Showing papers on "Photoconductivity published in 1976"
TL;DR: In this article, an energy band model of amorphous GexSe1-x films has been proposed for consistent explanations of experimental data, and measurements of the photoconductivity and the absorption spectra have been made at room temperature.
Abstract: Measurements of electrical and optical properties have been made on GexSe1-x amorphous thin films of about 1 µm thickness. From the experiment of electrical conductivity at various temperatures, two processes of the d.c. conductivity in GexSe1-x films are observed in plots of ln σ against 1/T. The thermoelectric power exhibits a maximum value of p-type conduction at pure Se and a change of the sign from positive to negative at 0.4
165 citations
TL;DR: The photovoltaic properties of Schottky barrier solar cells made from thin films (100-1000 A) of the organic dye hydroxy squarylium have been studied as discussed by the authors.
Abstract: The photovoltaic properties of Schottky barrier solar cells made from thin films (100–1000 A) of the organic dye hydroxy squarylium have been studied. Amorphous and polycrystalline films, prepared by evaporation and solution casting, have strong absorption over the entire visible spectrum. The highest power conversion efficiency measured under AMO white light was 0.1% (0.14 mW/cm2 input intensity); this decreased to 0.02% at 135 mW/cm2. The decrease in η with intensity is characteristic of organic materials, but is usually much more pronounced. For 8500‐A monochromatic light the quantum efficiency was as high as 2.3% and the conversion efficiency was 0.2% (1 mW/cm2).
157 citations
TL;DR: The photoelectronic properties of high resistivity n-type GaAs:: Cr are quite similar to those of high-resistivity n−type O-GaAs described in the preceding paper as discussed by the authors.
Abstract: The photoelectronic properties of high‐resistivity n‐type GaAs : Cr are quite similar to those of high‐resistivity n‐type GaAs : O described in the preceding paper. In the low‐temperature region, intrinsic photoconductivity is n type, increases exponentially with 1/T, and can be consistently described by a simple one‐level Shockley‐Read recombination model with a level lying 0.66 eV below the conduction band and a density that is remarkably constant over a variety of different materials. Two levels characteristic of the Cr doping lie at 0.86 eV below the conduction band and at 0.9 eV above the valence band. Low‐frequency photocurrent oscillations are associated with levels at 0.86 and 1.25 eV below the conduction band. The extrinsic photoconductivity at 0.86 eV is produced via two steps: (i) electrons are photoexcited from the ground state to the excited state of Cr+2 (d4) center, and (ii) they are then thermally excited to the conduction band.
136 citations
TL;DR: In this article, the authors used photoconductivity produced by picosecond optical pulses in silicon to switch electrical signals as large as 15 kV and used it to drive a traveling wave Pockel's cell for efficient optical switching with a measured rise time of approximately 25 psec.
Abstract: Photoconductivity produced by picosecond optical pulses in silicon has been used to switch electrical signals as large as 15 kV The signals have been used to drive a traveling‐wave Pockel’s cell for efficient optical switching with a measured rise time of approximately 25 psec
115 citations
TL;DR: In this article, the acceptor ionization energy was determined to be about 14 meV by measurement of carrier freeze out in Hg0.6Cd0.4Te.
Abstract: Electrical transport measurements have been made on p‐type Hg1−xCdxTe with carrier concentrations ranging from 4×1015 to 1×1017 cm−3 and with x in the range 0.26–0.6. The acceptor ionization energy was determined to be about 14 meV by measurement of carrier freeze out in Hg0.6Cd0.4Te. Far‐infrared photoconductivity and transmittance measurements in Hg0.6Cd0.4Te were used to verify this ionization energy of the acceptor. Calculations of both the ionized‐impurity‐scattering‐limited mobility and the Hall coefficient as functions of temperature indicate that the p‐type Hg1−xCdxTe crystals are compensated.
104 citations
TL;DR: In this paper, the same centers are responsible for the recombination in the diode and in pure silicon, that only the recombinations in the space charge region of the junction is spin-dependent and that the effect in this region is very large.
90 citations
TL;DR: In this paper, the presence of three impurity levels taking part in the photoconductivity process is attributed to a sensitization centre, which acts as a competitive recombination level, and an exponential distribution of electron traps is revealed both by pulsed photoconductivities and by thermocurrent analysis.
Abstract: Photoconductivity, quenching, thermally stimulated current and decay characteristics are studied in ZnIn2S4 single crystals Evidence is obtained for the presence of three impurity levels taking part in the photoconductivity process Optical quenching is attributed to a sensitization centre, which acts as a competitive recombination level An exponential distribution of electron traps is revealed both by pulsed photoconductivity and by thermocurrent analysis The two experimental techniques accordingly provide the value of 70 meV/decade for the trap distribution Some aspects of the nature of the impurity centres are examined
61 citations
TL;DR: In this paper, the authors proposed a new type of far-infrared detector with promising applications for heterodyne detection at wavelengths on the order of 300 μm, which can be used to excite these electrons into the conduction band, giving a photoconductive signal.
Abstract: Shallow donor impurities in silicon at low temperatures are able to bind two electrons, forming negative donor ions, analogous to atomic H− ions. The second electron has a binding energy of only a few meV. Far‐infrared radiation can be used to excite these electrons into the conduction band, giving a photoconductive signal. This mechanism is the basis of a new type of far‐infrared detector, with promising applications for heterodyne detection at wavelengths on the order of 300 μm. The nature of the negative donor ion is discussed, in part from the effective mass analogy with H− atomic ions, and also with H−2 molecular ions. The theory of how this detector will perform as a function of such variables as bias voltage, background intensity, signal level, and signal speed has been examined. Response speeds on the order of 1 nsec are expected, for operation at temperatures ?2 K, with bias voltage as high as 100 V/cm. With unfiltered 300‐K background radiation, the NEP is estimated to be on the order of 10−11 W...
61 citations
TL;DR: In this article, phototransport measurements on chlorine-doped Cd1−xZnxTe crystals with 0.35% Zn content showed a persistent impurity photoconductivity below 140°K.
Abstract: Phototransport measurements on chlorine‐doped Cd1−xZnxTe crystals with 0⩽x⩽0.35 show a persistent impurity photoconductivity below 140 °K. The thermal activation energy of the defect center responsible for both the dark carriers and photocarriers increases from −0.045 eV for x=0 to +0.27 eV for x=0.25 (negative implies above the conduction‐band edge), resulting in a decrease of the dark free‐carrier density with increasing Zn content. This permits an increasing light‐to‐dark‐conductivity ratio with increasing Zn content, reaching 2.5×105 for x=0.25. The increase of the mobility under photoexcitation indicates the center to be a double acceptor. Thermal emission rate, photoconductivity decay, and optical cross‐section measurements are also reported.
57 citations
TL;DR: In this paper, it was shown that the reduced transmission at high intensities is primarily due to the electrons and holes generated by two-photon absorption and not directly due to two-phase absorption process.
Abstract: Transmission and photoconductivity measurements, both as a function of intensity and time have been made at room temperature on indium antimonide using CO2 lasers and on germanium using a hydrogen fluoride laser. In both cases it is shown that the reduced transmission at high intensities is primarily due to the electrons and holes generated by two-photon absorption and not directly due to the two-photon absorption process. Previous work on both materials must therefore be reinterpreted.
TL;DR: In this paper, the authors investigated the energy gap of the second indirect transition Γ25' → L1 of silicon and reported a 2.06 eV energy gap, which differs from that reported by Forman et al.
TL;DR: In this article, the minimum prompt photoconductivity induced by pulses of x rays, gamma rays, and energetic electrons in various amorphous and disordered insulating organic and inorganic materials is predicted on the basis of data for the scattering of hot electrons in solids and the band gap for insulators.
Abstract: The minimum prompt photoconductivity induced by pulses of x rays, gamma rays, and energetic electrons in various amorphous and disordered insulating organic and inorganic materials is predicted on the basis of data for the scattering of hot electrons in solids and the band gap for insulators. For total doses of 3 × 104 to 30 × 104 rad or greater, the minimum prompt photoconductivity is predicted to be linear with dose rate, ?, and is given by ?(?-1cm-1)=5×10-19?0?/Eg2, where ?0 is the density (g/cm3) and Eg is the optical band gap (eV). This formula agrees well with data for a variety of plastics, mica, and borosilicate glass under widely different irradiation conditions. The formula considerably underestimates absolute values of prompt conductivities observed for Al2O3, MgO, and certain plastics, because the model does not hold for ordered materials.
TL;DR: In this article, the photoconductivity measurements as a function of excitation intensity and temperature are analyzed for 20 amorphous compound semiconductors of V•VI, IV•V, IV'VI, and IV'V•VI types.
Abstract: Photoconductivity measurements as a function of excitation intensity and temperature are analyzed for 20 amorphous compound semiconductors of V‐VI, IV‐V, IV‐VI, and IV‐V‐VI type. Two principal types of photoconductivity are distinguishable; in type I, the photoconductivity exhibits a maximum at a particular temperature and is comparable to or greater than the dark conductivity, whereas in type II, the photoconductivity exhibits no maximum and is much less than the dark conductivity. Indications of localized state energies, densities, and recombination coefficients are obtained by analyzing the photoconductivity data according to the model of Arnoldussen et al. Basic trends, in which the various parameters scale with the optical absorption gap, are discernible for many of the materials. Additional data are supplied on the effects of annealing and crystallization, and photoductivity decay measurements are interpreted to provide indications of the density of localized states near the Fermi level.
TL;DR: In this article, the photoconductivity of poly-2,4-hexadiyne-1,6-diol bis(p -toluene sulfonate) is investigated.
TL;DR: In this article, the spectral response of photovoltage is discussed in terms of two photovolastic processes at the SnO 2 ǫCdS and CdSIn interfaces.
TL;DR: In this paper, the absorption of light, luminescence, spectral distribution of the photoconductivity and the drift mobility of charge carriers in a new organic semiconductor poly-N-epoxypropylcarbazole have been investigated.
TL;DR: In this paper, the properties of phosphors under low voltage cathode ray excitation were investigated, and it was shown that photoconductivity is also an important factor in addition to dark conductivity.
Patent•
02 Feb 1976TL;DR: In this paper, an accumulation mode charge injection device utilizing the extrinsic photoconductivity of a doped semiconductor material to sense infrared radiation is presented. But the device is operated at cryostatic temperatures to preclude thermal ionization of the impurity sites and majority carriers are produced by IR photons interacting with these sites.
Abstract: The present invention relates to an accumulation mode charge injection device utilizing the extrinsic photoconductivity of a doped semiconductor material to sense infrared radiation. The device is operated at cryostatic temperatures to preclude thermal ionization of the impurity sites and majority carriers are produced by IR photons interacting with these sites. The device utilizes a metal-oxide-semiconductor structure to accumulate the IR photon induced majority carriers at the semiconductor oxide interface under a first bias condition. When the bias is reversed the accumulated charges are injected into an output electrode. The sensor may be used singly or in arrays of similar sensors.
TL;DR: In this paper, the mechanism of carrier generation in sublimated rubrene films in the course of their oxidation is investigated, and the existence of an efficient channel of generation of triplet rubrene excitons associated with the deactivation of excited triplet complexes of rubrene with transannular peroxide molecules MO2 is shown.
Abstract: The mechanism of carrier generation in sublimated rubrene films in the course of their oxidation is investigated. The technique of the simultaneous measurement of photoconductivity and fluorescence of the samples and their variation in magnetic fields up to 3 kOe is employed. The excited states whose deactivation leads to both, fluorescence and carrier generation in unoxidized films are found to be rubrene singlet excited molecules 1M1 and in films exposed to air, excited complexes of 1M1 with O2 molecules and with transannular rubrene peroxide molecules MO2. The probability of carrier generation in the interaction of 1N1 with O2 is higher than with MO2. The existence is shown of an efficient channel of generation of triplet rubrene excitons, associated with the deactivation of excited triplet complexes of rubrene with MO2. The influence is investigated of variations in the crystalline structure of films on the behaviour of photoconductivity.
[Russian Text Ignored].
TL;DR: In this article, photoinduced changes of refractive index (PCI) in nonpolar PLZT is attributed to photoconductivity at the wavelength λ = 488 nm.
Abstract: Photoinduced changes of refractive index (PCI) in nonpolar PLZT is attributed to photoconductivity at the wavelength λ = 488 nm. Optical measurement of PCI profiles suggests that average photocarrier drift length is 〈l〉 ≃ 0.8 μm and they are positively charged.
TL;DR: In this article, the main peculiarities of light-induced long-time conductivity relaxations (persistent conductivity) are simulated on a structure representing the GaAs epitaxial film on the semi-insulating substrate of the same material.
Abstract: The main peculiarities of light-induced long-time conductivity relaxations (persistent conductivity) are simulated on a structure representing the GaAs epitaxial film on the semi-insulating substrate of the same material. The similarity of the photoconductivity characteristic features in the above-mentioned system and in naturally-inhomogeneous semiconductor is proved both theoretically and experimentally.
[Russian Text Ignored]
TL;DR: In this article, the angular dependence of the Zeeman splitting of the sharp lines demonstrates that the normal 90° symmetry of the 100 surface is lifted for devices with thin metal gates due to the presence of strong unixial stress component.
TL;DR: In this paper, it was shown that a blocking contact on As2Se3 becomes injecting upon trapping photogenerated electrons, and the steady-state photoconductivity of the photocurrent was investigated in detail.
Abstract: It is shown that a blocking contact on a‐As2Se3 becomes injecting upon trapping photogenerated electrons. The blocking contact consists of a thin organic insulator layer between a semitransparent gold anode and the photoconductor. Gains exceeding unity have been observed. The dynamics of the blocking‐to‐injecting contact transition have been investigated, and its process has been interpreted in terms of thermally assisted tunneling. This effect, in which one observes a blocking contact and an injecting contact in one sample, allows one to study both the primary and the conduction photocurrents in a sequential manner in a‐As2Se3. Applying this technique, the steady‐state photoconductivity of a‐As2Se3 has also been investigated in detail. The results of the steady‐state photocurrent measurements are examined in terms of the classical photoconductivity theory.