Ultra-thin plasmonic detectors

Abstract

Plasmonic materials, and their ability to enable strong concentration of optical fields, have offered a tantalizing foundation for the demonstration of sub-diffraction-limit photonic devices. However, practical and scalable plasmonic optoelectronics for real world applications remain elusive. In this work, we present an infrared photodetector leveraging a device architecture consisting of a “designer” epitaxial plasmonic metal integrated with a quantum-engineered detector structure, all in a mature III-V semiconductor material system. Incident light is coupled into surface plasmon-polariton modes at the detector/designer metal interface, and the strong confinement of these modes allows for a sub-diffractive ( ∼ λ 0 / 33 ) detector absorber layer thickness, effectively decoupling the detector’s absorption efficiency and dark current. We demonstrate high-performance detectors operating at non-cryogenic temperatures ( T = 195 K ), without sacrificing external quantum efficiency, and superior to well-established and commercially available detectors. This work provides a practical and scalable plasmonic optoelectronic device architecture with real world mid-infrared applications.

High operating temperature plasmonic infrared detectors

“…Moreover, MCT materials are facing increased restrictions, including being banned in European markets, due to environmental concerns associated with mercury and cadmium 2 . For this reason there has been historical, and increasing, interest in developing alternative materials and architectures, specifically in the III-V semiconductor family, for LWIR detection 1,3 .…”

“…The current and long-time stateof-the-art LWIR detector is the HgCdTe (MCT) photodetector. MCT detectors, in addition to suffering the same hightemperature challenges as any LWIR detector, rely on the epitaxial growth of II-VI alloys, for which uniform growth is notoriously difficult, especially for the high Hg-content HgCdTe alloys required for LWIR detection 1 . Moreover, MCT materials are facing increased restrictions, including being banned in European markets, due to environmental concerns associated with mercury and cadmium 2 .…”

“…However, T2SL detectors have struggled to meet predicted performance metrics, in part a result of short minority carrier lifetimes 6 and/or low absorption coefficients 7 . One increasingly attractive approach to overcoming the poorer performance of T2SL-based detectors has been to leverage detector architectures which enhance the optical fields in the detector [8][9][10][11][12][13][14][15][16] to increase detector absorption while maintaining small detector volumes, and therefore low a) Author to whom correspondence should be addressed: nordin@utexas.edu dark currents.…”

“…A particularly successful implementation of opticallyenhanced T2SL detectors is the recently-demonstrated ultrathin (t ∼ λ 0 /30) plasmonic detector 15 , which realizes responsivities commensurate with much thicker traditional detectors (t ∼ λ 0 ), while also demonstrating dark currents substantially below "Rule 07" 17 , the heuristic for HgCdTe detectors and thus a useful benchmark for competing detector technologies. In such an architecture, an ultra-thin (∼ 311 nm) T2SL detector structure is grown upon a heavily (n ++ ) doped semiconductor 'ground-plane'.…”

“…Figure 1(b) shows rigorous coupled wave analysis 20 (RCWA) simulations of plasmonic detector external quantum efficiency (EQE) for absorber cutoff wavelengths from 9 µm to 14 µm. For these simulations, we use a complex uniaxial permittivity tensor for the T2SL 21 with ε || obtained from our previous work 15 and ε ⊥ = 12.56. As can be seen in Fig.…”