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Presents a study that proposed a theory for the junction capacitance of mathematically abrupt diodes. Derivation of a general junction capacitance formula; Information on a capacitance formula for an abrupt junction; Evaluation of the general capacitance formula for symmetrical and asymmetrical abrupt junction.

A model to calculate the current voltage characteristics of organic thin film transistors is presented. The model takes into account the influence of high electric field on trap occupancy. The case of the traps at a single energy level is considered in detail. Relevant equations are solved numerically using an iteration method. The field dependent trap occupancy model is found to change free surface charge Q[sub sf] and drain saturation current I[sub d] significantly. The model is compared with the experimental data published by two different groups. There is good agreement between experimental data and our model. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The space charge limited currents J in conducting organic materials often show J∼V[sup m] (where m > 2) dependence on voltage V. Two models have been used extensively to understand this behavior. In one model, the mobility μ is assumed to be dependent on electric field F. In the other model, an exponential distribution of traps is assumed and the mobility is taken to be independent of field. In this model the influence of the high electric fields present in organic polymers has not been taken into account. We present a model to calculate the J(V) characteristics for single carrier organic polymers taking into account the change in the occupancy of the traps due to the high electrical fields present in these materials. We show that the field dependent trap occupancy (FDTO) model can effectively explain the current-voltage characteristics reported by several different groups. If the FDTO model is used, it is not necessary to use the two different models mentioned above. [ABSTRACT FROM AUTHOR]

We improve the trapping model of carrier transport in conducting polymers by integrating the coupled Poisson and continuity equations numerically. In the case of exponentially distributed traps calculated log J vs 1/T plots are straight lines indicating that the activation of carriers to the extended states can be described by one single activation energy, E[sub eff]. The improved trapping model agrees well with the recent experimental data at high temperatures (i.e., near room temperature). At low temperatures the trapping model does not work since the available thermal energy is not sufficient to ionize the traps. We use the hopping mobility model at low temperatures. The model explains the low-temperature J-V characteristics well. This mechanism of charge carrier transport is similar to that used for interpreting experiments on inorganic amorphous materials. [ABSTRACT FROM AUTHOR]

Focuses on a study which detailed the calculation of the interaction energy of arrays of dislocations with nonperiodic distribution. Reason for conducting the calculations; Focus of studies on strain relaxation in pseudomorphic epilayers; Situation in which the calculated rate of strain relaxation on annealing the metastable layers at higher temperatures is increased.

Presents a study that have grown epitaxial layers of silicon-doped indium-arsenic-antimony by molecular-beam epitaxy on gallium arsenide (GaAs) and GaAs-coated silicon substrates. Absorption coefficient; Use of the fitted value of the Fermi level; Electron concentration.

Focuses on a study which determined the properties of doped and undoped amorphous silicon films deposited by the homogenous chemical vapor deposition (HOMOCVD) technique. Information on HOMOCVD; Methodology of the study; Results and discussion.

Studies band-gap narrowing of gallium arsenide as a function of doping concentration using photoluminescence spectroscopy on samples grown by molecular epitaxy. Technique used in measuring the band gap energy; Details on the experiment; Discussion on the results of the study.

Provides information on a study which examined the infrared response of polycrystalline and epitaxial cobalt silicon[sub2]/silicon Schottky diodes as a function of the silicide thickness. Influence of grain boundary scattering on the silicide; Quantum efficiency of the polycrystalline diodes.

Presents a study that examined the fabrication of conventional and electromagnetically casted multicrystalline silicon solar cells using different passivation schemes. Implementation of plasma-enhanced chemical-vapor-deposition; Information on multicrystalline silicon; Discussion on hydrogen plasma passivation.

Space charge limited currents in organic semiconductors are frequently observed to obey the power law J-V[SUPm] and are attributed to an exponential distribution of traps having two parameters, namely the characteristic distribution energy E[SUBt] and the trap concentration H[SUBt]. We determine these parameters from the J(V) characteristics at two or more temperatures reported in literature. [ABSTRACT FROM AUTHOR]

According to the approximate theory of transport in a conducting organic material containing exponential traps, ln J versus In V plots are straight lines with slope l= T[sub C]/T, where T[sub c] is the characteristic temperature of the trap distribution. It is assumed in this theory that the concentration P[sub t] of trapped holes is much larger than the concentrationp of free holes. Our experiments and recent literature results show that at high applied voltages the observed In d versus In V plots deviate from the straight lines and bend down. The numerical solution presented in this article shows that at high voltages the contribution of p to the space charge does not remain negligible. Calculated In d versus In V plots do bend down consistent with our experimental results. The current approaches the trap-filled limit asymptotically as the applied voltage approaches infinity. [ABSTRACT FROM AUTHOR]

We describe a high sensitivity measurement setup for the determination of recombination parameters in semiconductors at low levels of carrier injection. The setup is based on a lock-in amplifier and on a commercially available contactless conductivity detector. The information on recombination is extracted through the analysis, assuming quasi-steady-state conditions, of the low frequency, sinusoidally modulated photoconductivity signal induced by the illumination of a 950 nm light emitting diode array. Experimental results show a substantial increase in sensitivity with respect to traditional transient or quasi-steady-state techniques based on the same detection principle. The sensitivity bonus can be exploited for the extension of the carrier injection range for which effective recombination lifetime is measurable, both in the case of p-type and n-type wafers. [ABSTRACT FROM AUTHOR]

Up to now, all high frequency switching experiments on ferromagnetic semiconductors have involved light induced switching, which is not compatible with integrated circuits. We employed all-electrical techniques to study the response of (Ga,Mn)As to a magnetic field pulse. A field pulse was applied through a coplanar waveguide and the magnetization was read out by anisotropic magnetoresistance. We demonstrated that full magnetization switching by domain wall nucleation and propagation can be triggered by pulses as short as 800 ps, combining the effect of the pulsed field and a heat-induced reduction of the coercive field. [ABSTRACT FROM AUTHOR]

Most conducting organic materials have a background p-type doping varying in the range 10[sup 15]-10[sup 17] cm[sup -3]. We report results of a theoretical and experimental study of carrier transport in p-doped organic Schottky diodes. The theory given in this article shows that in a doped organic material with ohmic contacts the current is ohmic at low voltages. If the ohmic contact at the cathode is replaced by an Al Schottky contact the current varies exponentially with the applied voltage V. The current changes to space charge limited current (SCLC) at high voltages. The voltage at which the change takes place depends on the doping concentrations. In the SCLC regime the current varies according to the well-known V[sup 2] law if there are no traps and the mobility is independent of the electric field. If either trapping or effect of field on mobility is important, the current varies as V[sup m], where m>2. We have investigated experimentally the I-V characteristics of Schottky diodes fabricated using the PPV-based oligomer 2,5-di-n-octyloxy-1,4-bis (4′, 4″-bis-styryl) styrylbenzene (Ooct-OPV5) blended with polystyrene (PS) and the PPV-based polymer poly(2-methoxy-5-(3,7-dimethyloctyloxy)-p-phenylene vinylene) (OC[sub 1]C[sub 10]). As predicted by the theory, Al/Ooct-OPV5:PS/ITO (indium tin oxide) and Al/OC[sub 1]C[sub 10]/ITO Schottky diodes do show that the current varies exponentially with V at low voltages and as SCLC according to the V[sup m] law (with m=3) at high voltages. The V[sup 3] variation of the current in the SCLC regime can be due to trapping or field dependent mobility. It is not possible to distinguish unambiguously between the two mechanisms using the experimental results. The voltage at which transition from the Shockley current to SCLC takes place can be used to determine the background doping concentration. The p-type background doping concentration in the Ooct-OPV5 is found to be ∼10[sup 17] cm[sup -3]. From the tem... [ABSTRACT FROM AUTHOR]

Presents the preparation of polycrystalline silicon solar cells using a conventional diffusion and screen printed metallization method. Application of a dicing saw and beveled blades for the V-groove formation; Comparison with the standard nongrooved structure.

Examines the passivation of solar cells fabricated using casted multicrystalline silicon from Eurosolare. Description of the optimum passivation scheme; Increase of the efficacy of the solar cells with the combination of phosphorus gettering and read aluminum treatments.

Investigates the molecular beam epitaxial growth of InAsSb on gallium arsenide (GaAs)-coated patterned silicon (Si) substrates. Comparison of the InAsSb epilayer morphology for different substrate conditions; Threaded defect density of the InAsSb layers; Evidence of a regular array of misfit dislocations.

The influence of trace metal impurities of low-temperature undoped amorphous silicon by homogeneous chemical vapor deposited a-Si:H has been explored for the first time. The metal impurities Ni, Cr, and Fe cause a shift of the transition temperature for the double-activated regime to a relatively low value. However, Ga and B impurities quench the photoluminescence intensity at a low temperature. Both of them cause weak photoemission of the films at room temperature. The shift of the transition temperature can be explained by the presence of non-radiative deep recombination centers. The quenching of the photoluminescence intensity is caused by the presence of nonradiative recombination centers. [ABSTRACT FROM AUTHOR]

Novel methods of GaAs surface passivation are investigated. Passivation is acheived by simple chemical treatments using aqueous solutions of Na2S, KOH, RuCl3, and K2Se. GaAs pn homojunction solar cells are used to evaluate the effectiveness of these passivation techniques. A significant reduction in minority-carrier surface recombination velocity is demonstrated. In the best case, the surface recombination velocity decreased from 5×106 cm/s (untreated surface) to 103 cm/s. In addition, we observe improvements in solar cell photogenerated current, short wavelength spectral response, open-circuit voltage, and junction ‘‘dark’’ current. [ABSTRACT FROM AUTHOR]

A gallium arsenide film is grown embedded in masked pre-etched wells in silicon vicinal (001) substrates by molecular beam epitaxy. The morphology and crystallinity of the embedded GaAs on Si layers are identical to those of large area GaAs on Si grown on the same wafer, as indicated by the comparison of Nomarski contrast photomicrographs and electron channeling patterns. High-resolution electron microscope images reveal the epitaxial relation of the GaAs/Si interface on the bottom and the sidewall of the wells. On the slope most of the dislocations are restricted to a narrow region near the interface. The same photoluminescent behavior is found for the GaAs deposit in the different silicon environments. This embedded growth technique is suitable for realization of a coplanar GaAs on Si surface. [ABSTRACT FROM AUTHOR]

Epitaxial growth of phosphorus-doped silicon deposited at 250 °C from a radio-frequency glow discharge from SiH4 is demonstrated by high-resolution electron microscopy (HREM) and spreading resistance profile measurements. Thin epitaxial films are present at the interface between (100) Si substrates and hydrogenated amorphous silicon. After recrystallization at 700 °C, single-crystal layers are obtained, in which HREM reveals extensive twinning. The fact that epitaxial growth can take place at 250 °C in a system with a background pressure of only 5×10-6 mbar can be attributed to the presence of species in the SiH4 plasma that reduce the native oxide and the use of HF in the cleaning procedure. [ABSTRACT FROM AUTHOR]

Describes a fabrication process for blue response improvement in low-cost polycrystalline silicon solar cells. Creation of a selective emitter; Comparison of the parameters of solar cells with different types of emitters; Advantages of the proposed process.