Papers by Keyword: Dark Current

Abstract: CMOS image sensors can suffer from background noise in absence of any light. In order to suppress this it is important to keep this noise, referred to as dark-current low. This implies that the internal generation current should be very low. Trace metal impurities have been reported to increase the generation current. In this study the trap-assisted generation current contributions due to 7 different metal impurities have been calculated. It was concluded that Cu and Mn impurities yield the highest generation current contribution.

Abstract: This paper presents the structure and the operational principle of CMOS image sensors. And then the reason is illuminated for producing dark current and black level of CMOS image sensors. It is necessary to calibrate dark current and black level to improve quality of CMOS image sensors. The dark current is corrected by optimizing pixel structure, perfecting technology, improving 6layout, and correction double sample. But these ways do not calibrate black level. So, it is important to calibrate black level using black level calibration algorithm in the stage of image processing.

Abstract: Quantum dot infrared photodetectors (QDIPs) have already attracted more and more attention in recent years due to its superior performance. In this paper, a model for the dark current of the QDIP is built. This model supposes that the dark current in the potential barriers is equal to the dark current of the total device according to the structure of the QDIP, and the total electrons transport, the drift velocity and the mobility dependences on the electric field are also taken into account. The corresponding results show the correctness and the validity of the dark current model.

Abstract: CCD dark current is an important index of CCD properties effect, which emerges temperature drift phenomenon with the increasing temperatures. Because of the increasing temperature, CCD noise will increase exponentially. A temperature control device is designed based on DSP and fuzzy PID theory, which is composed of core control chip DSP320F28335, temperature control chip Thermal Electronic Cooler and temperature collecting chip DS18B20. Experiments show that the system can collect temperature timely and adjust temperature effectively. At the same time the system reach predetermined temperature in 2 minutes and error range is about 0.1°C.

Abstract: Cadmium zinc telluride (CZT) material is one of the preferred materials for the fabrication of X-ray and gamma-ray detector. In this paper, it is presented an experimental detector system based on pixellated CZT semiconductor detector. At the same time, some research and design on the surface signal-readout method and the preamplifier circuitry is made. The signal coming from the CdZnTe material exposed to the radiation through the experiment is successfully required. The collection-efficiency between the electron and the hole in the anode is test when the different bias is applied in the pixellated CZT semiconductor detector. The parameter of the CZT detector and validate the responsive effect for the radiation is evaluated.The experiments and evaluation basis for the development of subsequent gamma spectrometer.

Abstract: This paper deals with optical and electrical simulations of 4H-SiC UV-Photodetectors based on pn junctions. The simulations are performed under the UV light, with wavelengths varying between 200 nm and 300 nm. Under reverse bias, the simulation results point out the influence of surface patterns on the current density. The studied structures of the patterns consist in a semicircle with or without a flat surface. The patterned surfaces are parametrized according to the semicircle radius R and the flat surface length L. We show that the optical absorption strongly depends on these parameters, giving a maximum value whatever the wavelength with R = 100 nm and L = 0 nm (no flat surface). However, to optimise the carrier harvest, it is important for the space charge region to be situated in a zone where the optical generation is high. This study shows that the photodetector current density increases within three orders of magnitude (from 9x10^-14 A.cm^-2 to 3x10^-10 A.cm^-2), by using the specific surface pattern given above.

Abstract: We present the simulation results of the InGaAs/InP avalanche photodiode (APD). In the structure a 70 nm InGaAsP grade charge layer and a 70 nm InP charge layer between absorption and multiplication layer have been used for reducing the dark current and achieving higher avalanche gain. A 50 avalanche gain around 35 V breakdown voltages has obtained, which has enhanced by nearly 4 times than that of the conventional InGaAs/InP APD. It has been also shown that the dark current in the device can be significantly reduced nearly one order compared to the corresponding conventional one. The numerical simulation means may design the high gain and low breakdown voltage InGaAs/InP APD.

Abstract: Organic photodiodes operating in the near-infrared (NIR) region with an operating wavelength of about 850 nm, which corresponds to GaAs-based optical devices, were fabricated by wet process. In the active layer, Copper(II)5,9,14,18,23,27,32,36-octabutoxy-2,3-naphthalocyanine was used as NIR absorption material. A wide-bandgap polymer was doped to decrease the dark current, and an n-type organic semiconductor was doped to increase optical sensitivity. To decrease the dark current further, an electron-blocking layer was added onto the anode. This bi-layer structure was found to be very useful for decreasing the dark current. We also evaluated the on/off ratio, which is very important for application to optical communication devices.

Abstract: This paper presents a study of 4H-SiC UV photodetectors based on p+n thin junctions. Two kinds of p+ layers have been implemented, aiming at studying the influence of the junction elaborated by the ion implantation process (and the subsequent annealing) on the device characteristics. Aluminum and Boron dopants have been introduced by beam line and by plasma ion implantation, respectively. Dark currents are lower with Al-implanted diodes (2 pA/cm2 @ - 5 V). Accordingly to simulation results concerning the influence of the junction thickness and doping, plasma B-implanted diodes give rise to the best sensitivity values (1.5x10-1 A/W @ 330 nm).