The ability to integrate electronics with Nanocrystals (NCs) allows utilizing their unique properties for a future optoelectronic device. Combing top down approach using self-assembled hybrid organic-NCs systems, with bottom up components can revolutionize devices in future. In my talk I will present an ultra-high light sensing device based on InAs NCs acting as an optical gate to high electron mobility transistor (HEMT) device. Using a very narrow channel the device quantum efficiency is high as 106V/W, while the single to noise ratio (SNR) enables high sensitivity photon detection. In addition a side gate detector will be present showing enhancement in the sensitivity for light and gas detection. The same concept can be used to develop tunable, simple and flexible detector for the IR range printing semiconducting/conducting carbon nanotubes layer mixed with doped semiconductor nanocrystals.
InAsSb is a promising material for high operating temperature MWIR detectors. InAsSb p-n junction detectors dark
current is g-r limited in the lower temperature range and diffusion limited in the higher ones. In this work we have
investigated the properties GaSb / InAs0.91Sb0.09 heterostructure and its performance as a sensitive MWIR photodetector.
The heterostructure was obtained by MOCVD growth of lattice matched, unintentionally doped layer of InAsSb on NGaSb
substrate. This rectifying N-n heterostructure has the unique type II broken gap interface. I-V and spectral response
were measured at various temperatures in the range 20-300 K. The BLIP temperature was found to be 180 K. R0A
product of 2.5 and 180 Ω•cm2 were measured at 300 and 180 K, respectively. Dual color detection was demonstrated.
The range of spectral response, due to light absorption in GaSb or in InAsSb can be determined by the applied bias. An
optical gain larger than one was observed at temperatures below 120 K. High detectivity values of 1.3•1010 and 4.9•109cm•Hz1/2W-1 at 180 and 300 K respectively were measured.
Gaussian generation-recombination is accepted to be a dominant mechanism of current
noise source in quantum well systems biased by electric field normal to the layers. Recent
experiments in n-type and p-type multiple quantum wells have revealed an additional
pronouncedly non-Gaussian excess current noise with a low cut-off frequency in the kHz
range. The non-Gaussian noise has been attributed to metastable spatial configurations of
electric field. The metastability is originating from negative differential conductance
caused by intervalley scattering in n-type wells and heavy and light holes tunneling in p-type
wells. At a constant bias the system randomly switches between high resistivity state
with low current flow and low resistive state with high current. The non-Gaussianity of
the noise is more pronounced in p-type wells where the time traces of current fluctuations
resemble closely two-level random telegraph signal. In n-type wells the telegraph-like
fluctuations have not been straightforwardly observed. The non-Gaussianity of the noise
in n-type systems has been revealed by nonzero skewness. The differences between noise
properties of between n- and p-type systems have been attributed to small capture
probability of electrons in n-type wells, as opposed to very high capture probability of
holes in p-type wells. As a consequence the noise of any p-type multi-well system is
dominated by the tunneling from the wells while in the n-type the noise appears as a
superposition of many fluctuators associated with individual wells.
InSb has been intensively studied in decades and widely used for fabricating high-performance devices because of its good chemical stability, low effective mass, high electron and hole mobility, and narrow band gap. The most important device applications for InSb are in thermal image sensing in the mid-infrared (3-5 μm) spectral range. The industry standard for fabricating InSb-based focal plane arrays for thermal imaging is based on indium bump technology to interconnect the InSb array to a Si-based readout integrated circuit chip. This hybridization is a "one-piece-at-a-time" process and thus time-consuming and costly. An alternative approach is to employ a device that up-converts mid-infrared light to a wavelength below 1 μm, which can then efficiently be detected by Si charged coupled devices. We reported herein such a mid-infrared optical up-converter based on InSb using wafer fusion technology. The up-conversion device consists of an InSb p+nn+ photodiode and a GaAs/AlGaAs LED, which were grown separately and wafer-bonded together. Experimental results demonstrated mid-infrared to 0.84 μm up-conversion operation at 77K. The measured LED external efficiency and photodiode responsivity show that an external up-conversion efficiency of 0.093 W/W was obtained. Effects of electrical gain and photon recycling inside this integrated device are discussed.
The large increase in the flux-flow voltage noise, commonly observed in the vicinity of the peak-effect in superconductors, is ascribed to a novel noise mechanism. The mechanism consists of random injection of the strongly pinned metastable disordered vortex phase through the sample edges and its subsequent random annealing into the weakly pinned ordered phase in the bulk. This results in large critical current fluctuations causing strong vortex velocity fluctuations. The
excess noise due to this dynamic admixture of two vortex phases is found to display pronounced reentrant behavior. In the Corbino geometry the injection of the metastable phase is prevented and, accordingly, the excess noise disappears. The excess flux-flow noise in the peak-effect regime is dominated by vortex velocity fluctuations while the density fluctuations, frequently considered in the conventional flux-flow noise models, are negligibly weak. Strong nongaussian fluctuations are associated with S-shaped current-voltage characteristics. The spectral properties of the noise reflect the form of the frequency characteristics of the dynamically coexisting
vortex phases which is equivalent to the first order filter response. The cutoff frequency in the spectra corresponds to the time-of-flight of vortices through the disordered part of the sample.
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