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- Light memory function in a double pin SiC devicePublication . Vaz da Silva, V; Vieira, Manuela; Vieira, Manuel; Louro, Paula; Barata, ManuelA double pi'npin heterostructure based on amorphous SiC has a non linear spectral gain which is a function of the signal wavelength that impinges on its front or back surface. An impulse of a configurable length and amplitude is applied to a 390 nm LED which illuminates one of the sensor surfaces, followed by a time period without any illumination after which an input signal with a different wavelength is impinged upon the front surface. Results show that the intensity and duration of the impulse illumination of the surfaces influences the sensor's response with different output for the same input signal. This paper studies this effect and proposes an application as a short term light memory. (C) 2015 Elsevier B.V. All rights reserved.
- Seven channel wavelength demultiplexer using a tandem a:SiC-H/a:Si-H photo sensorPublication . Silva, Vítor; Barata, Manuel; Vieira, Manuel; Louro, Paula; Vieira, ManuelaThe pi'npin photo device is a tandem a: SiC-H / a: Si-H heterostructures. The device is electrically biased and can also be optically biased by ultra-violet illumination of the front or back surfaces. The front surface is also used for several pulsed single wavelength signals within the visible range. Experimental results show that the ultra-violet bias illumination at the front surface of the device enhances wavelengths longer than 500 nm while quenching the wavelengths shorter than 500 nm. The opposite happens when the bias is set at the back surface of the device; wavelengths shorter than 500 nm are enhanced while the ones above are quenched. Several digital applications have been built using the p'inpin device. This paper focuses on the use of the pi'npin device for seven channel Wavelength Division Multiplexing (WDM) digital communication using Manchester coded signals, with a single wavelength for each channel. The seven channels form a frame with 7*256 bits with a preamble for signal intensity and synchronization purposes. Results show that the clustering of the received signal enables the successful recovery of the seven channel data using the front and back illumination of the surfaces of the pi'npin photo device.
- Five channel WDM communication using a single a:SiC-H double pin photo devicePublication . Vaz da Silva, V; Barata, Manuel; Louro, Paula; Vieira, Manuel; Vieira, ManuelaAmorphous SiC heterostructures built as a double pin device has a non linear spectral gain which is a function of the signal wavelength that impinges on its front or back surface. Illuminating the device with several single wavelength data channels in the visible spectrum allows for Wavelength Division Multiplexing (WDM) digital communication. Using fixed ultra-violet illumination at the front or back surfaces enables the recovery of the multiplexed channels. Five channels, each using a single wavelength which is modulated by a Manchester coded signal at 12,000 bps, form a frame with 1024 bits with a preamble for signal intensity and synchronisation purposes. Results show that the clustering of the received signal enables the successful recovery of the five channel data using the front and back illumination of the surfaces of the double pin photo device. (C) 2015 Elsevier B.V. All rights reserved.
- Majority logical function using a pi'npin a-SiC:H structurePublication . Silva, V.; Barata, Manuel; Louro, Paula; Vieira, Manuel; Vieira, ManuelaThe majority logic function has a true output value whenever more than half of the inputs have a true value. Majority logic, also known as majority voting, is used in many systems, for fault-tolerant design, in bioelectronics, and quantum dot cellular automata. The pi'npin heterostructure p-i'(a-SiC:H)-n/p-i(a-Si:H)-n can be illuminated from both back and front surfaces. Steady state illumination, optical bias, controls the light-to-dark sensitivity in the visible range. Several input data channels, each with a different wavelength, illuminate the front surface. Results show that a majority function of 3 and 5 inputs (MAJ-3, MAJ-5) is built with the pi'npin device projecting the way for a MAJ-n function.
- Logical functions in a tandem SiC devicePublication . Vaz da Silva, V; Vieira, Manuel; Louro, Paula; Barata, Manuel; Vieira, ManuelaThis study demonstrates logical functions based on SiC technology. The device consists of a p-i’(a-SiC:H)-n/p-i(a-Si:H)-n heterostructure with low conductivity doped layers. Experimental optoelectronic characterization of the fabricated device is presented and shows the feasibility of tailoring channel bandwidth and wavelength by optical bias through illumination in the back and front sides with violet light. Two digital light signals are applied to the front side of the device while violet light steadily shines either at the back or front sides. Each digital light signal is composed by two wavelengths, one from the long and the other from the short visible wavelength range. One digital signal is the Red–Blue pair and the other the Green–Violet. The NOT logical function is shown with the Red–Blue pair likewise with the Green–Violet pair. The background biasing either at front or at the back side allows for an inverted signal or non inverted signal. Experimental results show and explain the interaction of two digital signal pairs and the identification of the logical AND, OR and XOR operations by the selection of the violet biasing illumination side.