Carrier Concentration (carrier + concentration)

Distribution by Scientific Domains
Distribution within Physics and Astronomy

Kinds of Carrier Concentration

  • charge carrier concentration
  • free carrier concentration


  • Selected Abstracts


    Growth and electrical properties of flash evaporated AgGaTe2 thin films

    CRYSTAL RESEARCH AND TECHNOLOGY, Issue 2 2006
    B. H. Patel
    Abstract Thin films have been prepared by flash evaporation technique of a stoichiometric bulk of AgGaTe2 compound in vacuum and analysed using X-ray diffraction, transmission electron microscopy, selected area diffraction and energy dispersive analysis of X-rays. The effect of substrate temperature on the structural properties , grain size, film orientation, composition, and stoichiometry of the films have been studied. It was found that the polycrystalline, stoichiometric films of AgGaTe2 can be grown in the substrate temperature range of 473K < Ts < 573K. The influence of substrate temperature (Ts) on the electrical characteristics- Resistivity, Hall Mobility, Carrier concentration of AgGaTe2 thin films were studied. The electrical resistivity was found to decrease with increase in substrate temperature up to 573K and then increases. The variation of activation energy of AgGaTe2 thin films were also investigated. The implications are discussed. ( 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Physical properties of Dy and La doped SnO2 thin films prepared by a cost effective vapour deposition technique

    CRYSTAL RESEARCH AND TECHNOLOGY, Issue 10 2006
    J. Joseph
    Abstract Stannous oxide (SnO2) thin film is one of the most widely used n-type transparent semi-conductor films in electronics, electro-optics and solar energy conversion. By achieving controlled non-stoichiometry, we can get good transparency and high electrical conductivity simultaneously in SnO2 thin films. Dy and La doped SnO2 thin films have been prepared by a cost effective vapour deposition technique. The structural, photo-electronic, optical and electrical properties of the doped and undoped films were studied. The results of X-ray Diffraction studies reveals the polycrystalline nature of the films with preferential orientation along the (101), (211) and (301) planes and their average grain size variation for different deposition temperature. Photoconductivity and Photovoltaic studies of the films were also performed. The optical properties of these films were studied by measuring their optical transmission as a function of wavelength. The optical transmission is found to be increased on Dy doping and decreased on La doping. The band gap, refractive index and thickness of the films were calculated from U-V transmittance and Absorption graphs. The optical band gap of undoped film is found to be 4.08 eV, but on doping it shifts to lower energies and then increases on increasing the concentration of both dopants. Its electrical parameters such as sheet resistance, resistivity, mobility, Hall coefficient, and carrier concentration were determined by Four Probe, Van der Pauw and Hall Probe method. On doping with Dy, carrier conversion takes place from n-type to p-type and p-conductivity dominates. On La doping no carrier conversion takes place but resistivity decreases. ( 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Traversing the Metal-Insulator Transition in a Zintl Phase: Rational Enhancement of Thermoelectric Efficiency in Yb14Mn1,xAlxSb11,

    ADVANCED FUNCTIONAL MATERIALS, Issue 18 2008
    Eric S. Toberer
    Abstract For high temperature thermoelectric applications, Yb14MnSb11 has a maximum thermoelectric figure of merit (zT) of ,1.0 at 1273,K. Such a high zT is found despite a carrier concentration that is higher than typical thermoelectric materials. Here, we reduce the carrier concentration with the discovery of a continuous transition between metallic Yb14MnSb11 and semiconducting Yb14AlSb11. Yb14Mn1-xAlxSb11 forms a solid solution where the free carrier concentration gradually changes as expected from the Zintl valence formalism. Throughout this transition the electronic properties are found to obey a rigid band model with a band gap of 0.5,eV and an effective mass of 3 me. As the carrier concentration decreases, an increase in the Seebeck coefficient is observed at the expense of an increased electrical resistivity. At the optimum carrier concentration, a maximum zT of 1.3 at 1223,K is obtained, which is more than twice that of the state-of-the-art Si0.8Ge0.2 flown by NASA. [source]


    Charge Transport Physics of Conjugated Polymer Field-Effect Transistors

    ADVANCED MATERIALS, Issue 34 2010
    Henning Sirringhaus
    Abstract Field-effect transistors based on conjugated polymers are being developed for large-area electronic applications on flexible substrates, but they also provide a very useful tool to probe the charge transport physics of these complex materials. In this review we discuss recent progress in polymer semiconductor materials, which have brought the performance and mobility of polymer devices to levels comparable to that of small-molecule organic semiconductors. These new materials have also enabled deeper insight into the charge transport physics of high-mobility polymer semiconductors gained from experiments with high charge carrier concentration and better molecular-scale understanding of the electronic structure at the semiconductor/dielectric interface. [source]


    Antioxidative activity of rosemary extract using connective tissue proteins as carriers

    INTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 8 2008
    Katarzyna Waszkowiak
    Summary In the research the activity of rosemary extract introduced using connective tissue proteins was investigated, taking into consideration the effect of the type of carrier (collagen and elastin), carrier concentration (1%, 2%, 4%) and the method of its introduction to fat substrate (rehydrated or unhydrated). Antioxidative activity was assessed using the Oxidograph instrumental test. The activity of rosemary extract on protein preparations was significantly affected by the rehydration of these preparations. The application of collagen as carrier of rosemary extract had an advantageous effect on the activity of this antioxidant. In turn, under the adopted testing conditions the application of elastin resulted in partial masking of antioxidative activity of rosemary extract. Amounts of the carriers, onto which the antioxidant was introduced, did not have a statistically significant effect on this activity. [source]


    Atomistic analysis of B clustering and mobility degradation in highly B-doped junctions

    INTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 4-5 2010
    Maria Aboy
    Abstract In this paper we discuss from an atomistic point of view some of the issues involved in the modeling of electrical characteristics evolution in silicon devices as a result of ion implantation and annealing processes in silicon. In particular, evolution of electrically active dose, sheet resistance and hole mobility has been investigated for high B concentration profiles in pre-amorphized Si. For this purpose, Hall measurements combined with atomistic kinetic Monte Carlo atomistic simulations have been performed. An apparent anomalous behavior has been observed for the evolution of the active dose and the sheet resistance, in contrast to opposite trend evolutions reported previously. Our results indicate that this anomalous behavior is due to large variations in hole mobility with active dopant concentration, much larger than that associated to the classical dependence of hole mobility with carrier concentration. Simulations suggest that hole mobility is significantly degraded by the presence of a large concentration of boron-interstitial clusters, indicating the existence of an additional scattering mechanism. Copyright 2009 John Wiley & Sons, Ltd. [source]


    A new approach for numerical simulation of quantum transport in double-gate SOI

    INTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 6 2007
    Tarek M. Abdolkader
    Abstract Numerical simulation of nanoscale double-gate SOI (Silicon-on-Insulator) greatly depends on the accurate representation of quantum mechanical effects. These effects include, mainly, the quantum confinement of carriers by gate-oxides in the direction normal to the interfaces, and the quantum transport of carriers along the channel. In a previous work, the use of transfer matrix method (TMM) was proposed for the simulation of the first effect. In this work, TMM is proposed to be used for the solution of Schrodinger equation with open boundary conditions to simulate the second quantum-mechanical effect. Transport properties such as transmission probability, carrier concentration, and I,V characteristics resulting from quantum transport simulation using TMM are compared with that using the traditional tight-binding model (TBM). Comparison showed that, when the same mesh size is used in both methods, TMM gives more accurate results than TBM. Copyright 2007 John Wiley & Sons, Ltd. [source]


    Time domain global modelling of EM propagation in semiconductor using irregular grids

    INTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 4 2002
    Hsiao-Ping Tsai
    Abstract A two-dimensional finite volume time domain (FVTD) method using a triangular grid is applied to the analysis of electromagnetic wave propagation in a semiconductor. Maxwell's equations form the basis of all electromagnetic phenomena in semiconductors and the drift-diffusion model is employed to simulate charge transport phenomena in the semiconductor. The FVTD technique is employed to solve Maxwell's equations on an irregular grid and the finite box method is implemented on the same grid to solve the drift-diffusion model for carrier concentration. The locations of unknowns have been chosen to allow linking coupled Maxwell's equations and transport equations in a seamless way. To achieve suitable accuracy and computational efficiency, using irregular grid topology allows a finer mesh in doped region and at junction, and a coarser mesh in substrate and insulting regions. The proposed scheme has been implemented and verified by characterizing electromagnetic wave propagation at microwave frequency in a semiconductor slab with arbitrary doping profile. Copyright 2002 John Wiley & Sons, Ltd. [source]


    Liquid,liquid extraction of cadmium(II) by Cyanex 923 and its application to a solid-supported liquid membrane system

    JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 9 2005
    Ana Mara Rodrguez
    Abstract The extraction of cadmium(II) by Cyanex 923 (a mixture of alkylphosphine oxides) in Solvesso 100 from hydrochloric acid solution has been investigated. The extraction reaction is exothermic. The numerical analysis of metal distribution data suggests the formation of CdCl2.2L, HCdCl3.2L and H2CdCl4.2L (L = ligand) in the organic phase. The results obtained for cadmium(II) distribution have been implemented in a solid-supported liquid membrane system. The influences of feed phase stirring speed (400,1400 min,1), membrane composition (carrier concentration: 0.06,1 mol dm,3) and metal concentration (0.01,0.08 g dm,3) on cadmium transport have been investigated. Copyright 2005 Society of Chemical Industry [source]


    Optical and Electrical Properties of Amorphous and Nanocrystalline (La0.8Sr0.2)0.9MnO3 Thin Films Prepared from Low-Temperature Processing Technique

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2006
    Toshio Suzuki
    The results of a study on the optical and electrical properties of (La0.8Sr0.2)0.9MnO3 (LSM) thin films obtained by a polymeric precursor spin coating technique were presented. This method allowed preparation of optical quality thin films at annealing temperatures around 800C. Amorphous and crystalline LSM thin films were studied by optical and electrical conductivity measurements. The energy-dependent absorption coefficients for the crystalline specimen were calculated from optical spectra and extra absorption was observed in the range of 1.8,2.5 eV with the exchange-gap excitation behavior in the 3,5 eV range. In comparison to the amorphous specimens, the electrical conductivity of the nanocrystalline specimen increased two to three orders of magnitude with decreasing activation energy. The charge carrier absorption model suggested an increase of the carrier concentration in the nanocrystalline specimen which may be a reason for the change in the electrical conductivity. [source]


    Enhanced Properties of Tin(IV) Oxide Based Materials by Field-Activated Sintering

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2003
    Oana Scarlat
    The densification of SnO2 (0.9 mol),Sb2O3 (0.1 mol) solid solution without any additives was studied by conventional and field-activated sintering technique (FAST). FAST sintering achieved a relative density value of 92.4% at 1163 K for 10 min versus 61.3% in conventional sintering at 1273 K for 3 h. An abnormal reduction of the IR transmittance and a semiconductor defect structure with only one donor level in the SnO2 energy gap were noticed in the FAST-sintered as compared with the conventionally sintered Sn0.82Sb0.18O2 solid solution. A high charge carrier concentration (i.e., electronic conduction) was shown in the FAST-sintered sample by conductivity measurements and the negative values of the Seebeck coefficient. [source]


    Highly conductive and optically transparent GZO films grown under metal-rich conditions by plasma assisted MBE

    PHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 3-4 2010
    H. Y. Liu
    Abstract We demonstrate a critical effect of a metal-to-oxygen ratio on the electrical, optical, and structural properties of ZnO films heavily doped with Ga (carrier concentration in the range of 1020,1021 cm,3) grown by plasma-assisted molecular beam epitaxy. The as-grown layers prepared under the metal-rich conditions exhibited resistivities below 3 10,4 , cm and an optical transparency exceeding 90% in the visible spectral range as well as a large blue shift of the transmission/absorption edge attributed to the Burstein,Moss shift of the Fermi level deep into the conduction band, indicating high donor concentration. In contrast, the films grown under the oxygen-rich conditions required thermal activation and showed inferior properties. Furthermore, electrical measurements point to the nonuniform depth distribution of free carriers. An oxygen-pressure-dependent surface disordering is suggested to be responsible for the drastic effect of the metal-to-oxygen ratio on the film properties. ( 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Optical properties of InN grown on templates with controlled surface polarities

    PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 10 2010
    Ronny Kirste
    Abstract The structural and optical properties of InN layers grown on GaN/sapphire templates with controlled Ga-/N-polar surfaces are investigated. Raman spectroscopy and XRD reciprocal space map analysis suggest that the InN layers were grown strain free with a high crystal quality. A line shape analysis of the A1(LO) Raman mode yields to a decreasing carrier concentration for the sample grown on Ga-polar substrate. Low temperature photoluminescence measurements exhibit a shift to lower energies of the luminescence maximum for the sample grown on Ga-polar GaN probably due to a reduced carrier concentration and thus, a decreased Burstein,Moss shift. Following this, we demonstrate that the use of polarity controlled GaN/sapphire substrates leads to unstrained layers with good structural and optical properties. [source]


    The effect of oxygen remote plasma treatment on ZnO TFTs fabricated by atomic layer deposition

    PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2010
    Seungjun Lee
    Abstract We deposited ZnO thin films by atomic layer deposition (ALD) and then investigated the chemical and electrical characteristics after plasma treatment. The chemical bonding states were examined by X-ray photoelectron spectroscopy (XPS). The XPS spectra of O 1s showed that the intensity of oxygen deficient regions of the ZnO film decreased from 27.6 to 19.4%, while the intensity of the oxygen bound on the surface of the ZnO film increased from 15.0 to 21.9% as plasma exposure times increased. The ZnO film exhibited a decrease in carrier concentration from 4.9,,1015 to 1.2,,1014,cm,3 and an increase in resistivity from 1.2,,102 to 9.8,,103,,,cm as the plasma exposure times increased. To verify the changes in the chemical and electrical properties of the ZnO films caused by the oxygen remote plasma treatment, ZnO thin film transistors were fabricated and their electrical properties were investigated. We found that the Ion/Ioff ratio increased from 7.3,,104 to 8.6,,106, the subthreshold swings improved from 1.67 to 0.45,V/decade, and the saturation mobility (sat) decreased from 1.63 to 0.72,cm2/V,s as plasma exposure times were increased. [source]


    Passivation study of the amorphous,crystalline silicon interface formed using DC saddle-field glow discharge

    PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 3 2010
    Barzin Bahardoust
    Abstract The DC saddle-field (DCSF) glow discharge method was used to deposit intrinsic a-Si:H onto c-Si to passivate the c-Si surface. The effective minority carrier lifetime in the heterostructures as a function of the excess minority carrier density in the c-Si wafers was measured. The results were then analyzed in the context of recombination associated with interface defect states using three known recombination models. The defect density and the charge density at the interface are inferred. In addition subsequent annealing of the samples was studied. It is shown that for our intrinsic a-Si:H samples improvements in surface passivation are directly correlated with the reduction of interface defects and not the reduction of minority carrier concentration at the interface due to electric field. We have achieved excellent surface passivation with effective carrier lifetime >4,ms for an intrinsic a-Si:H sample deposited at a process temperature of 200,C and thickness of about 30,nm. It is also demonstrated that subsequent annealing, at 240,C, of the samples which were prepared at process temperatures <240,C greatly increases the effective lifetime. [source]


    Thermoelectric properties of rapid hot pressed polycrystalline Ag1,xPb18SbTe20 synthesized from doping PbTe nanocrystals

    PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 1 2010
    Xingliang Xin
    Abstract Polycrystalline thermoelectric (TE) materials of n-type and with compositions of Ag1,xPb18SbTe20 (x,=,0, 0.1, 0.2) were prepared by rapid hot pressing from alloy powders, which were obtained by ball milling crystalline ingots. The ingots were synthesized from PbTe nanoparticles, made by solvothermal reactions, and Ag, Sb and Te powders via vacuum-sealed melting in quartz ampoules. Through rapid hot pressing at 748,K for 15,min under 80,MPa, the polycrystalline samples possessed 95% relative densities with the average grain size of 5,m. The electrical resistivity, Seebeck coefficient and thermal conductivity of the Ag1,xPb18SbTe20 (x,=,0, 0.1, 0.2) samples were measured in the range from room temperature (RT) to 673,K. The thermal conductivity was dramatically decreased, caused by scattering of phonons from grain boundaries and interfaces. By optimizing the values of carrier concentration and carrier transference, the Ag1,xPb18SbTe20 (x,=,0.2) sample achieved a maximum ZT value of 1.019 at 673,K. [source]


    Theoretical analysis of optical gain in PbSe/Pb1,xSrxSe quantum well lasers

    PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 11 2009
    Y. H. Sun
    Abstract In this article, theoretical calculation of optical gain has been performed for IV,VI lead salt PbSe/Pb1,xSrxSe quantum well lasers emitting at about 4,6,m by using an analytic gain expression. The reduced density of states and interband transition matrix elements used in the calculation were derived in the framework of the kp model. Peak optical gain as a function of carrier concentration and radiative current density was calculated. The material parameters and laser structures that affect device performance were analyzed in details. [source]


    Schottky contacts to hydrogen doped ZnO

    PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2008
    R. Schifano
    Abstract High resistivity (,1 k, cm) hydrothermally grown single crystal ZnO wafers were modified by hydrogen implantation. The implantation has been performed with multiple energies in order to form a box-like profile with a depth of 4 ,m and two different concentrations of 8 1017 H/cm3 and 1.5 1018 H/ cm3. A subsequent annealing at 200 C for 30 min in N2 resulted in the formation of a highly conductive layer. Pd con- tacts deposited on the implanted side showed rectifying behaviour by up to three orders of magnitude. However by capacitance vs. voltage (C ,V) technique a carrier concentration significantly lower than the one expected according to the implanted H content was measured suggesting the presence of a high density of compensating centers and/or an incomplete activation of H as a donor. ( 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Effect of oxygen partial pressure on optical and electrical properties of co-sputtered amorphous zinc indium tin oxide thin films

    PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 7 2008
    K. J. Saji
    Abstract Transparent thin films of amorphous zinc indium tin oxide were prepared at room temperature by co-sputtering of zinc oxide and indium tin oxide. Effect of oxygen partial pressure on the optical and electrical properties of amorphous zinc indium tin oxide thin films were investigated. Conductivity, carrier concentration and Hall mobility showed strong dependence on the oxygen partial pressure and these parameters decreased with the increase of oxygen pressure. The effect of subgap states caused a sharp difference in measured optical band gap values between the films deposited with and without oxygen partial pressure. Carrier transport studies were carried out by temperature dependent conductivity measurements. At low electron density, the conductivity showed thermally activated behaviour and at higher carrier concentrations it changed to almost degenerate band conduction. ( 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Effect of annealing temperature on the electrical transport properties of CaRuO3,, thin films directly deposited on the Si substrate

    PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 7 2007
    Hanjong Paik
    Abstract We investigate the effect of annealing temperature on the preferentially (110)-oriented CaRuO3,, (CRO) thin films directly prepared on Si(100) substrate by rf magnetron sputtering. Crystalline quality and electrical transport properties of the CRO thin films were modified by post-annealing treatment. It was obvious that 700 C post-annealing brought about excellent metallic characteristics with the elevation of carrier concentration and mobility. From this result, we suggested that enhanced (110) orientation, and the ratio of chemical composition Ru4+/Ca2+ ion were responsible for the transport properties of CRO thin film. ( 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Dynamics of spin interactions in diluted magnetic semiconductor heterostructures

    PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 1 2007
    *Article first published online: 19 DEC 200, D. R. Yakovlev
    Abstract This paper gives an overview of the recent studies of spin dynamics in diluted magnetic semiconductor heterostructures based on (Zn,Mn)Se and (Cd,Mn)Te. The spin dynamics is controlled by energy and spin transfer between systems of magnetic ions, lattice (phonon system) and free carriers. Spin,lattice relaxation time of the Mn spin system is a very strong function of the Mn content, it decreases by five orders of magnitude when the Mn content changes from 0.4 to 11%. Additionally this time can be tuned by the varying free carrier concentration and by the growth of heteromagnetic structures with inhomogeneous profile of Mn ions. ( 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Effects of oxygen ion implantation in spray-pyrolyzed ZnO thin films

    PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 5 2006
    K. P. Vijayakumar
    Abstract ZnO thin films, prepared using the chemical spray pyrolysis technique, were implanted using 100 keV O+ ions. Both pristine and ion-implanted samples were characterized using X-ray diffraction, optical absorption, electrical resistivity measurements, thermally stimulated current measurements and photoluminescence. Samples retained their crystallinity even after irradiation at a fluence of ,1015 ions/cm2. However, at a still higher fluence of 2 1016 ions/cm2, the films became totally amorphous. The optical absorption edge remained unaffected by implantation and optical absorption spectra indicated two levels at 460 and 510 nm. These were attributed to defect levels corresponding to zinc vacancies (VZn) and oxygen antisites (OZn), respectively. Pristine samples had a broad photoluminescence emission centred at 517 nm, which was depleted on implantation. In the case of implanted samples, two additional emissions appeared at 425 and 590 nm. These levels were identified as due to zinc vacancies (VZn) and oxygen vacancies (VO), respectively. The electrical resistivity of implanted samples was much higher than that of pristine, while photosensitivity decreased to a very low value on implantation. This can be utilized in semiconductor device technology for interdevice isolation. Hall measurements showed a marked decrease in mobility due to ion implantation, while carrier concentration slightly increased. ( 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Recombination processes with and without momentum conservation in degenerate InN

    PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 1 2006
    E. Valcheva
    Abstract We report on a theoretical approach in which the two cases of recombination with and without momentum conservation in optically excited high carrier concentration InN are considered. The calculations are used to analyze emission spectra of n-type InN layers of electron concentrations from 7.7 1017 to 1.4 1019 cm,3 studied in the temperature range between 9 and 100 K. The spectra peak near 0.7 eV and the applicability of the two approaches with increasing carrier concentration is estimated. Different transition mechanisms are considered in order to properly account for the observed features in the spectra. Recombination processes involving acceptor- and donor-like localized states are discussed. ( 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Influence of NO2 molecule adsorption on free charge carriers and spin centers in porous silicon

    PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2005
    E. A. Konstantinova
    Abstract The effect of nitrogen dioxide (NO2) adsorption on free charge carriers and spin centers in porous silicon has been studied by FTIR and ESR spectroscopy. The silicon dangling bond (Pb1 -center) density rises with increasing NO2 pressure (P) while free charge carrier concentration depends on P nonmonotonically. The experimental results are explained by a microscopic model taking into account both the formation of P,(NO2), donor,acceptor pairs and NO2 -induced oxidation of Si nanocrystal surfaces. ( 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Study of the electrical conductivity and thermoelectric power of In2Te5 single crystals

    PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 3 2003
    M. M. Nassary
    Abstract In the present study, single crystals of defect semiconductor In2Te5 were grown by the Bridgman technique. An investigation was made on the Hall effect, electrical conductivity and thermoelectric power of In2Te5 monocrystal in the temperature ranging from 200 to 500 K. The investigated samples were P-type conducting. The Hall coefficient yields a room-temperature carrier concentration of (7.7 109 cm,3). The bandgap was found to be (,Eg = 0.993 eV). Hence, a combination of the electrical conductivity and Hall effect measurements enable us to study the influence of temperature on the Hall mobility (,) and to discuss the scattering mechanism of the charge carriers, also the present investigation involves thermoelectric power measurements of In2Te5 single crystal: these measurements enable us to determine many physical parameters such as carriers mobilities, effective masses of free charge carriers (mp*, mn*, diffusion coefficients (Dp, Dn) and diffusion lengths as well as the relaxation time (,p, ,n). ( 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Photoconductivity of Ga doped polycrystalline ZnO films grown by reactive plasma deposition

    PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 5 2007
    Seiichi Kishimoto
    Abstract Photoconductivity and photo-absorption of polycrystalline Ga-doped ZnO (GZO) thin films with film thickness of 200 nm have evaluated compared with undoped ZnO films. The GZO and undoped ZnO thin films were deposited on alkali-free glass substrate at 200 C by a reactive plasma deposition with DC arc discharge technique under an oxygen gas flow rate from 0 to 30 sccm. Undoped ZnO films with carrier concentration of 2.50 1018 and 7.96 1018 cm,3 have exciton absorption at about 3.28 eV. For these films, the photoconductivity peak is agreement with the photon-energy of exciton absorption in the optical-absorption. The optical band edge of undoped ZnO films estimated from the optical-absorption shows a shift to higher energy with increasing the carrier concentration. The increase of oxygen gas flow rate led to the resistivity change of GZO films from 2.15 10,4 to 4.54 10,3 , cm, corresponding to the carrier concentration change from 1.39 1021 to 1.05 1020 cm,3. The photoconductivity of GZO film is larger than that of undoped ZnO film. The peak energy of photoconductivity spectra of GZO films are seen to little shift to higher energy with increasing the carrier concentration. The GZO film exhibited the larger photoconductivity at the wavelength, ranging widely less than 380 nm. GZO film with carrier concentration more than 1 1021 cm,3 indicated much larger photoconductivity. ( 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Unintentionally doped InN grown onto an atomically flat AlN intermediate layer using plasma-assisted molecular beam epitaxy

    PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 7 2006
    K. R. Wang
    Abstract Unintentionally doped InN has been grown onto an atomically flat AlN intermediate layer on top of the Si(111) substrate using plasma-assisted molecular beam epitaxy (PA-MBE). Though there are lots of micrometer-size indium droplets randomly distributed on the top of the surface, the highest electron mobility of this InN thin film measured at room temperature by van der Pauw method is still higher than 1000 cm2/V s with a carrier concentration of 5,8.9 1018 cm,3. A symmetrical X-ray rocking curve is measured and the full-width-at-half-maximum (FWHM) of this sample is 1089 arcsec. In the meantime, the threading dislocation (TD) density of this material is estimated to around 9.8 108 cm,2 , 7.5 109 cm,2 depending on the probing regions that are studied by the etching technique and field-emission scanning electron microscopy (FE-SEM). (2 1) in situ reflection high-energy electron diffraction (RHEED) patterns show that this sample is grown under In-rich environment with possible In-terminated surface. From the FE-SEM pictures which were taken from the samples after 10 minutes etching in hydrochloride, the surface morphology shows In-polarity-like patterns that coincide with those procured in RHEED. To select and grow a high-quality laminated AlN as intermediate layer is believed to be the major step in obtaining this high electron mobility InN thin film on Si substrate. ( 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Defect contributions to conductivity in poly(3-hexylthiophene)?

    PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 6 2006
    A. N. Caruso
    Abstract We find evidence for a gradual change in the electronic properties of spin coated poly(3-hexylthiophene) thin films with temperature. The conduction properties appears to be mediated by hopping conduction dominated by a low density of defects states within the highest occupied molecular orbital to lowest unoccupied molecular orbital gap, not by a change in band gap. The photoemission and transport measurements indicate a loss of charge mobility or carrier concentration occurs with decreasing temperature, while the molecular configuration (through chain conjugation) also changes with temperature. The defects states identified by photoemission (,1.7 eV) as well as others contributing to the transport properties are believed to be very heterogeneous along the polymer backbone. ( 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Manifestation of the equilibrium hole distribution in photoluminescence of n-InN

    PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 4 2005
    A. A. Klochikhin
    Abstract Photoluminescence (PL) of n-InN grown by molecular beam epitaxy with Hall concentrations from 3.6 to 7.3 1017 cm,3 demonstrates dependences on carrier concentration, temperature, and excitation density which give evidences of a fast energy relaxation rate of photoholes and their equilibrium distribution over localized states. The structure of the PL spectra observed at 4.2 and 77 K in the energy interval from 0.50 to 0.67 eV indicates that a considerable part of holes is trapped by deep and shallow acceptors before the interband recombi- nation with degenerate electrons occurs. At room temperature, the band-to-band recombination of free holes and electrons dominates in PL. Experimental results on PL and absorption are described by model calculations under the assumptions of a band gap equal to 0.665,0.670 eV at zero temperature and zero carrier concentration and a non-parabolic conduction band with the effective mass at the G -point equal to 0.07 of the free electron mass. ( 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Effective mass of InN estimated by Raman scattering

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7-8 2010
    Jung Gon Kim
    Abstract We have estimated the longitudinal effective mass (m,) of electron in n-type InN films by Raman scattering. The samples were grown by MOVPE (metal organic vapor phase epitaxy) with free carrier concentration of n =6.71018 -9.91018 cm -3 according to Hall measurement. A weak Raman signal observed at ,430 cm -1 at room temperature was sharpened and shifted to higher frequency toward the A1(TO)-phonon mode at 447 cm -1 with increasing n. This mode was assigned to the lower branch (L - ) of the longitudinal-optic-phonon-plasmon-coupled (LOPC) mode. The line shape was carefully analyzed by a semi-classical line-shape fitting analysis assuming deformation potential and electro-optic coupling mechanisms for the light scattering process. A line-shape fitting analysis was conducted by adjusting three major parameters; electron density, effective mass and plasmon damping rate. The analysis well reproduced values of electron density and mobility deduced by Hall measurement. Electron effective mass of m,*/m0 = 0.05 (0.01) was also obtained as the best-fit parameter. The result agrees well with previous data obtained by other optical methods. ( 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]