scholarly journals BULK PHOTOEFFECTS IN INHOMOGENEOUS SEMICONDUCTORS

1960 ◽  
Vol 38 (10) ◽  
pp. 1328-1342 ◽  
Author(s):  
C. D. Cox
Keyword(s):  
Density Gradient ◽  
Close Agreement ◽  
Theoretical Expression ◽  
Light Illumination ◽  
Theoretical Relation ◽  
Impurity Density ◽  
Photoelectromotive Force ◽  
Weak Light ◽  
Resistance Decrease

A photoelectromotive force is observed when a semiconductor is illuminated in the region of a bulk inhomogeneity. A theoretical expression for the bulk photo-e.m.f. is derived which is valid for all levels of illumination in the region of an arbitrary impurity density gradient. With appropriate approximations the complete expression is simplified for the cases of weak and saturation illumination in inhomogeneous extrinsic and nearly intrinsic semiconductors, and in p–n and l–h junctions. The theoretical relation between bulk photo-e.m.f. and photoconductive resistance decrease is examined.Bulk photo-e.m.f. measurements were made on inhomogeneous germanium filaments. These showed the photo-e.m.f. to be linear with weak light illumination. Strong illumination photo-e.m.f. was shown to depend on the impurity distributions adjacent to the illuminated regions. The ratio of bulk photo-e.m.f. to photoconductive resistance decrease was constant at weak illumination in agreement with the theory. Measurements of the photo-e.m.f. as a function of temperature showed a close agreement with the predicted behavior in the near intrinsic range of conductivity.

Ultrasensitive broadband photodetectors based on two-dimensional Bi2O2Te films

2021 ◽  
Author(s):  
Pin Tian ◽  
Hongbo Wu ◽  
Libin Tang ◽  
Jinzhong Xiang ◽  
Rongbin Ji ◽  
...  
Keyword(s):  
Large Scale ◽  
2D Materials ◽  
Complementary Metal Oxide Semiconductor ◽  
Cmos Technology ◽  
Photocurrent Density ◽  
Short Wave ◽  
Oxide Semiconductor ◽  
Light Illumination ◽  
Two Dimensional ◽  
Weak Light

Abstract Two-dimensional (2D) materials exhibit many unique optical and electronic properties that are highly desirable for application in optoelectronics. Here, we report the study of photodetector based on 2D Bi2O2Te grown on n-Si substrate. The 2D Bi2O2Te material was transformed from sputtered Bi2Te3 ultrathin film after rapid annealing at 400 ℃ for 10 min in air atmosphere. The photodetector was capable of detecting a broad wavelength from 210 nm to 2.4 μm with excellent responsivity of up to 3x105 and 2x104 AW-1, and detectivity of 4x1015 and 2x1014 Jones at deep ultraviolet (UV) and short-wave infrared (SWIR) under weak light illumination, respectively. The effectiveness of 2D materials in weak light detection was investigated by analysis of the photocurrent density contribution. Importantly, the facile growth process with low annealing temperature would allow direct large-scale integration of the 2D Bi2O2Te materials with complementary metal-oxide–semiconductor (CMOS) technology.

scholarly journals High responsivity in MoS2 phototransistors based on charge trapping HfO2 dielectrics

2020 ◽  
Vol 1 (1) ◽  
Author(s):  
Roda Nur ◽  
Takashi Tsuchiya ◽  
Kasidit Toprasertpong ◽  
Kazuya Terabe ◽  
Shinichi Takagi ◽  
...  
Keyword(s):  
Transition Metal Dichalcogenides ◽  
Charge Trapping ◽  
Dual Function ◽  
Light Illumination ◽  
Low Light ◽  
High Responsivity ◽  
Metal Dichalcogenides ◽  
High Resolution Images ◽  
Weak Light ◽  
Light Signals

Abstract2D Transition Metal Dichalcogenides hold a promising potential in future optoelectronic applications due to their high photoresponsivity and tunable band structure for broadband photodetection. In imaging applications, the detection of weak light signals is crucial for creating a better contrast between bright and dark pixels in order to achieve high resolution images. The photogating effect has been previously shown to offer high light sensitivities; however, the key features required to create this as a dominating photoresponse has yet to be discussed. Here, we report high responsivity and high photogain MoS2 phototransistors based on the dual function of HfO2 as a dielectric and charge trapping layer to enhance the photogating effect. As a result, these devices offered a very large responsivity of 1.1 × 106 A W−1, a photogain >109, and a detectivity of 5.6 × 1013 Jones under low light illumination. This work offers a CMOS compatible process and technique to develop highly photosensitive phototransistors for future low-powered imaging applications.

Synthesis of Er3+/Zn2+ co-doped Bi2WO6 with highly efficient photocatalytic performance under natural indoor weak light illumination

2017 ◽  
Vol 43 (2) ◽  
pp. 2598-2605 ◽  
Author(s):  
Yuanyuan Zhang ◽  
Yongchao Ma ◽  
Qingzhi Liu ◽  
Haiyan Jiang ◽  
Qi Wang ◽  
...  
Keyword(s):  
Photocatalytic Performance ◽  
Light Illumination ◽  
Highly Efficient ◽  
Weak Light ◽  
Co Doped

Photoconductivity of InN grown by MOVPE: Low temperature and weak light illumination

2017 ◽  
Vol 110 (4) ◽  
pp. 042104 ◽  
Author(s):  
Ting-Ting Kang ◽  
Yuhui Zhang ◽  
Ping-Ping Chen ◽  
ZhiHai Wang ◽  
Akio Yamamoto
Keyword(s):  
Low Temperature ◽  
Light Illumination ◽  
Weak Light

scholarly journals Geostrophic Closure of the Zonally Averaged Atlantic Meridional Overturning Circulation

2016 ◽  
Vol 46 (3) ◽  
pp. 895-917 ◽  
Author(s):  
Florian Sévellec ◽  
Thierry Huck
Keyword(s):  
Pressure Gradient ◽  
Density Gradient ◽  
Atlantic Meridional Overturning Circulation ◽  
Meridional Overturning Circulation ◽  
Theoretical Expression ◽  
Length Scale ◽  
Overturning Circulation ◽  
The North ◽  
Meridional Overturning ◽  
Meridional Density Gradient

AbstractIt is typically assumed that the meridional density gradient in the North Atlantic is well and positively correlated with the Atlantic meridional overturning circulation (AMOC). In numerical “water-hosing” experiments, for example, imposing an anomalous freshwater flux in the Northern Hemisphere leads to a slowdown of the AMOC. However, on planetary scale, the first-order dynamics are linked to the geostrophic balance, relating the north–south pressure gradient to the zonal circulation. In this study, these two approaches are reconciled. At steady state and under geostrophic dynamics, an analytical expression is derived to relate the zonal and meridional pressure gradient. This solution is only valid where the meridional density gradient length scale is shorter than Earth’s curvature length scale, that is, north of 35°N. This theoretical expression links the north–south density gradient to the AMOC and can be used as a closure for zonally averaged ocean models. Assumptions and shortcomings of the approach are presented. Implications of these results for paleoclimate problems such as AMOC collapse and asymmetry in the meridional overturning circulation of the Atlantic and of the Pacific are discussed.

Fabrication and Photoelectrical Properties of AZO/SiO2/p-Si Based Device

2008 ◽  
Vol 1123 ◽  
Author(s):  
Z.Q. Ma ◽  
B. He ◽  
J. Xu ◽  
L. Zhao ◽  
F. Li ◽  
...  
Keyword(s):  
Minority Carrier ◽  
Zno Films ◽  
Light Illumination ◽  
Radio Frequency Magnetron Sputtering ◽  
Voltage Measurement ◽  
Photoelectrical Properties ◽  
Tunneling Diode ◽  
Current Voltage ◽  
Heterojunction Device ◽  
Weak Light

AbstractIn order to fabricate AZO/SiO2/p-Si heterojunction device and let it be an absorber of ultraviolet response cell. Zinc oxide (ZnO) thin films doped with aluminum (AZO) were deposited on p-Si(100) substrates covered with silicon dioxide (SiO2) by radio frequency magnetron sputtering. The optical and electrical properties of the Al doped - ZnO films were characterized by UV-VIS spectrophotometer, current-voltage measurement, and four point probe technique, respectively. The results show that the device is a typical tunneling diode for minority carrier and a strong obstructing effect from majority carriers. The potential rectifying behavior and photovoltaic characteristic is present at dark current and weak light illumination, respectively.

Impurity density gradient influence on trapped particle modes

2018 ◽  
Vol 25 (6) ◽  
pp. 062307 ◽  
Author(s):  
M. Idouakass ◽  
E. Gravier ◽  
M. Lesur ◽  
J. Médina ◽  
T. Réveillé ◽  
...  
Keyword(s):  
Density Gradient ◽  
Impurity Density

scholarly journals Gate Dependent Tunable Photosensitivity of Copper Phthalocyanine Based Organic Field Effect Transistors

2019 ◽  
Vol 8 (10) ◽  
pp. 4687-4694
Keyword(s):  
Field Effect ◽  
Copper Phthalocyanine ◽  
Field Effect Transistors ◽  
Monochromatic Light ◽  
Visible Region ◽  
High Sensitivity ◽  
Low Noise ◽  
Electromagnetic Spectrum ◽  
Light Illumination ◽  
Weak Light

Organic field effect transistor (OFET) based photodetector with high sensitivity was fabricated using copper phthalocyanine (CuPc) as photoactive channel for weak light detection. The device fabrication was conducted at room temperature using thermal evaporation technique. The opto-electrical properties of the devices under dark and light conditions are studied in this work. The performance of the photodetector depends on the incident wavelength and the intensity of the incident monochromatic light. We also show that the photoresponse could be tuned by the gate bias, which offers an additional benefit for practical applications. The transfer characteristics of the devices appear to enhance under light illumination. A slight enhancement in the carrier mobility was also detected upon illumination. Similarly, the subthreshold swing has been reduced from 1.31 ± 0.18 V/decade under dark condition to 0.76 ± 0.12 V/decade under illumination. Further impact of gate voltage on responsivity, on/off ratio and detectivity was also studied for the proposed device. The maximum photosensitivity and responsivity obtained from these OFET based photodetectors was 237.21 ± 8.02 and 7.77 ± 0.17 A/W respectively at a power density of 1 mW/cm2 while operating at an input voltage of 4 V and bias voltage of -5 V. Also, a maximum detectivity of 1.38 ± 0.03×10 12 Jones was obtained under the same operating condition. The high sensitivity, good stability, low noise and fast response towards weak light with different wavelength imply that OFET based photodetectors are particularly suitable for photodetection in the visible region of electromagnetic spectrum.

Activated Prominences; Mechanisms for Activation and Eruption

1979 ◽  
Vol 44 ◽  
pp. 307-313
Author(s):  
D.S. Spicer
Keyword(s):  
Pressure Gradient ◽  
Density Gradient ◽  
Current Density ◽  
Convective Instability ◽  
Tearing Mode ◽  
Magnetic Shear ◽  
Long Wavelength ◽  
Ideal Mhd ◽  
Gradient Change ◽  
Accelerated Particles

A possible relationship between the hot prominence transition sheath, increased internal turbulent and/or helical motion prior to prominence eruption and the prominence eruption (“disparition brusque”) is discussed. The associated darkening of the filament or brightening of the prominence is interpreted as a change in the prominence’s internal pressure gradient which, if of the correct sign, can lead to short wavelength turbulent convection within the prominence. Associated with such a pressure gradient change may be the alteration of the current density gradient within the prominence. Such a change in the current density gradient may also be due to the relative motion of the neighbouring plages thereby increasing the magnetic shear within the prominence, i.e., steepening the current density gradient. Depending on the magnitude of the current density gradient, i.e., magnetic shear, disruption of the prominence can occur by either a long wavelength ideal MHD helical (“kink”) convective instability and/or a long wavelength resistive helical (“kink”) convective instability (tearing mode). The long wavelength ideal MHD helical instability will lead to helical rotation and thus unwinding due to diamagnetic effects and plasma ejections due to convection. The long wavelength resistive helical instability will lead to both unwinding and plasma ejections, but also to accelerated plasma flow, long wavelength magnetic field filamentation, accelerated particles and long wavelength heating internal to the prominence.

Uranyl Acetate and Rotary Shadowing to Increase the Contrast of Small Aggregated Virus Particles

1969 ◽  
Vol 27 ◽  
pp. 424-425
Author(s):  
Lee F. Ellis ◽  
Richard M. Van Frank ◽  
Walter J. Kleinschmidt
Keyword(s):  
Electron Microscopy ◽  
Tissue Culture ◽  
Density Gradient ◽  
Density Gradient Centrifugation ◽  
Gradient Centrifugation ◽  
Uranyl Acetate ◽  
Interferon Inducer ◽  
Virus Particles ◽  
Staining Methods ◽  
Rotary Shadowing

The extract from Penicillum stoliniferum, known as statolon, has been purified by density gradient centrifugation. These centrifuge fractions contained virus particles that are an interferon inducer in mice or in tissue culture. Highly purified preparations of these particles are difficult to enumerate by electron microscopy because of aggregation. Therefore a study of staining methods was undertaken.

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