Contactless electroreflectance studies of the Fermi level position at the air/GaN interface: Bistable nature of the Ga-polar surface
| Autor: | M. Sobanska, Zbigniew R. Zytkiewicz, Jan Misiewicz, Robert Kudrawiec, Łukasz Janicki, Marta Gladysiewicz, K. Klosek, Pawel Kempisty |
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| Rok vydání: | 2017 |
| Předmět: |
Materials science
General Physics and Astronomy Gallium nitride 02 engineering and technology 01 natural sciences Condensed Matter::Materials Science symbols.namesake chemistry.chemical_compound Condensed Matter::Superconductivity Electric field 0103 physical sciences 010302 applied physics Condensed matter physics business.industry Fermi level Doping Surfaces and Interfaces General Chemistry 021001 nanoscience & nanotechnology Condensed Matter Physics Surfaces Coatings and Films Band bending Semiconductor chemistry symbols Density of states Optoelectronics Condensed Matter::Strongly Correlated Electrons Density functional theory 0210 nano-technology business |
| Zdroj: | Applied Surface Science. 396:1657-1666 |
| ISSN: | 0169-4332 |
| DOI: | 10.1016/j.apsusc.2016.12.013 |
| Popis: | In this paper we show that the surface Fermi level of Ga-polar GaN exhibits a bistable behavior allowing it to be located at two distinct energetic positions at the air/GaN interface which is unusual for other III–V semiconductors such as GaAs or GaSb. To determine the Fermi level position at the air/GaN interface we perform contactless electroreflectance measurements on specially designed UD+ structures [GaN(undoped)/GaN(highly doped)/substrate] doped by Si and Mg. Analyzing the period of Franz-Keldysh oscillation we determine the built-in electric field in the undoped (U) layer. These studies coupled with numerical solutions of the Poisson equation allowed us to determine the position of the Fermi level at the air/GaN interface. We observe a change in the band bending correlated to different Fermi level positions in the doped (D+) layer. We show that depending on the doping type in the D+ layer the Fermi level at the air/GaN interface is located in the upper or lower singularity of surface density of states (SDOS) for Si or Mg doping of D+ layer, respectively. We support our findings with the density functional theory calculations of the SDOS and the dependence of the Fermi level position on the doping concentration in the bulk of a GaN slab. |
| Databáze: | OpenAIRE |
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