Our recently published results show a much reduced dark current and enhanced speed from our second-generation electron-Injection detectors, due to the introduction of an isolation method. However, these results have been limited to single-element detectors. A natural next step is to incorporate these new devices into a focal plane array (FPA), since we have already achieved very attractive results from an FPA based on the first-generation devices. Despite the high-performance characteristics of second generation devices, isolation introduces new processing steps and a robust procedure is required for realization of focal plane arrays (FPA) with good uniformity and yield. Here we report our systematic evaluation of the processing steps, and in particular the effect of the processing temperature, on the device dark current and uniformity. Our goal is to produce ultra-low dark current FPA based on isolated electron-injection detectors, and to approach single-photon sensitivity.
KEYWORDS: Antennas, Near field optics, Near field, Electron beam lithography, Nonlinear optics, Reactive ion etching, Switching, Scattering, Plasmonics, Nanoantennas
We have introduce optomechanical nanoantennae, which showed dramatic changes in scattering
properties by minuscule changes in geometry. These structures are very compact, with a volume 500
times smaller than free space optical wavelength volume. Through these optical elements, far-field can
directly control the near-field of antenna by mechanical reconfiguration. Here we present the functionality
of the optomechanical nanoantenna and challenges in fabricating and measuring these devices.
Our group has designed and developed a novel telecom band photon detector called the electron-injection detector. The detector provides a high avalanche-free internal-amplification and a stable excess noise factor of near unity while operating at linear-mode with low bias voltages. In our previous reports on un-isolated detectors, the large dark current of the detectors prevented long integration times in the camera. Furthermore, the bandwidth of the un-isolated detectors was in the KHz range. Recently, by changing the 3D geometry and isolating the detectors from each other, we have achieved 3 orders of magnitude reduction in dark current at same bias voltage and temperature compared to our previous results. Isolated detectors have internal dark current densities of 0.1nA/cm2 at 160 K. Furthermore, they have a bandwidth that is 4 orders of magnitude higher than the un-isolated devices. In this paper we report room temperature and low temperature characteristics of the isolated electron-injection detectors. We show that the measured optical gain displays a small dependence on temperature over our measured range down to 220 K.
KEYWORDS: Quantum well infrared photodetectors, Plasmonics, Signal to noise ratio, Signal processing, Metals, Quantum efficiency, Sensors, Absorption, Photoresist materials, Etching
Quantum Well Infrared Photodetector (QWIP) is an attractive candidate for long-wave infrared detection but is limited due its low quantum efficiency and its polarization sensitivity. Here we propose a detector with an embedded plasmonic structure surrounding the detector that is protected. Our detector uses an array of pillars surrounded by a plasmonic metal and contacted from the top making one “super pixel”. This structure is within close proximity of the active medium and is protected by the top contact. This configuration also eliminates non-absorbing semiconductor eliminating significant dark current.
Nano-fabrication technologies are usually associated with complication, high cost, and limited area of coverage.
However, advances in optics and nanophotonics constantly demand novel fabrications for nano-manufacturing
systems with extraordinary optical, electrical, mechanical, or thermal responses. While, these properties are vital for
health, energy, and information technology applications, proposing new methods of fabricating nanostructures that
can be compatible with high throughput and large scale manufacturing is quite desirable. Here, we propose a deep
ultra-violet (DUV) photolithography technique that can produce a variety of periodic nanostructure clusters with
sub-100 nm feature sizes. The method is based on microsphere nanolithography, which focuses DUV field into a socalled
photonic nano-jet – a propagative intensive field underneath the sphere. The position of a photonic nano-jet
can be moved by changing the angle of exposure. The DUV microsphere nanolithography is inherently self-aligned,
mask-less and optics-less (the bulky optical element such as lens is not required), which makes this method
attractive for low-cost and high-throughput nano-manufacturing schemes, such as roll-to-roll production. Here, we
present fabricated arrays of nanoscale complex structures to demonstrate the capabilities of this nanolithography
method.
Various metallic nano-structured thin films were fabricated by oblique angle deposition. Their optical, electrical and
structural properties were investigated to explore potential applications in optoelectronic field. The shape, size and
density of metal films were discussed based on SEM images and their thermal characteristics. The optical reflectance,
transmittance, and absorptance measurements showed unique optical properties of each metallic nano-structured films.
Indeed, ellipsometry measurement and resistance measurement were performed to investigate directivity of nanocolumnar
films depending on polarization properties, and conductivity, respectively.
Fabrication of nanostructures for applications such as plasmonics and metamaterials are typically accompanied by a slow production and limited area due to the required sub-micron feature sizes. In these applications, periodic array of metal/dielectric features can produce optical resonance responses such as optical field enhancement response, Fano response, chiral response, and negative refractive index. Here, we propose a mask-less photolithography technique that can produce a variety of periodic nanostructure clusters. The method is based on microsphere nanolithography, which focuses UV field into the so-called photonic jet which is a propagative intensive field underneath the sphere. The position of photonic jet can be moved by changing the angle of exposure. The method introduces a controllable scheme to realize nano-gap size by controlling the angle of exposure. The feature sizes generated by this method are about one third of exposure wavelength. The method is compatible with highthroughput nano-manufacturing schemes, such as roll-to-roll production. Here we present some examples to demonstrate the capabilities of this method in producing an array of complex plasmonic molecules over a large area. The periodicity of array and element’s diameter can be tuned by microsphere size and exposure/developing time, respectively. Tilted exposure lithography inherently is self-aligned and readily extendible to deep UV lithography due to absent of mask and optical elements. FDTD simulation agrees well with our experimental results, and suggests that much smaller feature sizes can be achieved at shorter wavelengths.
In order to lessen the strain of cooling requirements on mid-infrared detectors, reducing the volume of the detecting medium is one promising solution. It is necessary to augment the absorption (quantum efficiency) lost when shrinking the detector volume. We present a Quantum Well Infrared Photodetector with a plasmonic structure embedded within and around the detection media. This device has a self-aligned plasmonic-hole array designed for 8μm wavelength and a planar top contact to the array of detector material. This arrangement has an expected field enhancement of an order of magnitude and lends itself to making a Focal Plane Array.
Our group has designed and developed a new SWIR single photon detector called the nano-injection detector that is conceptually designed with biological inspirations taken from the rod cells in human eye. The detector couples a nanoscale sensory region with a large absorption volume to provide avalanche free internal amplification while operating at linear regime with low bias voltages. The low voltage operation makes the detector to be fully compatible with available CMOS technologies. Because there is no photon reemission, detectors can be formed into high-density single-photon detector arrays. As such, the nano injection detectors are viable candidates for SPD and imaging at the short-wave infrared band. Our measurements in 2007 proved a high SNR and a stable excess noise factor of near unity. We are reporting on a high speed version of the detector with 4 orders of magnitude enhancement in speed as well as 2 orders of magnitude reduction in dark current (30nA vs. 10 uA at 1.5V).
The loss in optical antennas can affect their performance for their practical use in many branches of science
such as biological and solar cell applications. However the big question is that how much loss is due to the
joule heating in the metals. This would affect the efficiency of solar cells and is very important for single
photon detection and also for some applications where high heat generation in nanoantennas is desirable, for
example, payload release for cancer treatment. There are few groups who have done temperature
measurements by methods such as Raman spectroscopy or fluorescence polarization anisotropy. The latter
method, which is more reliable than Raman spectroscopy, requires the deposition of fluorescent molecules on
the antenna surface. The molecules and the polarization of radiation rotate depending upon the surface
temperature. The reported temperature measurement accuracy in this method is about 0.1° C. Here we present
a method based on thermo-reflectance that allows better temperature accuracy as well as spatial resolution of
500 nm. Moreover, this method does not require the addition of new materials to the nanoantenna. We present
the measured heat dissipation from bull’s-eye nanoantennas and compare them with 3D simulation results.
This study reports broadband antireflective subwavelength structures (SWS) on various semiconductor materials for
near-infrared detector applications. Two fabrication methods are proposed, i.e., a lenslike shape transfer and an overall
dry etch process of Ag nanoparticles. These methods provide relatively simple, fast, inexpensive process steps, which is
applicable for practical device applications. The fabricated SWS showed extremely lower reflectance spectra compared
to that of flat surface in the near-IR range, indicating good agreement with the simulation results. We also propose
amorphous silicon SWS on InGaAs photodetector to enhance the absorption efficiency.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.