Space-charge-limited currents and photoconductive properties of Tl2InGaSe4 layered crystals

The extrinsic electronic parameters of Tl₂InGaSe₄ layered crystals were investigated through measurement of the temperature-dependent dark conductivity, space-charge-limited currents and photoconductivity. Analysis of the dark conductivity reveals the existence of two extrinsic energy levels at 0.40 and 0.51 eV below the conduction band edge, which are dominant above and below 260 K, respectively. Current–voltage characteristics show that the one at 0.51 eV is a trapping energy level with a concentration of (4.8–7.7) × 10¹⁰ cm^?3. Photoconductivity measurements reveal the existence of another energy level located at 0.16 eV. In the studied temperature range, the photocurrent increases with increasing temperature. The dependence of the photoconductivity on the incident light intensity exhibits a linear recombination character near room temperature and a supralinear character as the temperature decreases. The change in recombination mechanism is attributed to an exchange in the behavior of sensitizing and recombination centres.     

Investigation of the electrical and photoelectric properties of manganese-doped gallium arsenide as a material for photoresistive detectors

An investigation was made into the electrical and photoelectric properties of gallium arsenide with an initial electron density 5×10¹⁵–4×10¹⁷ cm^–3 doped with Mn in different thermodynamic diffusion regimes characterized by diffusion temperatures of 900 and 1000°C and arsenic vapor pressure 10^–2 and 10^–3 atm. The ionization energy and defect concentration were determined by a computer analysis of the equilibrium hole density determined from the Hall effect. Centers with ionization energy 0.08–0.10 eV were found, their concentration varying from 2×10¹⁹ to 2×10²⁰ cm^–3 depending on the diffusion temperature and the doping level of the original crystals. Data obtained by investigating the stationary intrinsic photoconductivity were used to determine a hole lifetime of t_p 10^–9 sec. The photoconductivity spectra were investigated in the range 0.5–2 eV at 77°K, and defects with ionization energy E_v + 0.6 eV were found in all samples. The impurity photoconductivity at wavelength 10.6 m was investigated. It was shown that GaAsMn can be used as a material for impurity photoresistors.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 15–19, March, 1981.     

Preparation and basic physical properties of BiTeI single crystals

A modified Bridgman method is described, which makes it possible to prepare homogeneous BiTeI crystals using excess iodine. At room temperature the values of the electrical conductivity of the crystals range around 2000 ^–1 cm^–1, the Hall constant value about 0·09 cm^–3 coul^–1, the Seebeck coefficient about 50 V K^–1. In connection with the assumption of super-stoichiometric iodine content we expect there exist point defects in the crystals, where Te atoms are replaced with I atoms, which gives rise to electric conductivity. On the basis of the temperature dependence of the electron mobility one can suppose a mixed mechanism of the scattering of the free carriers by the acoustic branch of lattice vibrations and by ionized impurities.     

СВОЙСТВА СУРЬМЯНИСТОГО КАДМИЯ, ЛЕГИРОВАННОГО СЕРЕБРОМ, ПРИ НИЗКИХ ТЕМПЕРАТУРАХ

The temperature dependence of the resistivity and the Hall coefficient of Ag doped CdSb single crystals was investigated in the temperature range of 1.5–300°K. It was shown that Ag in CdSb gives shallow acceptor levels with an activation energyE _a =3.5×10^–3 eV. Presence of the admixture band determines the electrical properties of crystals at low temperatures. The energy width of this band is about 10^–3 eV for slightly doped crystals.     

Temperature dependence of the stationary photocurrent in doped sillenite type crystals

The temperature dependence of the photocurrent in doped sillenite-type crystals is investigated in the temperature range 80–300°K. In the region of low temperatures thermally activated photocurrent is observed, while at high temperatures quenching is observed. In a number of specimens the temperature quenching section is absent. The results are explained within the framework of a multilevel recombination model involving slow and fast recombination centers as well as capture levels.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 85–89, June, 1985.     

Some photoelectric properties of p-GaSe monocrystals

The thermostimulated conductivity, static characteristics, and kinetics of photoconductivity in undoped GaSe monocrystals with p-type conductivity are studied over the temperature range 80–350K. Photocurrent as a function of intensity and wavelength of exciting light, and relaxation curves are analyzed. Insignificant temperature and infrared photocurrent extinction was observed. The major parameters of photosensitive centers are determined. It is demonstrated that the experimentally observed principles of photoconductivity in gallium selenide can be explained within the framework of the two-center recombination model, as realized for many wide-zone photoconductors [1–3].Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 66–70, January, 1976.     

Behavior of copper in gallium arsenide with a high concentration of tellurium

The photoelectric properties of gallium arsenide with a high concentration of tellurium (n=2· 10¹⁸ cm^–3) alloyed with copper are investigated for different conditions of diffusion. From the photoconductivity spectrum, the position of the impurity centers with an ionization energy of (E_v+0.6) eV is determined, the concentration of which depends on the vapor pressure of arsenic. The lifetime of the holes in the material studied is determined. Its magnitude and temperature dependence is explained by the presence of certain recombination channels.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 11–15, September, 1979.     

High rate primary ion beam deposition of a-Si:H films

Hydrogenated amorphous silicon films have been prepared by primary ion beam deposition with a new electrodeless rf ion source. The design of the ion source is described. The composition of the a-Si:H films has been determined by Rutherford backscattering, and the photoconductivity by the constant photocurrent method (CPM). The best a-Si:H films show photoconductivities of 5×10^–5 ( cm)^–1. The deposition rates were between 0.7 and 1.2 nm s^–1.     

Effect of IR illumination on photocurrent spectra in CdS crystals

Low-temperature near-band-edge photoconductivity (PC) spectra of CdS crystals were studied as a function of IR illumination intensity in the PC quenching interval. The photocurrent quenching by IR light of the PC response profile has been investigated. An analysis of these relationships permitted establishing a direct connection between the r photoconductivity centers and the near-band-edge structure of the spectrum. The effect of “pinning” of majoritycarrier lifetime on the semiconductor surface has been discovered and interpreted. It is proposed that surface-acceptor states in CdS crystals play the part of surface photoconductivity centers. Fiz. Tverd. Tela (St. Petersburg) 41, 1181–1184 (July 1999)     

Solid solutions of CdSn(As1−xPx)2 and their properties

We have grown single crystals of CdSn(As_1–xP_x)₂ solid solutions over the entire range of x. On the basis of the temperature dependence of the Hall coefficient and the Hall mobility, we conclude that there is a mixed carrier scattering mechanism in all of these solid solutions, over the entire temperature range from 100 to 500 K, involving both impurity ions and thermal lattice phonons. IR absorption and photoconductivity spectra show that the band gap in the solid solutions varies linearly with composition. We conclude that crystals in the range 0.5相似文献   

Temperature dependence of AC-photoconductivity of HgI2 crystal

An ac impedance method has been used to study the electrical properties of an illuminated HgI₂ crystal as a function of temperature [10–350 K] and frequency [1–10₄ Hz]. The complex impedance plane plots enabled us to determine the bulk resistance of the crystal as a function of temperature. Activation energies of [0.08±0.005 eV] and [0.25 ±0.01eV] are then found; they are attributed to acceptor and donor trapping levels, respectively. At temperatures lower than 230 K, a weak temperature dependence of the bulk resistance is observed. This weak dependence is supposed to be due to photoconductivity.     

Photoelectronic and electrical properties of Tl2InGaS4 layered crystals

Tl₂InGaS₄ layered crystals are studied through the dark electrical conductivity, space charge limited current and illumination- and temperature-dependent photoconductivity measurements in the temperature regions of 220-350 K, 300-400 K and 200-350 K, respectively. The space charge limited current measurements revealed the existence of a single discrete trapping level located at 0.44 eV. The dark electrical conductivity showed the existence of two energy levels of 0.32 eV and 0.60 eV being dominant above and below 300 K, respectively. The photoconductivity measurements reflected the existence of two other energy levels located at 0.28 eV and 0.19 eV at high and low temperatures, respectively. The photocurrent is observed to increase with increasing temperature up to a maximum temperature of 330 K. The illumination dependence of photoconductivity is found to exhibit supralinear recombination in all the studied temperature ranges. The change in recombination mechanism is attributed to exchange in the behavior of sensitizing and recombination centers.     

Characteristics of photoconductivity in thallium monosulfide single crystals

This work elucidates the photoconductivity (PC) of thallium monosulfide single crystals. Results are obtained in the 77–300 K temperature range, 1500–4500 V lx excitation intensity, 6–18 V applied voltage, and in the 640–1500 nm wavelength range. Both the ac-photoconductivity (ac-PC) and the spectral distribution of the photocurrent are studied in different values of light intensity, applied voltage and temperature. Dependencies of carrier lifetime on light intensity, applied voltage and temperature are also investigated as a result of the ac-PC measurements. The temperature dependence of the energy gap width was described by studying the dc-photoconductivity (dc-PC).      

Photovoltaic Properties of MnGaInS4 Single Crystals

Technical Physics - The spectral distribution of photoconductivity and the temperature dependence of photocurrent in MnGaInS4 single crystals have been investigated. Photoconductivity spectra...     

Polarization dependence of intersubband absorption and photoconductivity in p-type SiGe quantum wells

We present a detailed study of the polarization dependence of subband absorption and photoconductivity in Si/SiGe quantum wells. For samples with a hole concentration ofp_s2.8×10¹² cm², bothp- ands-polarized absorptions have been observed and transitions to several excited states are clearly identified by comparison with self-consistent Luttinger-Kohn type calculations. The photoconductivity is surprisingly insensitive to the polarization, which indicates the importance of the subsequent transport process on the photocurrent responsitivity.     

Dislocation structure of kcl crystals grown with vibration of the melt

Summary The amplitude at all frequencies was 0.04 mm. Three crystals were grown at each frequency, with seeds of dislocation density D = 6 × 10⁴ cm^–2. Figure 1 shows the frequency dependence of the final D. Each point in Figs. 1 and 2 is the mean from 50 measurements (50 fields of view). At all frequencies except 180 Hz, D was 2–4 times less than that without vibration, while at 100 and 160 Hz it was less by nearly an order of magnitude.The effects of amplitude (0.02 to 0.2 mm) were examined at 100 Hz, the minimum D occurring at 0.1 mm (Fig. 2). At 0.04–0.08 mm, D was less by a factor 3–4 than for crystals grown without vibration, while at 0.1 mm it was less by an order of magnitude, being 2 × 10^–4 cm^–2. The size of the etch pits on crystals grown at amplitudes up to 0.1 mm did not differ from that for crystals grown at rest, but above 0.1 mm the size increased, by more than a factor 3 at 0.2 mm. Figure 3 illustrates these effects.Optimal vibration reduces D by improving the growth conditions (reduction of temperature gradients by mixing, more uniform impurity distribution).     

Spin resonance of irradiated luminescent LiH crystals

ESR line width and strength are reported for crystals exposed at room temperature to the unfiltered light of a SVD-120 mercury arc and to the electrons from a betatron operated at 8–10 MeV. There is a knee in the fall in the intensity and in the increase in the line width at 90 °–120 ° C (g = 2.001 ± ± 0.001) for crystals showing blue fluorescence. The relation of the ESR spectrum to the optical absorption and to the luminescence centers is discussed.We are indebted to M. D. Lemberberg for assistance in recording the optical absorption spectra of LiH.     

Far-infrared study of impurity local modes in gallium-doped PbTe

We present far-infrared reflection spectra and results of galvanomagnetic measurements of PbTe single crystals doped with gallium between 10 and 300 K. The analysis of the far-infrared reflection spectra was made by a fitting procedure based on the model of coupled oscillators. Together with the strong plasmon–phonon coupling we obtain three local modes of gallium at about 122, 166 and 192 cm⁻¹. The position of these modes depends of impurity center charge, and their intensity depends of temperature and of gallium concentration. Persistent photoconductivity effect was registered in the sample with 0.4 at.% Ga by galvanomagnetic and far-infrared measurements.     

Luminescence of rare gas crystals at high excitation densities for VUV laser applications

Exciton densities of the order of 10¹⁸ cm^–3 are generated in 0.1–0.3 mm thick surface layers in an area of 10×20 mm² of optically clear rare gas crystals. The quantum efficiencies at 126 nm (Ar), 145 nm (Kr), and 172 nm (Xe) remain near 0.5 even for the highest excitation densities. The corresponding gain coefficients of 2.6 cm^–1 (Ar) to 18 cm^–1 (Xe) exceed those of high pressure gas lasers by a factor of 20. Stimulated emission is inferred by observing the line narrowing, the dependence of intensities and time courses on excitation density and amplification measurements. The net gain coefficient is reduced however to 0.5–1 cm^–1 by transient absorption of excited centers and scattering by irradiation induced defects. The results are analysed by a system of rate equations for the excitation, relaxation, quenching, and amplification processes. A peculiar temperature dependence of the quantum efficiencies and time courses is attributed to electron trapping at grain boundaries.     

Design of multiple layered a-Si:H(F)/a-SiGex:H(F) films for enhancement in photoresponse in the near-infrared spectrum

Photo-electric properties of a-Si:H(F)/a-SiGe_x:H(F) multilayer films were investigated by measurements of optical absorption, and photoconductivity in both steady and transient modes with the repetition length and the difference in the optical gap between a-Si:H(F) and a-SiGe_x:H(F) as the variables. Measurements of primary photocurrent clarified that photosensitivity for the multilayer films extended to longer wavelengths of around 725 nm, while high resistivity was maintained despite of lowering the band gap.The drift mobility of electrons was measured by the time-of-flight technique, showing 10^–2-10^–3 cm²/Vs, while the drift mobility-lifetime products of electron was maintained to be 10^–7 cm²/V. On the other hand, the drift mobility of holes was 10^–3 cm²/Vs, which was the similar magnitude to that of a-Si:H(F).