ZnO is known as a semiconductor tolerant to extremely high doping levels. So far, most of the efforts have focused on the development of transparent conducting oxides for flat panel or photovoltaic industry. Only very recently, it has been realized that this feature might be exploited for plasmonics in the infrared spectral range. By using advanced growth techniques, semiconductors might outperform traditional metals in terms of tuneability and flexibility in device fabrication and could provide better plasmonic performance.
Using Molecular Beam Epitaxy, we are able to fabricate n-type ZnO:Ga films with high structural quality up to Ga mole fractions of about 7.0 %, reaching free-carrier concentrations of more than 8 x 1020 cm-3. Controlling the doping levels allows for tuning of the positive-to-negative crossover wavelength of the real part of the resultant metallic dielectric function (λC) from the mid infrared up to about 1.2 Ám.
The surface plasmon polariton (SPP) dispersion at the air/ZnO:Ga interface can be tuned via the doping level in a wide spectral range from the midinfrared up to the telecommunication wavelength band at about 1.55 Ám. This allows us to adjust the SPP frequency resonantly to molecular vibrations, band edge related transitions of quantum dots (e.g., PbS) or transitions of other infrared emitters like Er+3 ions.
Furthermore, we fabricate ZnO:Ga multilayer structures with well-defined doping levels as well as smooth interfaces and investigate their plasmonic properties. In particular, we focus on engineering of the dispersion relation of SPPs at metal/metal-interfaces and of coupled SPPs in multi-layer structures for nanophotonic manipulation of infrared light, even at telecommunication wavelengths.
letzte Änderung: 21.09.2015 id