Plasmonische Strukturen auf Ge-Photodioden zur Integration von kollinearen Biosensoren

Die Arbeit betrachtet unterschiedliche integrierte kollineare refraktive plasmonische Sensoren auf der Basis von Ge-Photodioden. Die plasmonischen Strukturen werden dabei in silizium-kompatibler Technologie direkt auf der Photodiode realisiert. Anhand des Herstellungsablaufs und elektro-optischer Messungen wird die Eignung der einzelnen Konzepte hinsichtlich der Anwendbarkeit in der refraktiven Biosensorik diskutiert

Integrated collinear refractive index sensor with Ge PIN photodiodes

Refractive index sensing is a highly sensitive and label-free detection method for molecular binding events. Commercial implementations of biosensing concepts based on plasmon resonances typically require significant external instrumentation such as microscopes and spectrometers. Few concepts exist that are based on direct integration of plasmonic nanostructures with optoelectronic devices for on-chip integration. Here, we present a CMOS-compatible refractive index sensor consisting of a Ge heterostructure PIN diode in combination with a plasmonic nanohole array structured directly into the diode Al contact metallization. In our devices, the photocurrent can be used to detect surface refractive index changes under simple top illumination and without the aid of signal amplification circuitry. Our devices exhibit large sensitivities > 1000 nm per refractive index unit in bulk refractive index sensing and could serve as prototypes to leverage the cost-effectiveness of the CMOS platform for ultra-compact, low-cost biosensors.Comment: 21 pages, 6 figures, supporting information with 11 pages and 11 figures attache

Ge(Sn) nano-island/Si heterostructure photodetectors with plasmonic antennas

We report on photodetection in deep subwavelength Ge(Sn) nano-islands on Si nano-pillar substrates, in which self-aligned nano-antennas in the Al contact metal are used to enhance light absorption by means of local surface plasmon resonances. The impact of parameters such as substrate doping and device geometry on the measured responsivities are investigated and our experimental results are supported by simulations of the three-dimensional distribution of the electromagnetic fields. Comparatively high optical responsivities of about 0.1 A W−1 are observed as a consequence of the excitation of localized surface plasmons, making our nano-island photodetectors interesting for applications in which size reduction is essential