPIE OPTO, 2021, Online Only

Abstract

GaN high electron mobility transistors (HEMTs) on SiC substrates are produced for both commercial and defense applications that require high voltage, high power, and high efficiency operation. Although leading GaN HEMT manufacturers have reported excellent RF power characteristics and encouraging reliability, long-term reliability in the space environment remains a major concern due to unknown degradation mechanisms. For the present study, we continued to investigate degraded RF GaN HEMTs using micro-analytical techniques. Our RF AlGaN-GaN devices grown on SiC substrate had a Ni-Pd-Au Schottky gate length of 0.25 μm, a total gate width of 6 × 150 μm periphery, and a field plate. First, we performed DC bias-temperature stress tests on GaN HEMTs and some GaN HEMTs were thermally stressed as control samples. Second, we employed focused ion beam (FIB) to prepare TEM cross sections from degraded and control devices for defect analysis using a high resolution TEM. Pits, cracks, and pockets of palladium were found at the edge of the drain side of the gate. We report our detailed analysis results including our understanding on the out-diffusion of Pd as a potential degradation mechanism in our RF GaN HEMTs.

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Yongkun Sin, Dmitry Veksler, William Hubbard, Scott Sitzman, Miles Brodie, Zachary Lingley, and Neil Ives "Out-diffusion of Pd as part of degradation mechanisms in RF AlGaN-GaN HEMTs with Ni-Pd-Au Schottky contacts: part II", Proc. SPIE 11686, Gallium Nitride Materials and Devices XVI, 116862A (5 March 2021); https://doi.org/10.1117/12.2576910

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