Spectral Distribution Of Photoconductivity Research Articles

PHOTOELECTRICAL PROPERTIES OF p-Si/Cd1-xZnxS(Se)1-ySe(Te)y HETEROJUNCTIONS

In this paper the photoelectrical properties of p-Si/Cd1-xZnxS(Se)1-ySe(Te)y type thin film heterojunctions in a wide range of wavelengths (300 - 1400 nm) were characterized depending on the quantitative composition (0≤x≤1 and 0≤y≤1) of Cd1-xZnxS(Se)1-ySe(Te)y type films, electrochemical deposition potential, mode and medium of heat treatment (HT). In order to clarify the effect of these factors on the photoelectric properties and basic parameters of heterojunctions with different composition, the spectral distribution of photoconductivity, volt-ampere characteristics (I-U characteristics), amper-light characteristics were studied.

Photovoltaic Properties of MnGaInS4 Single Crystals

The spectral distribution of photoconductivity and the temperature dependence of photocurrent in MnGaInS4 single crystals have been investigated. Photoconductivity spectra demonstrate both intrinsic and impurity conductivity. In the case of manganese deficiency in crystals, an acceptor-type defect is seen in the wavelength range of 0.64–0.76 μm. The temperature dependence of the MnGaInS4 single crystal bandgap is due to exciton–phonon interaction. In the temperature interval studied, photocurrent rises because of thermal depletion of trapping levels. The activation energy of trapping levels has been calculated.

Фотоэлектрические свойства монокристаллов MnGaInS-=SUB=-4-=/SUB=-

The spectral distribution of photoconductivity and the temperature dependence of the photocurrent of monocrystals MnGaInS4 are studied. The intrinsic and extrinsic photoconductivities are revealed in the spectrum of photoconductivity. The wavelength range of 0.640–0.760 μm is shown when manganese deficiency in crystals appears and is due to an acceptor defect. The temperature dependence of the band gap in the monocrystals MnGaInS4 is related to the electron – phonon interaction. In the studied temperatures, increase in the photocurrent is associated with the thermal depletion of the attachment levels. The activation energy of the attachment levels is estimated.

Photoelectric Properties of Crystalline and Glassy PbGeS<sub>3</sub>

The integrated investigations of the stationary characteristics of photoconductivity (the spectral distribution of photoconductivity (PC), luminous-ampere characteristics (LAC), temperature dependences of dark photoconductivity) and the thermostimulated current (TSC) for crystalline and glassy lead thiogermanate (PbGeS3) were performed. It was determined, as a function of crystals growing rate, there are one or two impurity maxima except for the native one in photoconductivity spectra. For the glassy lead thiogermanate in the range of wave lengths of 0.4 - 1.0 μm in PC spectra was revealed the hysteresis at the change of direction wave lengths sweep of incident light, conditioned by the phenomenon of induced impurity conductivity. The activation of PC, caused by thermal emptying of attachment levels, was observed on the temperature dependences of photoconductivity.

Фотоэлектрические свойства кристаллического и стеклообразного SnGeS3

The integrated investigations of the stationary characteristics of photoconductivi-ty (the spectral distribution of photoconductivity (PC)), luminous-ampere character-istics (LAC), temperature dependences of dark photoconductivity) and the thermost-imulated current (TSC) for crystalline and glassy lead thiogermanate (PbGeS3) were performed. It was determined, as a function of crystals growing rate, there are one or two impurity maxima except for the native one in photoconductivity spectra. For the glassy lead thiogermanate in the range of wave lengths of 0,4-1,0 μm in PC spectra was revealed the hysteresis at the change of direction wave lengths sweep of inci-dent light, conditioned by the phenomenon of induced impurity conductivity. The activation of PC, caused by thermal emptying of attachment levels, was observed on the temperature dependences of photoconductivity. Key words: Lead thiogermanate; Photoconductivity; Crystal; Glass.

Spectral distribution of photocurrent in poly(6- tert-butyl-3-methyl-3,4-dihydro-2 H-1,3-benzoxazine)

The spectral distribution of photoconductivity in poly(6- tert-butyl-3-methyl-3,4-dihydro-2 H-1,3-benzoxazine) was studied in the sandwich configuration with indium tin oxide and silver electrodes. The photocurrent was found to originate mainly from the bulk dissociation of excitons with lesser contribution from electrode-mediated exciton dissociation. The molecule was fluorescent, but in the presence of the electron acceptor molecule 2,4,6-trinitrophenol (TNP), the intensity was reduced. The reduction in fluorescence intensity corresponded to an increase in photocurrent. The molecule showed photoconductivity in the visible without any sensitizers, which makes it suitable for stable photorefractive composites.

X-ray diffraction study of the AgCd 2−xMn xGaS 4 semiconductor alloys and their electrical, optical, and photoelectrical properties

The AgCd 2− x Mn x GaS 4 alloys were investigated by powder X-ray diffraction. The AgCd 2− x Mn x GaS 4 solid solutions exist in the range of 0 ⩽ x ⩽ 1.2 4 . The refinement of the AgCd 0.8Mn 1.2GaS 4 crystal structure (Pmn2 1 space group, a = 0.8 0 7 6 8 ( 3 ) nm , b = 0.6 8 1 0 5 ( 2 ) nm , c = 0.6 5 2 0 3 ( 2 ) nm , V = 0.3 5 8 6 6 ( 4 ) nm 3 ) has proved the isovalent substitution of Cd with Mn. The band gap energy of the solid solutions has been estimated from the intrinsic absorption edge at 300 K. Within the solid solutions range, the band gap increases from 2.15 eV for the AgCd 2GaS 4 composition to 2.4 eV for the AgCd 0.8Mn 1.2GaS 4 composition. The spectral distribution of photoconductivity has been investigated for different compositions. The AgCd 2− x Mn x GaS 4 alloys with x⩽0.30 exhibit the highest photosensitivity. The strong photoconductivity in the 600–610 nm region is attributed to the presence of cadmium vacancies or cadmium-containing complexes in the crystal structure, which act as the photoactive centers.

Electrical and Photoelectrical Properties of n‐CuInS2 Single Crystals

AbstractThe temperature dependences of free electron density and mobility in n‐CuInS2 single crystals have been determined from the Hall effect measurements. The ionization energy of donors and their densities have been estimated. The results of measurements show that the crystals are strongly compensated. The spectral distribution of photoconductivity, the dependence of photoconductivity on excitation intensity, and the photoconductivity decay with time have been measured in the n‐CuInS2 crystals at different temperatures. The results of photo‐conductivity measurements suggest linear recombination of photo‐electrons at weak excitation and quadratic recombination at high excitation intensity. The compensated deep acceptor probably acts as the recombination centre.

Photoconductivity and optical absorption of dimorphite thin films

AbstractOptical absorption and photoconductivity of As4S3 thin films have been studied. The absorption coefficient is shown to be influenced by the technology of film preparation, in particular by growth velocity and substrate temperature. An absorption band with maximum at hv ≈ 1.9 eV has been observed at the absorption edge for films prepared at low growth velocities. Simultaneously a maximum appears in the spectral distribution of photoconductivity, the position and width of which also depend on the technology of film preparation. The results are explained with taking into consideration the inhomogeneity of films containing α and β dimorphites revealed by X‐ray diffraction studies.

Photoconductivity studies of gallium sesquisulphide single crystals

Photoconductivity studies were carried out on single crystals prepared from melt. We studied the effect of light intensity, applied voltage, and ambient temperature on both the spectral distribution of photoconductivity and the lifetime of carriers. We found that the mode of the spectral characteristics was practically independent of the light intensity and applied bias voltage, but shifted to higher values of the photocurrent with increase light intensity and applied bias voltage. It was also noticed that the photocurrent decreases with the increase of temperature up to 200 K and increases above this temperature. The () behaviour was in agreement with behaviour described by the Varshni equation; its constant was found to be , and the temperature coefficient . It was shown that the lifetime decreases with an increase of light intensity and applied voltage, increases with a decrease in temperature and, below 200 K, the lifetime decreases with an increase in temperature.

Growth and characterization of PbS deposited on ferroelectric ceramics

The growth and properties of PbS thin films, chemically deposited on bulk lead titano-zirconate ceramics, are investigated. Scanning electron microscopy photographs reveal that the medium size of crystallites is much larger for PbS films grown on poled ferroelectric substrates than for the films grown onto glass or onto unpoled ferroelectric substrates. In the first case the medium size of crystallites is about 1–1.5 μm while in the second case it is less than 0.3 μm. Spectral distribution of photoconductivity and thermally stimulated currents (TSC) measurements were performed on all samples. Experimental results indicate that the properties of the PbS films can vary, depending on the substrate nature and in the case of poled ferroelectric substrates, on the polarity. The photoconductive signal is usually larger, the dark resistivity is smaller, and the TSC current value is higher for PbS films deposited on the positive face of the ferroelectric substrate than for those deposited on the negative face.

Effect of cobalt impurities on the electrical and photoelectrical properties of GaS single crystals

Static dark current-voltage characteristics (CVC's), the temperature dependence of electric conductivity [σ( T)], the currents of thermostimulated depolarization (TSD), the spectral distribution of photoconductivity (SDPC) and photoluminescence (PL) have been studied in GaS 〈0.1 at % Co〉 single crystals. The results of complex investigations of CVC's, σ( T) dependences, TSD, the SDPC and PL show that the forbidden gap of GaS 〈0.1 at % Co〉 single crystals exhibits acceptor levels ( E V + 0.26 and E V + 0.63 eV).

Influence of an electric field on the spectral distribution of photoconductivity in thin films of chalcogenide glasses of the system (As 2Se 3) 1− x:(Tl 2Se) x

In this paper are reported the measurements of the effect of an electric field on the photoconductivity activation energy of vitreous As 2Se 3 and its compounds with Tl 2Se, in the thin film form. The electric field decreases the photoconductivity band gap energy of these semiconductors. A shift in the band gap energy of the order of 0.03 eV was noted. The threshold electric field for this shift was found to be composition dependent and seemed to vary inversely as the concentrations of the Tl 2Se molecules. It was the lowest for the semiconductor having the smallest energy gap. Also the magnitude of the shift was the highest for the glass having no concentration of Tl 2Se.

The Effect of γ-Irradiation on Photoelectrical Properties of Sb–GaSe Structures

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Spectral distribution of photoconductivity and lifetime in CdTe at the presence of surface trapping processes

The spectral distribution of steady-state photoconductivity has been studied in p-type CdTe single crystals in the wavelength range 0·6–1 μ. The kinetics of photoconductivity has been measured by the frequency dependence and relaxation of photoconductivity. The relaxation of photoconductivity signals is controlled by two processes of carrier trapping indicating the presence of two energetic levels in the gap. The spectral dependence of effective photoconductivity relaxation time (τeff) passes through a minimum value. The position of τeff min coincides with the position of the photoconductivity maximum at λ = 0·85 μ. An explanation of the experimental data is given on the basis of the localized photoconductivity in the surface space charge region as well as in the bulk photoconductivity.

Anomalies of photoconductivity in ferroelectrics near the phase transition

In the ferroelectric-semiconductor SbSI the spectral distribution of photoconductivity in the region of energies of photons less than the energy gap, and also the persistent conductivity induced by the action of light and electric fields have been studied. The peculiarities of these phenomena near the phase transition are discussed by assuming that a ferroelectric may be considered as an inhomogeneous semiconductor.

Trap distribution and photoconductivity in ZnIn2Se4 and ZnIn2Te4

Spectral distribution of photoconductivity in ZnIn2Se4 and ZnIn2Te4, its response time, and its lux-ampere characteristics were investigated and compared with previous results. The nature of the gap, its depth and thermal dependence were elucidated for both materials. Trap distribution, which explains photocurrent intensity dependence and its decay time, is evaluated. A model for photoconductivity processes consistent with the complete set of experimental results is established.

Studies on Photoconductive Thallous Sulphide Cells

Thallous sulphide layers have been prepared by us by the method of chemical deposition for the first time. With suitable electrode contacts, these cells exhibit photoconducting property in the visible and near infrared regions. The spectral distribution of photoconductivity, the lux-ampere characteristics and the response time of these cells have been obtained. The influence of certain dopants on the photosensitivity and dark conductivity of these cells have been studied and discussed.

Studies on sintered photoconductive layers of antimony trisulphide

Antimony trisulphide was sintered on to glass blanks and their electrical and photoconductive properties such as spectral distribution of photoconductivity, current-voltage characteristics and lux-ampere relationship are presented.

Effect of Self-Purification and Polarity on Surface Photoconductivity of CdS Crystals

It was possible to grow pure CdS crystals, which displayed only the intrinsic photoconduction, by sublimation in which sublimating CdS vapor worked as a trap to remove impurities. CdS crystals without intentionally added impurities thus obtained had a wide range of specific resistivity from 10 to 1013\\varOmega cm. Specimens with surfaces parallel to C-plane about 7×5×1 mm3 in size were sliced off a single crystal boule having various resistivities, of which dark resistivities, spectral distribution of photocurrent and thermally stimulated current were studied on both (0001) and (0001̄) surface. From the results of the measurement of the thermally stimulated current curves, it was found that shallow electron traps were predominant in (0001̄) surface, whereas deep electron traps were predominant in (0001) surface. In the case of dark resistivity and spectral distribution of photoconductivity, the experimental results are shown as a tendency in which the local segregations were more effective on these properties, compared with the influences of polarity on them.