Contactless electroreflectance studies of the Fermi level position at the air/GaN interface: Bistable nature of the Ga-polar surface
PBN-AR
Instytucja
Instytut Wysokich Ciśnień Polskiej Akademii Nauk
Informacje podstawowe
Główny język publikacji
angielski
Czasopismo
Applied Surface Science (35pkt w roku publikacji)
ISSN
0169-4332
EISSN
Wydawca
ELSEVIER SCIENCE BV
DOI
URL
Rok publikacji
2017
Numer zeszytu
Strony od-do
1657-1666
Numer tomu
396
Identyfikator DOI
Liczba arkuszy
1,8
Słowa kluczowe
angielski
Gallium nitride
Fermi level
Surface potential
Contactless electroreflectance
Streszczenia
Język
angielski
Treść
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.
Inne
System-identifier
PX-5a8ea508d5dee0db7bca4dfa
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