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Despite the widespread use of tunnel junctions in high-efficiency devices (e.g., multijunction solar cells, tunnel field effect transistors, and resonant tunneling diodes), simulating their behavior still remains a challenge. This paper presents a new model to complete that of Karlovsky and simulate an I (V) characteristic of an Esaki tunnel junction. A review of different analytical models of band-to-band tunneling models is first presented. As a complement to previous work on tunnel junction simulation, the transmission coefficient is precisely determined and incorporated, the valley current between the tunneling and drift regimes is included, and calculations of physical parameters are updated. It is found that the model works for a broad range of values of the forward bias. [ABSTRACT FROM AUTHOR]

This paper investigates the importance of incomplete ionization of dopants in compensated p-type Si and its impact on the majority-carrier density and mobility and thus on the resistivity. Both theoretical calculations and temperature-dependent Hall-effect measurements demonstrate that the carrier density is more strongly affected by incomplete ionization in compensated Si than in uncompensated Si with the same net doping. The previously suggested existence of a compensation-specific scattering mechanism to explain the reduction of mobility in compensated Si is shown not to be consistent with the T-dependence of the measured carrier mobility. The experiment also shows that, in the vicinity of 300 K, the resistivity of compensated Si has a much weaker dependence on temperature than that of uncompensated silicon. [ABSTRACT FROM AUTHOR]

Compensation effects are intensively studied on two highly doped ingots grown from solar-grade silicon feedstocks purified using metallurgical routes, through a comparison of the electrical properties at iso-carrier densities. Working at given carrier densities enables a clearer extraction of the compensation effects, at the wafer and solar cell levels. At the wafer level, the majority carrier mobility and the carrier lifetime are investigated. Regarding the mobilities, it was found that current models may underestimate the amount of incomplete ionization of boron leading to underestimated mobilities. In addition, the majority carrier mobility was found to be strongly affected at high compensation level. Regarding the carrier lifetimes, our results show that after a phosphorus diffusion step, dopants alone - and especially boron - can limit the lifetime in highly doped solar-grade silicon. At the cell level, I-V characteristics under standard illumination were studied. In particular, the observed reductions in short-circuit current on solar cells having a very high compensation level could be explained in terms of a compensation-induced reduction in the minority carrier mobility. We also report high conversion efficiencies of up to 15.9% on solar cells showing a boron content greater than two ppmw (2.6 × 1017 cm-3), which is generally considered unsuitable for solar cell manufacturing. [ABSTRACT FROM AUTHOR]

The Al/TiO[SUBx]/Si, Ti/TiO[SUBx]/Si, and Mo/TiO[SUBx]/Si interfaces are studied, before and after thermal treatment, by secondary ion mass spectrometry (SIMS), Rutherford backscattering spectrometry (RBS), x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and scanning electron microscopy. The metal layer is selected with regard to the formation of a titanium silicide layer. The reductive nature of the metal was found to be very significant in the interdiffusion of Si and Ti (from titanium oxide). This interdiffusion has the advantage to form a thin titanium silicide layer, which is known to have low contact resistivity. The SIMS, RBS, XPS, and XRD analyses show that after annealing for 10 min at 850°C under hydrogen ambient, titanium silicide interfacial layers such as Ti[SUB5]Si[SUB3] and TiSi[SUB2] C54 were formed in the case of Al/TiO[SUBx]/Si and Ti/TiO[SUBx]/Si structures, respectively. There is no significant reaction between Mo and TiO[SUBx] and no Ti and Si interfacial reaction in the Mo/TiO[SUBx]/Si system. With thermodynamic considerations, we confirm all the results found in this study. [ABSTRACT FROM AUTHOR]

Investigates the structural, electrical and piezoresistive properties of in situ boron-doped thin silicon layers deposited by plasma-enhanced chemical-vapor deposition on oxidized silicon substrates and subjected to a rapid thermal anneal. Sample preparation and experimental methods; Stress and structure of the films; Effect of doping on optical properties.

Mesoporous germanium (Ge) is a new nanostructured material with a very high potential for numerous applications. Thermally induced structural evolution of this nanomaterial is a key point for many high-temperature processes, such as epitaxy, for example, in which it can be involved. In this work, we investigate these structural changes occurring during thermal annealing in vacuum in temperature range between 250 and 650 °C. The influences of the annealing temperature and time as well as of the initial porous layer thickness on the morphology reorganization of the mesoporous Ge layer are described in detail. The obtained results are discussed in terms of Lifshitz-Slyozov-Wagner theory. [ABSTRACT FROM AUTHOR]

The size of silicon quantum dots (Si QDs) embedded in silicon nitride (SiNx) has been controlled by varying the total pressure in the plasma-enhanced chemical vapor deposition (PECVD) reactor. This is evidenced by transmission electron microscopy and results in a shift in the light emission peak of the quantum dots. We show that the luminescence in our structures is attributed to the quantum confinement effect. These findings give a strong indication that the quality (density and size distribution) of Si QDs can be improved by optimizing the deposition parameters which opens a route to the fabrication of an all-Si tandem solar cell. [ABSTRACT FROM AUTHOR]

Interconnected Si nanocrystals forming homogeneous thin films with controlled bandgap values from 1.2 to 2.9 eV were formed by pulsed plasma enhanced chemical vapor deposition technique under dusty plasma conditions. The chosen values of plasma duration time correspond to specific phases of the dust nanoparticle growth. Structural and optical properties of the deposited nanostructured films are described in details. These nanocrystalline Si thin films seem to be promising candidates for all-Si tandem solar cell applications. [ABSTRACT FROM AUTHOR]

This paper reports on an enzymatic organic field effect transistor based biosensor dedicated to the detection of trimethylamine, in view of fish freshness assessment. Flexible devices were processed on Kapton substrate with pentacene as organic semiconductor and Parylene-C as top gate dielectric. Proton sensitive dielectric surface was achieved by depositing a thin hydrogenated silicon nitride layer at moderate temperature on Parylene. An enzymatic membrane made of flavin-containing mono-oxygenase 3 cross-linked with bovine serum albumin deposited on silicon nitride completed the realization of the device. High sensitivity trimethylamine biosensing was demonstrated in the 0–8 ppm range. [ABSTRACT FROM AUTHOR]

We report on the realization of flexible ion sensitive organic field effect transistors based on pentacene on which Parylene-C was deposited as top gate dielectric. In order to create proton sensitive sites at the insulator/electrolyte interface, Parylene-C surface has been covered with a thin layer of hydrogenated silicon nitride (SiN:H) deposited by photochemical vapor deposition at moderate temperature. The combination of Parylene and SiN:H enables the realization of highly reproducible and good performance transistors as well as ion sensitive sensors with an excellent pH response both in the acidic and alkaline pH range in a nearly all plastic technology. [ABSTRACT FROM AUTHOR]

Experimental investigation of photoconductivity in Si-rich silicon oxide (SRSO)/SiO2 multilayer (ML) structures prepared by magnetron reactive sputtering is reported. Photocurrent (PC) measurements show that the PC threshold increases with decreasing the thickness of SRSO layer. Photo-conduction processes in our samples are shown to be dominated by carrier transport through quantum-confined silicon nanocrystals embedded in the SiO2 host. In addition, the observed bias-dependence of photocurrent intensity is consistent with a model in which carrier transport occurs by both tunneling and hopping through defect states in the silicon oxide matrix. A photocurrent density Jph of 1-2 mA cm-2 is extracted from our results. Although this photocurrent density along the ML absorber film is relatively low, the results presented in this work are believed to be a valuable contribution toward the implementation of all-Si tandem solar cells. [ABSTRACT FROM AUTHOR]