Polarization Effects of GaN and AlGaN: Polarization Bound Charge, Band Bending, and Electronic Surface States

• Published in: Journal of electronic materials Vol. 43; no. 12; pp. 4560 - 4568
• Main Authors: Eller, Brianna S., Yang, Jialing, Nemanich, Robert J.
• Format: Journal Article
• Language: English
• Published: Boston Springer US 01.12.2014; Springer Nature B.V
• Subjects: Aluminum gallium nitrides; Bend tests; Bending machines; Characterization and Evaluation of Materials; Charge materials; Chemistry and Materials Science; Collapse; Conduction bands; Current leakage; Electron states; Electronic devices; Electronics; Electronics and Microelectronics; Fermi level; Gallium nitrides; Gates; Instrumentation; Materials Science; Nitrogen; Optical and Electronic Materials; Photoelectric emission; Photoelectron spectroscopy; Polarization; Reliability; Solid State Physics; Spectroscopic analysis; Vacancies; surface states; polarization; GaN; AlGaN; band bending
• ISSN: 0361-5235; 1543-186X
• DOI: 10.1007/s11664-014-3383-z

GaN-based devices are currently limited by reliability issues such as gate leakage and current collapse, where the mechanisms responsible for degradation are closely related to the electronic surface state configuration. Therefore, understanding the electronic surface state configuration of GaN-based materials will help improve device performance. Since GaN has an inherent polarization, these materials are also subject to a bound polarization charge, which influences the electronic state configuration. In this study, the surface band bending of N-face GaN, Ga-face GaN, and Ga-face AlGaN was measured with x-ray photoemission spectroscopy after various cleaning steps to investigate the effects of the polarization. Despite the different surface bound charge on these materials, similar band bending was observed regardless of the magnitude or direction of the charge. Specifically, the band bending varied from −0.1 eV to 0.9 eV on these samples, which supported the models of a Fermi level pinning state at ∼0.4 eV to 0.8 eV below the conduction band. Based on available literature, we suggest this pinning state is indirectly evident of a nitrogen vacancy or gallium-dangling bond.