Space Charge Region Of Si Research Articles

Electric-Field-Induced Second-Harmonic Generation Demonstrates Different Interface Properties of Molecular Beam Epitaxy Grown MgO on Si

The ability to tune the electrical properties of a metal–oxide–semiconductor structure, especially the chemical nature and the associated electrical properties of the first few layers of the oxide, is of increasing importance in the semiconductor industry. Oxide deposition using molecular beam epitaxy facilitates the control of the interface with the semiconductor at the atomic level. Depending on the characteristics of the first monolayer, the electric-field-induced second-harmonic generation can be shifted, which is correlated to the flat-band voltage shift. Three different oxide–semiconductor interfaces, which originate from different first monolayers, are investigated by electric-field-induced second-harmonic generation and are shown to exhibit different electronic characteristics. Migration of positive oxygen vacancies from the oxide layer toward the Si space-charge region is observed.

Electrical characteristics of DNA-based metal-insulator-semiconductor structures

High quality sandwich device was fabricated from wheat DNA molecular film by solution processing located between Au and n-type silicon inorganic semiconductor. We have performed the electrical characteristics of the device such as current–voltage (I–V) and capacitance–voltage (C–V) at room temperature. DNA-based on this structure showed an excellent rectifying behavior with a typical ideality factor of 1.22, and that DNA film increased the effective barrier height by influencing the space charge region of Si. We proposed that DNA could be an insulatorlike material with a wide optical band energy gap of 4.19 eV from its optical absorbance characteristics. Additionally, the energy distribution of interface state density, determined from the forward bias I–V characteristics by taking into account the bias dependence of the effective barrier height, decreases exponentially with bias from 7.48×1015 m−2 eV−1 in (Ec−0.40) eV to 8.56×1014 m−2 eV−1 in (Ec−0.72) eV.

Electrical analysis of organic dye-based MIS Schottky contacts

In this work, we prepared metal/interlayer/semiconductor (MIS) diodes by coating of an organic film on p-Si substrate. Metal(Al)/interlayer(Orange G OG)/semiconductor( p-Si) MIS structure had a good rectifying behavior. By using the forward-bias I– V characteristics, the values of ideality factor ( n) and barrier height (BH) for the Al/OG/ p-Si MIS diode were obtained as 1.73 and 0.77 eV, respectively. It was seen that the BH value of 0.77 eV calculated for the Al/OG/ p-Si MIS diode was significantly larger than the value of 0.50 eV of conventional Al/ p-Si Schottky diodes. Modification of the potential barrier of Al/ p-Si diode was achieved by using thin interlayer of the OG organic material. This was attributed to the fact that the OG organic interlayer increased the effective barrier height by influencing the space charge region of Si. The interface-state density of the MIS diode was found to vary from 2.79 × 10 13 to 5.80 × 10 12 eV −1 cm −2.

Electronic properties of the metal/organic interlayer/inorganic semiconductor sandwich device

In this study, we prepared a Metal(Al)/Organic Interlayer(Congo Red=CR)/Inorganic Semiconductor ( p-Si) (MIS) Schottky device formed by coating of an organic film on p-Si semiconductor wafer. The Al/CR/ p-Si MIS device had a good rectifying behavior. By using the forward bias I– V characteristics, the values of ideality factor ( n) and barrier height ( Φ b ) for the Al/CR/ p-Si MIS device were obtained as 1.68 and 0.77 eV, respectively. It was seen that the Φ b value of 0.77 eV calculated for the Al/CR/ p-Si MIS device was significantly higher than value of 0.50 eV of the conventional Al/ p-Si Schottky diodes. Modification of the interfacial potential barrier of the Al/ p-Si diode was achieved by using a thin interlayer of the CR organic material. This was attributed to the fact that the CR organic interlayer increased the effective barrier height by influencing the space charge region of Si. The interface-state density of the MIS diode was found to vary from 1.24×10 13 to 2.44×10 12 eV −1 cm −2.

Laterally inhomogeneous barrier analysis of the methyl violet/p-Si organic/inorganic hybrid Schottky structures

In this work, we have investigated the electrical characteristics, such as current–voltage ( I–V) and capacitance–voltage ( C– V) measurements, of identically prepared crystal violet/p-Si Organic/Inorganic (OI) Schottky structures formed by evaporation of organic compound solution to directly p-Si semiconductor substrate. It has been seen that the crystal violet organic dye thin film on the p-Si substrate has exhibited a good rectifying behavior. The barrier heights (BHs) and ideality factors of all devices have been calculated from the electrical characteristics. Although the diodes were all identically prepared, there was a diode-to-diode variation: the effective barrier heights ranged from 0.6 ± 0.1 to 0.8 ± 0.1 eV, and the ideality factor from 1.6 ± 0.4 to 3.5 ± 0.4. The barrier height versus ideality factor plot has been plotted for the OI devices. Lateral homogeneous BH was calculated as a value of 0.7 eV from the observed linear correlation between BH and ideality factor, which can be explained by laterally inhomogeneities of BHs. The values of barrier height and acceptor doping concentration yielded from the reverse bias C– V measurements ranged from 0.7 ± 0.1 to 1.3 ± 0.1 eV and from (4.7 ± 0.8) × 10 14 to (8.1 ± 0.8) × 10 14 cm −3, respectively. The mean barrier height and mean acceptor doping concentration from C– V characteristics has been calculated 1.0 eV and 5.9 × 10 14 cm −3, respectively. It has been seen that the mean BH value of 0.7 eV obtained for the Al/methyl violet/p-Si contact is significantly larger than BH values of the conventional Al/p-Si Schottky diodes. Thus, modification of the interfacial potential barrier for metal/Si diodes has been achieved using a thin interlayer of the methyl violet organic semiconductor; this has been ascribed to the fact that the methyl violet interlayer increases the effective barrier height by influencing the space charge region of Si.

Current-voltage and capacitance-voltage characteristics of Sn/rhodamine-101∕n-Si and Sn/rhodamine-101∕p-Si Schottky barrier diodes

The nonpolymeric organic compound rhodamine-101 (Rh101) film on a n-type Si or p-type Si substrate has been formed by means of the evaporation process and the Sn/rhodamine-101/Si contacts have been fabricated. The Sn∕Rh101∕n-Si and Sn∕Rh101∕p-Si contacts have rectifying contact behavior with the barrier height (BH) values of 0.714 and 0.827eV, and with ideality factor values of 2.720 and 2.783 obtained from their forward bias current-voltage (I-V) characteristics at room temperature, respectively. It has been seen that the BH value of 0.827eV obtained for the Sn∕Rh101∕p-Si contact is significantly larger than BH values of the conventional Sn∕p-Si Schottky diodes and metal/interfacial layer/Si contacts. Thus, modification of the interfacial potential barrier for metal/Si diodes has been achieved using a thin interlayer of the Rh101 organic semiconductor; this has been ascribed to the fact that the Rh101 interlayer increases the effective barrier height by influencing the space charge region of Si.

Second-harmonic generation from Si∕SiO2∕Hf(1−x)SixO2 structures

Optical second-harmonic generation (SHG) is used to characterize thin films of Hf(1−x)SixO2 (x=0, 0.3, 0.45, 0.65, and 1) deposited by atomic layer epitaxy at 375°C on Si substrates with 11Å SiO2 buffer layers. Reflected SHG intensity measured at room temperature increases monotonically with Hf content for as-deposited samples and varies strongly with the temperature (600–1000°C) of postdeposition rapid anneals in NH3. Spectroscopic analysis shows that the variable SHG component peaks at SH photon energy of 3.37eV—the bulk silicon E1 critical point energy—a clear signature of electric-field-induced second-harmonic generation in the bulk Si space-charge region. The results suggest that SHG is a sensitive, potentially in situ, probe of internal electric fields attributable to composition- and annealing-dependent fixed charge in the oxide layers.

A manifestation of the tunneling conductivity of a thin-gate insulator in the generation kinetics of minority carriers in metal-insulator-semiconductor structures

The kinetics of the minority-charge-carrier generation current I(t), in the Al-n+-Si-SiO2-n-Si structures with a tunnel-transparent oxide layer, are found to be anomalous. Under depleting gate potentials (Vg<0), sharp peaks are observed in the I(t) curves, whose descending branches attain a steady-state current level rapidly increasing with |Vg|. The observed features are related to the tunneling conductivity of a thin (100 A) oxide layer and with the impact generation of electron-hole pairs in a space charge region of Si by hot electrons that tunnel into the space charge region. Using this concept, an algorithm of the quantitative description of the experimental data is developed. This algorithm makes it possible to separate the components related to thermal and impact generation and the tunneling current component from the total current I(t). The impact ionization factor (α=1.2±0.2) and the energy of hot electrons in Si space charge region (Eim=4.23 eV) are determined. Dynamic and steady-state current-voltage characteristics for the oxide layer coincide and obey the Fowler-Nordheim law. The position of the current maximum is controlled by external factors that stimulate the generation of non-equilibrium charge carriers; this effect can be used for the development of integrating and threshold sensors.

A Quantitative Model of the Electrical Activity of Metal Silicide Precipitates in Silicon Based on the Schottky Effect

ABSTRACTA quantitative model of the electrical activity of metallic precipitates in Si is presented. An emphasis is placed on the properties of the Schottky junction at the precipitate-Si interface, as well as the carrier diffusion and drift in the Si space charge region. Carrier recombination rate is found to be primarily determined by the thermionic emission charge transport process across the Schottky junction rather than the surface recombination process. It is shown that the precipitates can have a very large minority carrier capture cross-section.

Schottky effect model of electrical activity of metallic precipitates in silicon

A quantitative model of the electrical activity of metallic precipitates in Si is formulated with an emphasis on the Schottky junction effects of the precipitate–Si system. Carrier diffusion and carrier drift in the Si space charge region are accounted for. Carrier recombination is attributed to the thermionic emission mechanism of charge transport across the Schottky junction rather than the surface recombination. It is shown that the precipitates can have a very large minority carrier capture cross-section. Under weak carrier generation conditions, the supply of minority carriers is found to be the limiting factor of the recombination process. The plausibility of the model is demonstrated by a comparison of calculated and available experimental results.

Analysis of the rate of change of inversion charge in thin insulator p-type Metal-Oxide-Semiconductor structures

A model of the rate of change of inversion charge has been used to investigate the capacitance relaxation associated with Fowler-Nordheim tunneling current in thin insulator p-type Metal-Oxide-Semiconductor (MOS) structures. In this model, the rate of change of inversion charge is taken to be equal to the difference between the generation current in the space charge region of Si and the Fowler-Nordheim tunneling current through the oxide. Using a step voltage, analytical expression for high frequency capacitance relaxation is obtained, the experimental results are consistent with model calculations.

Photoelectrochemical Cells of the Electrolyte‐Metal‐Insulator‐Semiconductor (EMIS) Configuration: I . Metal Thickness and Coverage Effects in the Pt/Silicon Oxide/n‐Si System

We have studied photoelectrodes of the type Pt/silicon oxide/n‐Si in both aqueous iodine and bromine solutions in order to elucidate the role of the thin Pt overlayer and the thermally grown tunnel oxide. We have shown that it is possible to produce Pt coatings 10Å thick having at least 99% coverage, which provide substantial corrosion protection, while not reducing the influence of the redox solution in determining the open‐circuit voltage of the cells. However, for Pt films 20 and 40Å thick, the open‐circuit voltages were independent of the redox potential of the solution. The origins of these effects are discussed. Using C‐V and I‐V measurements, we have established the absence of kinetic barriers at the Pt‐solution interface, which thus enabled the semiconductor‐oxide junctions to be electrically characterized. In an 8% efficient photoelectrode, the tunnel coefficient through the oxide was approximately 0.1. The bucking current resulted in a loss of approximately 0.2V from the theoretical open‐circuit voltage. The combination of fixed oxide charge and interface states resulted in a further loss of 0.2V, to give an observed maximum value of the open‐circuit voltage of 0.42V. Finally, the bucking current analyses showed that, for electrodes coated with 10Å Pt, the dominant current arose from thermionic emission over the barrier in the Si, whereas, for the electrodes coated with 20 and 40Å Pt, recombination in the Si space charge region dominated, suggesting that the higher surface temperatures reached during deposition of the thicker Pt coatings caused diffusion of Pt recombination centers into the space charge region, as corroborated by other evidence.

Electronic properties of the annealed interface between Ag and 7 × 7 Si(111)

Photoemission yield spectroscopy measurements, associated with LEED and Auger characterisation, are performed on a set of silicon (111) surfaces with different bulk dopings as a function of silver coverage theta , from zero to a few monolayers, obtained by UHV evaporation on a sample kept at room temperature then annealed at 500 degrees C. When the square root 3 × square root 3 structure which is completed theta c approximately=2/3 monolayer is substituted for the 7 × 7 LEED pattern the work function of the system does not vary significantly, while the ionisation energy decreases by about 0.5 eV; it corresponds to a band-bending variation in the Si space-charge region that is in agreement with the change of surface-state density in the gap. The persistence of a Si dangling-bond peak after completion of the first silver layer favours models where a two-dimensional ordered layer is formed allowing Si atoms to be at the surface.