![I-Reverse voltage characteristics of: (a) nickel samples D1, D2 and D3 (b) aluminum samples D4, D5 and D6 for dark and under two different light intensities. The C-V characteristics for nickel and aluminum samples at 10 and 100 kHz frequencies were drawn as shown in figure 6 (a and b).. These characteristics were used to calculate the internal potential barrier height. At 10 kHz three regions were clearly apparent [12]. A recombination region appeared when the forward voltage is above 0.5V. The inversion region is associated with reverse voltage. The depletion region appeared between the two voltages mentioned. The depletion layer width is proportional with the applied voltage according to equations (3 &5). This explains why the capacitance increases linearly with the applied voltage on the depletion region that reduces the width of the region. Nickel and aluminum samples have different behavior,](https://www.researchgate.net/publication/287569295/figure/fig4/AS:563877109616642@1511450187385/Reverse-voltage-characteristics-of-a-nickel-samples-D1-D2-and-D3-b-aluminum-samples_Q320.jpg)
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The Effects of MOS Layers on Sensing Properties of MOS Photosensor
Abstract and Figures
In this research work, many samples of metal -oxide -silicon photosensors were laboratory prepared by thermal evaporation techniques. Some silicon samples were left in the air for a predefined time for SiO2 to grow naturally, while others were thermally coated with measured thickness of SiO. A number of the samples were coated with nickel while others with aluminum and one sample was coated with indium. Various tests and measurements were conducted; these include transmittance tests with a range of wavelength and for different thicknesses. The ideality factors of the samples and the potential barrier height were calculated from I-V and C-V characteristics. The photogenerated current of the samples were also measured at photoconductive mode under reverse voltage. Quantum efficiency measurement indicated that native oxide samples provided higher quantum efficiency than those thermally deposited samples. Detectivity measurement showed that thermally deposited oxide samples had low detectivity as compared to native oxide samples.
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... However, in case of poor junctions, the injection current can be the dominating mechanism for transient leakage current at relatively high biases, the dark current decays initially and then rises to a steady-state value [7]. The mid-gap states energy levels and their spatial distribution in I-layer and at P-I interface can be obtained [8,9] from the transient dark current and steady-state thermal generation current. Emission of carriers from the P-I and N-I interface and thermal generation in I-layer, which is a voltage dependent at low biases, mainly contributes to the dark current. ...
... It is found that the dangling bond states energy levels distributed in range from shallow to deep levels and activated at low bias voltages and visible pulses illumination, are responsible for the characteristic photodiode response shape [8]. The advantages of PIN photodiode and MOS structure have been combined together to produce lateral PIN photosensors with maximum photocurrent and low dark current and achieved high sensitivity and responsivity with low voltage bias [9]. LPIN photodiode fabricated in CMOS processes [10] achieved bandwidth compatible with 10 Gb/sec and even higher data rate [11]. ...
this research aims to study and discuss the theoretical models and simulation of optoelectronic properties of a-Si-H PIN photosensors based on Shockley–Read-Hall assumptions. The variation of carrier life time, recombination and generation rates as a function of the intrinsic layer (I-layer) thickness will be simulated using MATLAB program. The effects of intrinsic layer thickness on electrons and holes concentration, collection efficiency and short circuit current density have been studied and analyzed. It has been found that as the thickness increased, the parameters: recombination rate, generation rate, internal electric field, electrons and holes concentration, carriers’ life times, and short circuit current density, were subjected to some variations.
One of the most promising solar cell devices is cadmium telluride (CdTe) based. These cells however, have their own problems of stability and degradation in efficiency. Measurements show that CdS/CdTe solar cell has high series resis-tance which degrades the performance of solar cell energy conversion. Both active layers (CdS and CdTe) had been fabricated by thermal evaporation and tested individually. It was found that CdS window layer of 300 nm have the low-est series resistance with maximum light absorption. While 5 -7 µm CdTe absorber layer absorbed more than 90% of the incident light with minimum series resistance. A complete CdS/CdTe solar cell was fabricated and tested. It was found that deposited cell without heat treatment shows that the short circuit current increment decreases as the light intensity increases. This type of deposited cell has low conversion efficiency. The energy conversion efficiency was improved by heat treatment, depositing heavily doped layer at the back of the cell and minimizing the contact resistivity by depositing material with resistivity less than 1 mΩ·cm 2 . All these modifications were not enough because the back contact is non-ohmic. Tunnel diode of CdTe (p++)/CdS (n++) was deposited in the back of the cell. The energy conver-sion efficiency was improved by more than 7%.
The present-day semiconductor technology would be inconceivable without extensive use of Schottky barrier junctions. In spite of an excellent book by Professor E.H. Rhoderick (1978) dealing with the basic principles of metal semiconductor contacts and a few recent review articles, the need for a monograph on "Metal-Semiconductor Schottky Barrier Junctions and Their Applications" has long been felt by students, researchers, and technologists. It was in this context that the idea of publishing such a monograph by Mr. Ellis H. Rosenberg, Senior Editor, Plenum Publishing Corporation, was considered very timely. Due to the numerous and varied applications of Schottky barrier junctions, the task of bringing it out, however, looked difficult in the beginning. After discussions at various levels, it was deemed appropriate to include only those typical applications which were extremely rich in R&D and still posed many challenges so that it could be brought out in the stipulated time frame. Keeping in view the larger interest, it was also considered necessary to have the different topics of Schottky barrier junctions written by experts.
Metal-semiconductor contacts showing rectifying properties are finding more and more applications in modern semiconductor devices technology(1) Apart from the fact that they are comparatively easy to fabricate and incorporate into integrated circuits, the main reason for their wide usage is that they do not exhibit minority carrier effects (e.g., long reverse recovery time, diffusion capacitance, etc.) similar to those observed in p-n junction devices. Various metal-semiconductor systems, investigated during the last two decades, are tabulated in Table 1. It can be seen from this table that the investigations are mainly centered round Schottky contacts based on Si and GaAs. Amongst the two, Si-based Schottky contacts are at present being used in a wide variety of devices and integrated circuits. Recent advances in GaAs material and processing techniques have, however, shown that not only can all of the semiconductor device structures realized in Si be fabricated in GaAs, but optical and very high speed integrated circuits can also be realized in the not-too-distant future. It is because of this as well as metallurgical and reliability considerations that the activity pertaining to GaAs-based Schottky contacts has increased appreciably during the last few years.
A new Cu/nn-InP Schottky junction with organic dye (PSP) interlayer has been formed by using a solution cast process. An effective barrier height as high as 0.82 eV has been achieved for Cu/PSP/nn-InP Schottky diodes, which have good current–voltage (I–V) characteristics. This good performance is attributed to the effect of formation of interfacial organic thin layer between Cu and nn-InP. By using capacitance–voltage measurement of the Cu/PSP/nn-InP Schottky diode the diffusion potential and the barrier height have been calculated as 0.73 V and 0.86 eV, respectively. From the I–V measurement of the diode under illumination, short circuit current (Isc) and open circuit voltage (Voc) have been extracted as 0.33 μA and 150 mV, respectively.
The feasibility of using amorphous silicon photodetectors as receivers in optical interconnection is discussed. The amorphous silicon could be deposited on top of the silicon chip so that the entire chip area could be dedicated to processor and memory circuits. Utilizing the parallelism afforded by fabricating arrays of large numbers of modulators and receivers would provide communication bandwidth far in excess of electronic interconnects even though individual receivers operated at modest speed. A preliminary experiment was carried out to determine important issues such as photosensitivity and interfacing between the amorphous silicon sensor and crystalline silicon circuit. The results show that amorphous silicon photodetectors have high photosensitivity. A bipolar-junction-transistor voltage comparator or CMOS inverter can be used to amplify the photocurrent generated by the detector to the level required by very large scale integration circuits. Systems using amorphous silicon detectors could offer large-bandwidth parallel communication channels for multiprocessors, based entirely on proven, compatible materials and processes.
In this work, we study the influence of the hydrogenated amorphous silicon (a-Si:H) surface treatment on the J–V characteristics of a-Si:H/Pd Schottky barrier photodiodes. The a-Si:H surface were etched, thermally oxidised and wet oxidised by H2O2. The a-Si:H films were characterised by spectroscopic ellipsometry, were we found that all the oxidation techniques promote an increase of the surface oxide thickness that was confirmed by the increase of the barrier height. The highest barrier was achieved by the H2O2 oxidation where a value of 1.17eV was found. As a result of the barrier height increase, the dark reverse current density decreases up to 10−10A/cm2 and the signal to noise ratio increases up to 106. The open circuit voltage under AM1.5 illumination conditions also increases from 0.4 to 0.5V. These results reveal the importance of the a-Si:H surface preparation prior to metallization to improve the Schottky photodiodes properties.
Recently, a lot of attention has been paid to Schottky barrier photo detectors due to their promising properties and easy of fabrication. Many samples of SB devices prepared by thermal deposition under high vacuum are studied in this research. Different types and thicknesses of oxides were deposited on silicon substrate. Metals of different types and thicknesses were deposited on top of oxides. Variation of photogenerated current, responsivity, quantum efficiency and detectivity as a function of incident light wavelength were measured. It was found that the shape of the curves has two maxima, one was around 500nm and the other was around 700nm. Ni (100)–SiO2–Si structure shows the maximum responsivity at 550nm and it is equal to 400mA/W. When comparison was made between devices of different metals, the nickel layer device showed high responsivity at visible region while the aluminum layer device showed high responsivity at near infrared region. Finally, the aluminum layer device showed detectivity higher than nickel layer device. The maximum detectivity of aluminum device was 6.4×1010cm/HzW.
The electronic structure of a jellium-Si interface is calculated using a jellium density corresponding to Al and self-consistent Si pseudopotentials. Local densities of states and charge densities are used to study states near the interface. At the Si surface, a high density of extra states is found in the energy range of the Si fundamental gap. These states are bulklike in jellium and decay into Si with a high concentration of charge in the dangling-bond free-surface-like Si state. Truly localized interface states are also found but at lower energies. The calculated barrier height is in excellent agreement with recent experimental results.