Free‐electron concentration and polarity inversion domains in plasmonic (Zn,Ga)O

Abstract

Heavily Ga‐doped ZnO layers are grown on bulk ZnO wafers by molecular beam epitaxy. The layers grow in a two‐dimensional pseudomorphic mode with high structural quality under increase of the c‐lattice constant up to free‐electron concentrations of 1021cm−3. Formation of Zn‐polar inversion domains in the O‐polar ZnO matrix is identified as the limiting factor for the incorporation of electrically active Ga. The domain formation can be inhibited by growing with larger excess of Zn. This results in a shift of surface plasmon frequency of ℏΔω=100 meV and allows for covering the telecommunication wavelength range.

Influence of polarity inversion on the electrical properties of Ga‐doped ZnO thin films

“…The influence of polar face on growth of GZO films has been reported on single crystalline ZnO substrates . While the GZO layer is expected to keep its polarity for the Zn‐polar face, the polarity can be flipped in the case of O‐polar face . It is well known that the effectiveness of incorporating a dopant into ZnO strongly depends on the polarity , and so using the intensity ratio between Ga 2p and Zn 2p core HE‐XPS spectra, we confirmed that the Ga content of GZO films on O‐polar ZnO is relatively higher than those on the Zn‐polar face.…”

“…The influence of polar face on growth of GZO films has been reported on single crystalline ZnO substrates . While the GZO layer is expected to keep its polarity for the Zn‐polar face, the polarity can be flipped in the case of O‐polar face .…”

Transparent conducting oxides for electro-optical plasmonic modulators

“…AZO: Aluminum-doped zinc oxide; GZO: Gallium-doped zinc oxide; ITO: Indium tin oxide. tivity for ITO [59,69], AZO [59,[69][70][71][72], GZO [59,70,73,74], and indium oxide doped with both tin and zinc (ZITO, ITZO) [69]; (ii) SPP guiding in ITO [69,[75][76][77], AZO, and GZO [77]; (iii) tunability of localized surface plasmon resonance (LSPR) in colloidal nanocrystals of ITO [78,79], AZO [80], and indium-doped cadmium oxide (ICO) [81]; (iv) LSPR in ITO nanorods and an increase of the electron concentration in the conduction band [82,83]; (v) LSPR [77,84] or SPP guiding [85] with pattern films; and (vi) negative refraction [86] as well as near-perfect absorption in multilayer structures with ZnO components [87]. Theoretical studies of GZO [88] and first-principle theoretical calculations of optical properties of AZO [89] were reported as well.…”