Matrix Factorization Techniques for Recommender Systems

In this review article a comprehensive analysis of the developments in ultraviolet (UV) detector technology is described. At the beginning, the classification of UV detectors and general requirements imposed on these detectors are presented. Further considerations are restricted to modern semiconductor UV detectors, so the basic theory of photoconductive and photovoltaic detectors is presented in a uniform way convenient for various detector materials. Next, the current state of the art of different types of semiconductor UV detectors is presented. Hitherto, the semiconductor UV detectors have been mainly fabricated using Si. Industries such as the aerospace, automotive, petroleum, and others have continuously provided the impetus pushing the development of fringe technologies which are tolerant of increasingly high temperatures and hostile environments. As a result, the main efforts are currently directed to a new generation of UV detectors fabricated from wide band‐gap semiconductors the most promising ...

Semiconductor ultraviolet detectors

Industries such as the automotive, aerospace or military, as well as environmental and biological research have promoted the development of ultraviolet (UV) photodetectors capable of operating at high temperatures and in hostile environments. UV-enhanced Si photodiodes are hence giving way to a new generation of UV detectors fabricated from wide-bandgap semiconductors, such as SiC, diamond, III-nitrides, ZnS, ZnO, or ZnSe. This paper provides a general review of latest progresses in wide-bandgap semiconductor photodetectors.

https://iopscience.iop.org/article/10.1088/0268-1242/18/4/201/pdf

Wide-bandgap semiconductor ultraviolet photodetectors

Ultraviolet (UV) photodetectors have drawn extensive attention owing to their applications in industrial, environmental and even biological fields. Compared to UV-enhanced Si photodetectors, a new generation of wide bandgap semiconductors, such as (Al, In) GaN, diamond, and SiC, have the advantages of high responsivity, high thermal stability, robust radiation hardness and high response speed. On the other hand, one-dimensional (1D) nanostructure semiconductors with a wide bandgap, such as β-Ga2O3, GaN, ZnO, or other metal-oxide nanostructures, also show their potential for high-efficiency UV photodetection. In some cases such as flame detection, high-temperature thermally stable detectors with high performance are required. This article provides a comprehensive review on the state-of-the-art research activities in the UV photodetection field, including not only semiconductor thin films, but also 1D nanostructured materials, which are attracting more and more attention in the detection field. A special focus is given on the thermal stability of the developed devices, which is one of the key characteristics for the real applications.

A Comprehensive Review of Semiconductor Ultraviolet Photodetectors: From Thin Film to One-Dimensional Nanostructures

Au contacts. The B-FTS approach exhibits the unique feature of ultra-rapid growth of ZnO nanotetrapods within few milliseconds and simultaneously in situ bridging electrical contacts. These bridging nanotetrapods were directly integrated on a chip and demonstrated signifi cantly improved performances as a UV photodetector. Comparison of the UV photodetectors performances built from interpenetrating ZnO nano-microstructures fabricated by B-FTS and C-FTS techniques are presented. Fastest response/recovery time constant (≈32 ms) under 365 nm UV light irradiation of B-FTS-made photodetectors (on/off ratio ≈4.5 ◊ 10 3 at 2.4 V) is reported. Different type of nanojunctions formed between neighbor nanowires or nanotetrapods (with ‘arm’ thickness <50 nm) could be the reason for such improved characteristics. The role of nanojunctions in fast UV photodetectors from networked ZnO nanowires and nanotetrapods is discussed. On the basis of the rapid B-FTS fabrication process and fast UV photodetection capabilities, such networked ZnO nanotetrapods can be potential candidates for various nanosensor applications.

Rapid fabrication technique for interpenetrated ZnO nanotetrapod networks for fast UV sensors.

Thin film diamond has been used to fabricate a photodetector which displays high sensitivity to deep UV light, with an external quantum efficiency of greater than one, a dark current of less than 0.1nA and which is near ‘blind’ to visible light.

A High Performance UV Photodetector from Thin Film Diamond

The effects of doping InAs quantum dots (QDs) with Si on charge carrier dynamics and recombination in
the InAs/GaAs quantum dot solar cells with AlAs cap layers was investigated. Non-radiative and
radiative recombination paths in the doped cells were identified by changes in emission intensity, longwavelength photovoltage (PV) as well as time-resolved PV and photoluminescence (PL) measurements.
We find that the reduction of long-wavelength PV and PL with n-doping is due to the electron population
of the QD ground states and shrinkage of the depletion layer. The time constants, derived from the timeresolved PV, grow non-monotonically with increasing of the doping density in the QDs due to
redistribution of electrostatic potential in the intrinsic region of p-i-n diode and electron population of
EL2 defect states of GaAs barriers. We also find that the ground state emission from the InAs QDs
decreases with n-doping. The results show that PL traces depends on carrier dynamic in the top QD layers
populated partially with electrons from ionized impurities, whereas PV transients were found to be
strongly dependent on recombination via QD and defect states located outside the depletion layer. We
conclude that the non-radiative recombination of photogenerated electrons and holes via defects is
suppressed due to the spatial separation by the local electric fields in and around doped AlAs/InAs QDs,
as the potential profile of the intrinsic region is modulated spatially by built-in charges. The interpretation
of experimental data suggests limiting mechanisms in the InAs/GaAs quantum dot solar cells operation
and sheds light on possible approaches for their further improvement.

/pdf/carrier-dynamics-and-recombination-in-silicon-doped-inas-484vpo2l52.pdf

Carrier dynamics and recombination in silicon doped InAs/GaAs quantum dot solar cells with AlAs cap layers

Techniques and architectures for data modeling and management. Data modeling services are provided to agents within multiple different operating environments of a computing environment having at least one database stored on one or more physical memory devices communicatively coupled with one or more hardware processors the one or physical memory devices. Building and versioning of data modeling projects is coordinated and data utilized for the data modeling projects with the one or more hardware processors.

Techniques and architectures for managing disparate heterogeneous cloud-based resources

bstract A high temperature depletion-mode metal-insulator field effect transistor (MISFET) has been fabricated from thin film polycrystalline diamond with a p-type (boron doped) channel and an insulating diamond gate. This device was successfully operated at 300 °C with low gate leakage currents, displaying pinch-off when in depletion and high levels of channel current modulation in enhancement. A transconductance value of 174 μS mm −1 has been measured, the highest reported value to date for this type of device.

Thin film diamond metal-insulator field effect transistor for high temperature applications

In this paper, we investigate a resource allocation problem in recommendation systems where unknown new items keep coming to the system at different time. The task is to recommend (allocate) each user a limited number of new items. The objective is to maximize the overall positive response rate. This problem is non-trivial because, on one hand, we need to allocate these news items to users who are helpful for learning new item feature profiles using the limited recommendation opportunities (resources) in order to improve prediction accuracy; on the other hand, allocate these items to users who would most likely purchase them on the basis of the new item information gathered so far in order to maximize positive response rate. In this paper, we propose a two-stage batch solution to approximately optimize the objective, using group buying as a working example. During the first stage, we estimate the user purchase decisions towards new items by allocating some resources for exploration. During the second stage, we optimally allocate the remaining resources for exploitation according to the prediction and the operational constraints using the binary integer programming technique. Our experiments indicate that the proposed approach significantly improves the positive response rate.

Simon S.M. Chan

Papers

A High Performance UV Photodetector from Thin Film Diamond

Carrier dynamics and recombination in silicon doped InAs/GaAs quantum dot solar cells with AlAs cap layers

Techniques and architectures for managing disparate heterogeneous cloud-based resources

Thin film diamond metal-insulator field effect transistor for high temperature applications

Constrained by limited information and recommendation opportunities: An exploration and exploitation problem for recommender systems