Field- and current-driven degradation of GaN-based power HEMTs with p-GaN gate: Dependence on Mg-doping level. (September 2017)

• Record Type: Journal Article
• Authors: Rossetto, I.; Meneghini, M.; Canato, E.; Barbato, M.; Stoffels, S.; Posthuma, N.; Decoutere, S.; Tallarico, A.N.; Meneghesso, G.; Zanoni, E.
• Is Part Of: Microelectronics and reliability. Volume 76/77(2017)
• Page Start: 298
• Page End: 303
• Publication Date: 2017-09
• Subjects: GaN HEMT -- p-GaN gate -- Transmission line pulse (TLP) -- Long-term reliability; Electronic apparatus and appliances -- Reliability -- Periodicals; Miniature electronic equipment -- Periodicals; Appareils électroniques -- Fiabilité -- Périodiques; Équipement électronique miniaturisé -- Périodiques; Electronic apparatus and appliances -- Reliability; Miniature electronic equipment; Periodicals; 621.3815
• DOI: 10.1016/j.microrel.2017.06.061
• Languages: English
• ISSNs: 0026-2714

Abstract

Abstract: Within this paper we investigate the degradation of GaN-HEMTs with p-GaN gate submitted to stress at forward gate bias. We studied the effect of both constant-voltage stress and short-pulse stress (induced by TLP, Transmission Line Pulser); devices having three different Mg-doping levels (ranging from 2.1 · 10 19 /cm 3 to 2.9 · 10 19 /cm 3 ) were used for the study. We demonstrated the existence of two different degradation mechanisms, depending on the stress conditions: (i) when submitted to TLP stress (100 ns pulses with increasing amplitude), the failure occurs through a field-driven process, i.e. the breakdown of the metal/p-GaN Schottky junction, which is reversely biased when the gate is at positive voltage. Failure voltage decreases with increasing Mg doping, since higher acceptor levels result in a higher electric field. (ii) Conversely, during constant-voltage stress, the long-term stability is undermined by a current-driven process, namely the accumulation of positive charges at the p-GaN/AlGaN interface, which promotes an increase of the leakage current, first gradual and then catastrophic. Increasing Mg-concentration in the p-GaN results in a reduction of the gate leakage at high forward gate bias. As a consequence, devices with higher Mg doping have long TTF (more than two orders of magnitude with respect to the samples with lower Mg doping). Highlights: Impact of Mg doping concentration on the robustness toward forward gate bias in HEMTs with p-GaN gate. TLP stress induces a field-driven failure mechanisms; long-term reliability is undermined by a current-driven process. Robustness under TLP stress decreases with the increase of Mg doping. Long-term stability improves with the increase of Mg doping. Time to failure (long-term stability) is Weibull distributed and well-correlated to initial leakage current.