Understanding the Leakage Mechanisms and Breakdown Limits of Vertical GaN-on-Si p⁺n⁻n Diodes: The Road to Reliable Vertical MOSFETs

• Main Authors: Kalparupa Mukherjee, Carlo De Santi, Matteo Buffolo, Matteo Borga, Shuzhen You, Karen Geens, Benoit Bakeroot, Stefaan Decoutere, Andrea Gerosa, Gaudenzio Meneghesso, Enrico Zanoni, Matteo Meneghini
• Format: Article
• Language: English
• Published: MDPI AG 2021-04-01
• Series: Micromachines
• Subjects: semi-vertical; vertical; GaN; pn diodes; leakage modeling; device modeling
• Online Access: https://www.mdpi.com/2072-666X/12/4/445

This work investigates p⁺n⁻n GaN-on-Si vertical structures, through dedicated measurements and TCAD simulations, with the ultimate goal of identifying possible strategies for leakage and breakdown optimization. First, the dominant leakage processes were identified through temperature-dependent current–voltage characterization. Second, the breakdown voltage of the diodes was modelled through TCAD simulations based on the incomplete ionization of Mg in the p⁺ GaN layer. Finally, the developed simulation model was utilized to estimate the impact of varying the p-doping concentration on the design of breakdown voltage; while high p-doped structures are limited by the critical electric field at the interface, low p-doping designs need to contend with possible depletion of the entire p-GaN region and the consequent punch-through. A trade-off on the value of p-doping therefore exists to optimize the breakdown.