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Effect of Insertion of Ultrathin Al 2 O 3 Interlayer at Metal/GaN Interfaces
Author(s) -
Akazawa Masamichi,
Hasezaki Taito
Publication year - 2018
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.201700382
Subject(s) - materials science , schottky barrier , work function , metal , schottky diode , electrode , epitaxy , layer (electronics) , semiconductor , diode , heterojunction , optoelectronics , condensed matter physics , nanotechnology , chemistry , metallurgy , physics
Fermi level depinning at a metal/semiconductor interface by using an ultrathin insulating interlayer to block the penetration of the metal wave function into the semiconductor is examined on GaN. A Si‐doped n‐type GaN epitaxial layer on a freestanding GaN substrate is used as the host material. For the samples with an interlayer, an ultrathin Al 2 O 3 layer of 1 nm thickness is deposited by atomic layer deposition. As the metal layers, Ag, Cu, Au, Ni, and Pt are deposited by electron beam evaporation. Samples without an interlayer are also fabricated for comparison. The apparent change in current–voltage characteristics of the Schottky barrier diodes with the insertion of the interlayer is dependent on the electrode metal. However, the apparent Schottky barrier height (SBH) for the samples with the interlayer is almost constant and independent of the metal electrode, although the samples without an interlayer exhibit a moderate dependence of the SBH on the metal work function. Thus, the pinning becomes stronger upon the insertion of the interlayer, although blocking of the metal wave function by using an ultrathin insulator is expected to lead to depinning.