Showing papers on "Doping published in 1980"

Mechanism of Yellow Luminescence in GaN

Abstract: The mechanism of the yellow luminescence in GaN has been studied. The yellow band is observed in microcrystals synthesized from Ga and NH3 by direct reaction, but is not observed in needle-like crystals grown by sublimation-recrystallization. Doping with carbon emphasizes the yellow band. The characteristic excitation band is observed in C-doped GaN. The yellow band is due to a radiative transition from a shallow donor with a depth of 25 meV to a deep acceptor with a depth of 860 meV. The relation between the characteristic excitation band and the emission band is interpreted by the simple configuration coordinate model. The deep acceptor is thought to be a complex consisting of a gallium vacancy and a carbon atom substituted for a nearest neighbour of the gallium sites.

Electrical and optical properties of undoped and antimony‐doped tin oxide films

Abstract: Tin oxide films have been prepared on glass substrates by spray pyrolysis technique. The electrical and optical properties of undoped and antimony‐doped tin oxide films have been studied. The temperature dependence of electron mobility has been analyzed to establish the electron conduction mechanism. Optical properties near the plasma edge have been analyzed using Drude’s theory. The dependence of effective mass on carrier concentration has been explained on the basis of nonparabolicity of the conduction band. The shift in the Fermi energy, calculated on the basis of energy dependent effective mass, is consistent with the measured shift in the absorption edge.

Electrical transport in doped polyacetylene

Abstract: The results of an experimental study of electrical conductivity and thermopower in doped polyacetylene are reported. Included are measurements on both as‐grown and partially oriented films doped with iodine and AsF5; [CH(AsF5)y]xand [CH(I3)y]x, where y covers the full doping range. The data indicate three important concentration regimes; the dilute limit (y<0.001), the transitional region (0.001

Planar-doped barriers in GaAs by molecular beam epitaxy

Abstract: A new majority carrier rectifying device is demonstrated which is made in gallium arsenide by molecular beam epitaxy. It exhibits thermionic transport with positive and negative bias and the barrier height and degree of asymmetry in the I/V characteristic can be continuously varied. The device also shows a constant capacitance with bias.

Principles of photoelectrochemical, solar energy conversion

Abstract: Photoelectrochemical devices for conversion of solar energy into both electrical energy and chemical energy are discussed with emphasis on how the various material properties of the photoactive electrodes influence device efficiency and stability. The similarity between photoelectrochemical cells (PECs) and solid state devices is used to model their behaviour and optimize such parameters as band gap, doping level, minority carrier lifetime, etc. A model is presented which calculates the electron affinity of any semiconductor and allows the prediction of the open circuit voltage of wet photovoltaic cells and optimum biasing forchemical producing cells. The effects of absorbed ions at the semiconductor/electrolyte interface are reviewed. The temperature dependence of the energy levels in the semiconductor and the electrolyte are considered and the implications of these results to operation of PECs at elevated temperature are discussed. The major differences between PECs and solid state devices are the stability considerations. The thermodynamics of this problem is discussed. Other important degradation mechanisms and some solutions to these problems are reviewed. Finally, a prognosis of the future of this field is presented.

Complex free‐carrier profile synthesis by ’’atomic‐plane’’ doping of MBE GaAs

Abstract: Doping solely during periods when growth was suspended has been used to synthesize profiles not easily achieved by conventional doping techniques. Suspension of growth under arsenic stabilized conditions allows Ge doping to produce n‐type complex profiles with reduced autocompensation. At higher temperatures, autocompensation becomes apparent. Under gallium stabilized conditions, heavily autocompensated n‐type layers resulted, consistent with a nonunity incorporation coefficient.

Resistivity‐Dopant Density Relationship for Phosphorus‐Doped Silicon

Abstract: New data for the resistivity‐dopant density relationship for phosphorus‐doped silicon have been obtained for phosphorus densities between 1013 and 1020 cm−3 and temperatures of 296°K (23°C) and 300°K. For dopant densities less than 1018 cm−3, results were calculated from resistivity and junction capacitance‐voltage measurements on processed wafers. For more heavily doped material, data were obtained from Hall effect and resistivity measurements on specimens cut from bulk silicon slices. The results differ by 5–15% from the commonly used Irvin curve, always in the direction of lower dopant density for a given resistivity. For comparison with the electrical measurements, phosphorus densities were also obtained by neutron activation analysis and the photometric technique. The values from these methods were within 10% of the electrical results. Analytical fits were determined for the resistivity‐dopant density product as a function of resistivity and dopant density for temperatures of 23°C and 300°K. Similar fits were obtained for the calculated electron mobility as a function of resistivity and electron density.

Electronic Properties of a Semiconductor Superlattice II. Low Temperature Mobility Perpendicular to the Superlattice

Abstract: Low temperature mobilities parallel to the layers of a heavily doped n-type GaAs–Ga 1- x Al x As superlattice are calculated as a function of carrier concentrations. Assumed scattering mechanisms are Coulomb scattering from donor ions and surface roughness scattering at the interface. The subband structure in the presence of the band bending is calculated by the variational method. The surface roughness scattering is shown to be relatively unimportant and the Coulomb scattering is dominant. The mobility in the modulation doping case becomes nearly one order of magnitude larger than that in the uniform doping case in agreement with recent experiments. The band bending effect is important in the modulation doping case and reduce the mobility at large carrier concentrations. The intersubband scattering greatly reduces the mobility when electrons occupy higher subbands.

Electrical and Structural Properties of Phosphorous-Doped Glow-Discharge Si:F:H and Si:H Films

Abstract: Doping of Si:F:H and Si:H with P has been performed by a glow-discharge technique using PH3/SiF4+H2, PF5/SiF4+H2, PH3/SiH4+H2 and PF5/SiH4+H2 gaseous mixtures, and high conductive films over 100 ?-1 cm-1 have been obtained. It has also been made clear from X-ray diffraction and Raman-scattering measurements that all the P-doped Si:F:H films (P/Si>5?10-4) as well as high conductive Si:H films deposited under high RF power condition are polycrystalline, while Si:H films prepared under low power remain amorphous and their conductivity is less than 10-2 ?-1 cm-1. It is likely that film conductivity amounting to 100 ?-1 cm-1 should be ascribed to its polycrystalline structure.

Silicon molecular beam epitaxy with simultaneous ion implant doping

Abstract: Silicon epitaxial layers have been made with virtually any doping profile by combining molecular beam epitaxial growth with simultaneous ion implant doping. Arsenic ions (As+) accelerated to energies between 400 and 800 eV have shown a high sticking coefficient on the heated silicon surface. Growth conditions have been defined at which epitaxial films with bulk characteristics are obtained.

Charge carrier localization in pure and doped 1T-TaS2

Abstract: We review experimental data on the low-temperature behaviour of pure, and cation-doped 1T-TaS2, This suggests that the transition into the commensurate phase is accompanied by Mott-localization while below helium temperatures, conduction proceeds by variable range hopping in disorder-localized states lying in a region where the Mott-Hubbard subbands slightly overlap. Many properties of doped samples can be understood by assuming that the star-shaped atomic clusters characteristic of pure material are preferentially centred on impurities.

Properties of Zn‐doped VPE‐grown GaN. I. Luminescence data in relation to doping conditions

Abstract: Experimental results on optical and electrical properties of VPE‐grown GaN doped with Zn under various conditions of growth are presented. The incorporation of Zn into GaN was found to be critically dependent on growth conditions. Four different Zn‐related acceptorlike centers A–D were found to occur, with broad radiative emissions peaking at 2.87 (A), 2.6 (B), 2.2 (C), and 1.8 eV (D). Their broad shape was found to be due to a moderate lattice relaxation upon optical transitions. A linear model for phonon coupling was found adequate, with a principal mode resonant with the optical band [h/ω, varying between 74 (A level) and about 84 meV (C level)] and an additional lower‐energy mode, yielding Franck‐Condon shifts for these centers ΔFC,A =0.25±0.03, ΔFC,B=0.25±0.04, ΔFC,C =0.28±0.04 eV, and ΔFC,D=0.28±0.05 eV. Data for electrical compensation related to the occurrence of these different emissions indicate that the A level could be the ZnGa substitutional acceptor, while the more efficiently compensating B...

An application of the Boltzmann transport equation to ion range and damage distributions in multilayered targets

Abstract: A method for the direct calculation of primary ion and recoil range distributions, as well as energy deposition profiles in multilayered targets, is presented. The technique is based on stepwise numerical integration of the Boltzmann transport equation. Range distributions for arsenic, phosphorus, and boron and damage density distributions resulting from antimony and boron implants in silicon are found to compare favorably with other calculations and experimental results. Oxygen recoil fluxes from SiO2 into Si also agree well with experiment. Silicon and nitrogen recoil range distributions resulting from a 400‐keV selenium implantation through 1000 A of Si3N4 on GaAs are calculated and are shown to have a significant effect on doping profiles determined from electrical measurements.

Method of making p-doped silicon films

Abstract: The production of improved photovoltaic solar cells and the like comprising both p and n type deposited silicon film regions is made possible by a process which provides more efficient p-doped silicon films with higher acceptor concentrations. The process utilizes previously known p-dopant metal or boron gaseous materials in unique forms and conditions in a glow discharge silicon preferably hydrogen and fluorine compensated deposition process. Thus, p-dopant metals like aluminum may be used in an elemental evaporated form, rather than in a gaseous compound form heretofore ineffectively used and deposited with the glow discharge deposited silicon on substrates kept at lower temperatures where fluorine and hydrogen compensation is most effective. Preferably boron in a gaseous compound form like diborane and other p-dopant metals in a gaseous form are used uniquely during the glow discharge deposition of silicon by heating the substrate to heretofore believed undesirably higher temperatures, like at least about 450° C. to 800° C. where at least fluorine compensation, if desired, is still effective. The improved devices, such as solar cells, can be manufactured in a continuous process on a web type substrate moved through a plurality of film deposition chambers. Each of the chambers is dedicated to depositing a particular type of film layer (p, i or n) and is isolated from the other chambers.

Self‐Diffusion of Carbon‐14 in High‐Purity and N‐Doped α‐SiC Single Crystals

Abstract: The self-diffusion coefficients of 14C in high-purity, essentially intrinsic and N-doped, n-type α-SiC single crystals were measured at 2123 to 2453 K. The Si14C tracer was chemically bonded by a traveling solvent technique. The Dc* in the doped crystals is smaller than that of the pure materials because of the decreased concentration of the charged donor-type C vacancies in the presence of the donor N species.

Ionic Conductivity and Magnesium Vacancy Mobility in Magnesium Oxide

Abstract: The dc conductivity and ionic transference number of MgO single crystals doped with Al, Fe, and Sc were measured as a function of temperature (1200° to 1600°C) and oxygen pressure (10−1 to 10−13 MPa). Magnesium oxide is a mixed conductor with its ionic component directly proportional to the trivalent solute concentration. The activation energy for ionic conduction equals 202 kj/mol and is independent of the specific trivalent solute used. This behavior results from a defect structure for a single trivalent solute for which the charge balance condition is 2[VMg'] =[IMg], where [VMg”] is the Mg vacancy concentration and [IMg] the trivalent solute concentration. At lower temperatures and high Sc concentrations, effects attributed to Sc ionvacancy association are observed. Ionic conduction results from Mg vacancy motion with a diffusion coefficient of VMg' given by Deduced values of the Mg-ion diffusion coefficient lead to the conclusion that the scatter in the published DMg data largely results from differences in impurity content.

Silicon graphoepitaxy using a strip-heater oven

Abstract: Silicon graphoepitaxy has been achieved using a strip‐heater oven and a sample configuration consisting of a relief grating in a SiO2 substrate, a deposited amorphous silicon film, and a deposited SiO2 overlayer or ’’cap.’’ The resulting films are free of cracks and superior in crystallographic orientation and surface smoothness to graphoepitaxial films produced by laser crystallization. Enhancement‐mode, n‐channel, insulated polysilicon gate field‐effect transistors were fabricated and gave surface mobilities of 400 cm2/V sec at a p doping of 1016 cm−3. A SiO2 cap, either intentionally deposited or produced by laser crystallization in the presence of oxygen, was found to be necessary for Si graphoepitaxy. We attribute this effect to shear stresses produced by the SiO2 cap during crystallization.

Heavy doping effects in p-n-p bipolar transistors

Abstract: This paper presents the heavy doping effects on the injection current characteristics in p-n-p transistors with a heavily doped but thin base region. The results of the present study indicate that 1) at room temperature the hole current injected into heavily doped base is insensitive to the impurity compensation effect, 2) a linear relationship between the base sheet resistance and the collector-current density is observed when the base doping density is under 1 × 1019cm-3. This relationship becomes supralinear as the doping density further increases. As a result, useful current gain exists in thin base transistors even when the base doping is greater than 1 × 1019cm-3. From the collector-current-base sheet-resistance relationship and the base doping profile, the effective intrinsic carrier density as a function of the doping density is evaluated and found to increase 8.7 times over that of pure silicon, when the average doping density is 5 × 1019cm-3(maximum doping density 1 × 1020cm-3). 3) The collector current and the current gain of the transistors become less sensitive to the temperature as the base doping density increases. We had observed a current gain up to 30 at 77 K for transistors with the maximum base doping density in the 1018cm-3range. The transistors with lower base doping suffer much more degradation in current gain when the temperature is lowered to 77 K.

Photoinduced light scattering in cerium-doped barium strontium niobate crystals

Abstract: Photoinduced light scattering was observed in cerium-doped (SrxBa1–x)1–y(Nb2O6)y crystals having the composition x = 0.61, y = 0.4993. It was found that this effect is due to holographic amplification of light scattered by crystal defects. An analysis is made of static and dynamic characteristics of self-amplification of scattered light in the crystals. A theoretical model of the process is constructed assuming that the hologram recording process is of the diffusion type. Theoretical results are compared with the experiment.

Low‐temperature crystallization of doped a‐Si:H alloys

Abstract: Crystallization of phosphorus‐doped a‐Si:H has been initiated at a substrate temperature below 200 °C, under the deposition conditions of a low flow rate of silane and in the presence of an external magnetic field. Along with the crystallization, the doping efficiency of the resulting Si:H films has been remarkably improved. Room‐temperature conductivity as high as 27 Ω−1 cm−1 has been achieved at a doping ratio of NPH3/NSiH4=5.6×10−3 for a specimen deposited at 30 C. Optical emission spectroscopy during the plasma deposition has revealed that a weak emission intensity of the SiH band with respect to hydrogen lines and the absence of emission from the doubly excited states of hydrogen molecules are necessary conditions for the crystallization of doped Si:H films.

Photoluminescence of shallow acceptors in epitaxial AlxGa1−xAs

Abstract: The low‐temperature (2 K) photoluminescence (PL) of AlxGa1−xAs (0

Semiconductor properties of polyacetylene p‐(CH)x : n‐CdS heterojunctions

Abstract: Trans:(CH)x:n‐CdS heterojunctions have been fabricated and used to study the properties of undoped trans‐polyacetylene. The I‐V data show rectifying behavior characteristic of a p‐n junction diode, thus confirming that as‐grown polyacetylene is p type. From C‐V characteristics we infer a residual acceptor concentration in as‐grown films of p‐(CH)x of NA?2×1018 cm−3. Depletion has been studied in the polymer by using CdS of different doping concentrations. Detailed studies of the photovoltaic response at energies below Eg for (CH)x imply the existence of a meta‐stable deep trap in the polymer with energy near the center of the gap. The threshold energy for pumping into this level provides an independent measurement of the energy gap, Eg=1.45 eV.

New rectifying semiconductor structure by molecular beam epitaxy

Abstract: A new unipolar rectifying semiconductor structure is demonstrated. Rectification is produced by an asymmetric potential barrier created by an MBE‐grown sawtooth‐shaped composition wave of AlxGa1−xAs between layers of n‐type GaAs. Single and multiple barriers as well as doped and undoped barriers have been studied and showed rectification. This is the first structure in which rectification has been produced directly by compositional grading.

Method of fabricating MOS field effect transistors

Abstract: A method for making a MOSFET device (20) in a semiconductor body (10) includes the step of forming source and drain contact electrodes (12.1, 12.2) prior to growth of the gate oxide (10.3) and after formation of a high conductivity surface region (10.5). The exposed mutually opposing sidewall edges of each of the contact electrodes (12.1, 12.2) are coated with a sidewall silicon dioxide layer (15.1, 15.2), and the then exposed surface of the semiconductor body (10) between these sidewalls is etched to depth beneath the high conductivity surface region (10.5) in order to separate it into the source and drain regions (10.1, 10.2). Formation of the high conductivity region may be omitted by using Schottky barrier or impurity doped material for the contact electrodes (12.1, 12.2).

Defect structure and oxygen diffusion in undoped and La‐doped polycrystalline barium titanate

Abstract: Oxygen diffusion coefficients in undoped and La‐doped polycrystalline barium titanate were measured at an ambient oxygen pressure of about 40 Torr over the temperature range 770–1430 °C by a solid–gas exchange technique of O18. The undoped material was characterized only by an extrinsic region with a high diffusivity, whereas two types of La‐doped materials displayed an intrinsic region with E?100 kcal/mol in addition to a common extrinsic region of a very low level of diffusivity. New ideas concerning defect equilibria for the doped materials are proposed for the extrinsic and intrinsic region. In addition, the origin of semiconducting behavior characteristic of the doped specimens is interpreted on a basis of new idea.

The effects of ion implantation on the electrical properties of amorphous silicon

Abstract: In this paper we present the results of a systematic study of ion implantation doping in glow-discharge a-Si films using the substitutional impurities, P, As, Sb, Bi, B, Al, Ga, In and Tl and the interstitial impurities Na, K, Rb and Cs. Implantation doping provides the same range of control of the electrical properties as gas phase doping, but at a lower doping efficiency. The compensation of pre-doped specimens by ion implantation has been investigated and found to be feasible and predictable. As an example the characteristics of an implanted a-Si p-n junction are shown. Results with F, Cl, Br and I implantations indicate that the halogens do not act as interstitial acceptors. The effect of implantation damage on electrical properties and its dependence on implantation temperature have been investigated in some detail. Photoconductivity measurements provide a useful approach to the problem and it is concluded that the density of gap states increases with ion dose, even for hot implantations. A ...