Jarrod Vaillancourt

All ink-jet-printed carbon nanotube thin-film transistor on a polyimide substrate with an ultrahigh operating frequency of over 5 GHz

We report a flexible carbon nanotube (CNT) thin-film transistor (TFT) fabricated solely by ink-jet printing technology. The TFT is top gate configured, consisting of source and drain electrodes, a carrier transport layer based on an ultrapure, high-density (>1000 CNTs/μm2) CNT thin film, an ion-gel gate dielectric layer, and a poly(3,4-ethylenedioxythiophene) top gate electrode. All the TFT elements are ink-jet printed at room temperature on a polyimide substrate without involving any photolithography patterning or surface pretreatment steps. This CNT-TFT exhibits a high operating frequency of over 5 GHz and an on-off ratio of over 100. Such an all-ink-jet-printed process eliminates the need for lithography, vacuum processing, and metallization procedures and thus provides a promising technology for low-cost, high-throughput fabrication of large-area high-speed flexible electronic circuits on virtually any desired flexible substrate.

Temperature-dependent photoresponsivity and high-temperature (190K) operation of a quantum dot infrared photodetector

In this letter, a longwave infrared (LWIR) InAs–InGaAs quantum dot infrared photodetector with a peak detection wavelength of 9.9μm is reported. A large photoresponsivity of 2.5A∕W and a high peak specific photodetectivity D* of 1.1×108cmHz1∕2∕W were obtained at the operating temperature of 190K. The QDIP showed a strong temperature-dependent photoresponsivity over the temperature range from 78to190K. This effect is shown to be attributable to temperature-dependent electron capture probability.

Optimizing light absorption in quantum dot infrared photodetectors by tuning surface confinement of surface plasmonic waves

In this paper, we measured the transmission of the 2DSHA surface plasmonic structures and its variation with the hole diameters a of the 2DSHA structures. The relationship between the transmission and the hole diameters a is found to be different from the prediction of Bethes diffraction theorem. We also found that the photocurrent of the quantum dot (QD) infrared photodetectors (QDIPs) with different QD active layer thicknesses show different dependence on the hole diameters a of the 2DSHA structures. The photocurrent of the QDIPs with 10 active QD layers (10-QDIPs) saturates and starts to decrease as the hole diameter a is larger than 1.6 µm, whereas that of the QDIPs with 20 active QD layers (20-QDIPs) increases linearly with the hole diameter. The difference in the hole-diameter dependence of the 10-QDIPs and the 20-QDIPs is attributed to the variation of the near-field spreading in the vertical (surface-normal) direction due to the change in the hole diameters. An over 6 time (6×) photocurrent enhancement is obtained by optimizing the hole diameter of the 2DSHA surface plasmonic structure.

A Fano-type interference enhanced quantum dot infrared photodetector

In this letter, we report a quantum dot photodetector enhanced by Fano-type interference in a metallic two-dimensional (2D) subwavelength hole array (2DSHA). The photocurrent enhancement wavelength shows an offset from the plasmonic resonant peak and corresponds to a dip in the transmission spectrum of the 2DSHA structure. The offset is attributed to the Fano-type interference in the 2DSHA structure. The asymmetric line shapes of the plasmonic resonance are analyzed and agree well with the two-peak Fano-type interference model. Over 100% enhancement in photodetectivity and photoresponsivity is achieved at the wavelength of the Fano dip of the first order plasmonic mode.

Surface plasmonic resonance induced near-field vectors and their contribution to quantum dot infrared photodetector enhancement

In this paper, we analyse surface plasmonic resonance (SPR) induced near-field electric-field vector distribution in the quantum dot (QD) region and determine their roles in quantum dot infrared photodetector (QDIP) enhancement. SPR can be excited in metallic two-dimensional subwavelength hole arrays (2DSHAs) when illuminated at resonant wavelengths. The SPR induced near-field vectors (Ez, Ex and Ey) and their distributions and overlaps with the QD active region are simulated. A long-wave infrared (LWIR) QDIP is fabricated with the 2DSHA plasmonic structure to experimentally measure the SPR enhancement spectrum and compare it with the near-field vector components and their distribution in QDs. We found that QDIP enhancement is closely related to the near-field intensity overlap integral in the QD region. The large near-field overlap integral corresponds to high QDIP enhancement. Such near-field overlap integral dependent plasmonic enhancement is attributed to the interaction of and the electric-dipole interaction in QDs.

Surface plasmonic enhanced polarimetric longwave infrared photodetection with band pass spectral filtering

In this paper, we report a surface plasmonic enhanced polarimetric longwave infrared (LWIR) photodetector. Polarization-selective detection of LWIR incidence with different polarizations is achieved at different plasmonic resonant modes. Band-pass spectral filtering is also provided at the plasmonic resonant modes by the plasmonic enhancement. The extinction ratio (ER) of the polarimetric detection and its limiting factor is discussed.

A modulation-doped longwave infrared quantum dot photodetector with high photoresponsivity

An InAs–InGaAs quantum dot (QD) longwave infrared (LWIR) photodetector (QDIP) with a peak wavelength of 8.2 µm is presented. The QDIP has modulation-doped QD active layers. At 77 K, the QDIP showed high photoresponsivities of 5.4 A W−1 and 3.6 A W−1 at biases of −0.8 V and 0.6 V, respectively. A peak photodetectivity of 7.8 × 109 cm Hz1/2 W−1 was obtained at 77 K in an IR detector compatible package.

Analysis of near-field components of a plasmonic optical antenna and their contribution to quantum dot infrared photodetector enhancement

In this paper, we analyze near-field vector components of a metallic circular disk array (MCDA) plasmonic optical antenna and their contribution to quantum dot infrared photodetector (QDIP) enhancement. The near-field vector components of the MCDA optical antenna and their distribution in the QD active region are simulated. The near-field overlap integral with the QD active region is calculated at different wavelengths and compared with the QDIP enhancement spectrum. The x-component (E(x)) of the near-field vector shows a larger intensity overlap integral and stronger correlation with the QDIP enhancement than E(z) and thus is determined to be the major near-field component to the QDIP enhancement.

Voltage-tunable dual-band InAs quantum-dot infrared photodetectors based on InAs quantum dots with different capping layers

A voltage-tunable, dual-band, InAs quantum-dot infrared photodetector (QDIP) is reported. The QDIP consists of InAs quantum dot layers with GaAs and In0.20Ga0.80As capping layers for extended middle infrared (EMIR, 6–8 µm) and long-wave infrared (LWIR, 8–12 µm) detection, respectively. Voltage-tunable single- and dual-band operations were obtained with good photoresponsivity and photodetectivity selectivity. Since the detection band of the QD FPA can be individually tuned by engineering the capping layers of the InAs QDs, this design approach offers great flexibility in detection for a given spectral region.

A Longwave Infrared Focal Plane Array Enhanced by Backside-Configured Plasmonic Structures

We demonstrate a 320 × 256 longwave infrared focal plane array (FPA) enhanced by backside-configured surface plasmonic structures. The backside-configured plasmonic structures were fabricated on the photodetector side rather than the substrate side. The backside plasmonic FPA shows an average noise-equivalent temperature difference (NEΔT) of 110 mK with a standard deviation σ of 11.09 mK at the blackbody temperature of 30°C. Over 50% improvement in NEΔT is obtained by the backside plasmonic structures. Since the backside configured plasmonic structures can be fabricated on the photodetector side before the substrate lapping and removing, the difficulty of fabricating a plasmonic FPA is greatly reduced.