Photosensitive structures based on CdGa2Se4 single crystals

Semiconductors - Photosensitive structures based on CdGa2Se4 single crystals have been fabricated for the first time: In/CdGa2Se4 surface-barrier structures and InSe/CdGa2Se4 heterostructures. The...     

Photosensitivity of structures based on ZnSe single crystals

Heat treatment in vacuum and air was used to produce photosensitive structures based on ZnSe single crystals. Spectral dependences of relative quantum efficiency of photoconversion in these structures under exposure to natural and linearly polarized light were studied. The polarization photosensitivity of ZnSe-based structures was detected and studied in relation to their manufacturing conditions and photodetection configuration. Photopleochroism in these structures was shown to arise at oblique incidence of polarized light. The heat treatment of ZnSe in atmospheric air was demonstrated to reduce photopleochroism, which is related to interference phenomena in the formed layers. It was concluded that ZnSe can be employed in polarimetric short-wavelength photodetectors. This study represents a new approach to diagnostics of interaction processes at the ZnSe surface.     

Photosensitive structures based on boron phosphide single crystals

Boron phosphide single crystals are grown by steady-state crystallization. New photosensitive structures, In/p-BP and H₂O/p-BP, are suggested and fabricated. Steady-state I-V characteristics and spectra of the relative quantum efficiency of photoconversion of the structures obtained are studied. The type and energy of direct and indirect interband transitions are determined. It is concluded that the boron phosphide structures produced can be used in practice.     

Photosensitive structures on single crystals of MnIn2S4: Preparation and properties

Uniform single crystals of a ternary compound MnIn₂S₄ have been grown by the method of directional crystallization of an almost stoichiometric melt. The problem of the creation of photosensitive structures has been solved and the first studies of the spectra of photosensitivity have been performed, which made it possible to draw a conclusion on the nature of interband optical transitions in this semiconductor and to estimate the width of the energy gap for the direct and indirect transitions. The possibility of the application of the new structures in wideband photoconverters of optical radiation is noted.     

Photoelectric and photovoltaic properties of structures based on mesoporous silicon passivated with iron

The photoelectric and photovoltaic properties of structures based on mesoporous silicon passivated with iron (SiMP:Fe) are studied. It is shown that these properties ambiguously depend on the iron concentration. In the case of a sample with space-charge-limited currents (SCLCs), the charge-transport mechanism in the Al-SiMP:Fe-p-Si-Al heterostructure changes under illumination from the SCLC type to the barrier type. Passivation with 0.1–0.2 at % iron stabilizes not only the electrical, but also the photoelectric and photovoltaic properties of the structures. A further increase in the Fe concentration gives rise to new traps caused by the appearance of iron and silicon oxides, which leads to instability of the properties. The structures exhibit high sensitivity under low-level illumination. The open-circuit voltage is 16 mV under AM-1 irradiation (～2 mW/cm²).     

Photoelectric properties of Hg1−x CdxTe single crystals grown from the vapor phase

The electrical and photoelectric properties of Hg_0.1Cd_0.9Te crystals grown by chemical vapor transport are investigated experimentally. The temperature dependences of the carrier concentration and mobility are determined. The photoelectric properties of these crystals fit a model based on the existence of fast and slow recombination centers. Fiz. Tekh. Poluprovodn. 33, 1420–1422 (December 1999)     

Optoelectronic effects in semi-insulating CdTe single crystals and structures based on them

The authors describe a gas-transport reaction method they recently developed using the compounds NH₄Cl (Br, I) as transport agents. Using this method, they were able to grow semiinsulating cadmium telluride single crystals with carrier concentrations p=10⁸–10¹⁰ cm⁻³ at T=300 K. These crystals were used to fabricate In-CdTe surface-barrier structures with peak voltaic photosensitivities of ∼10⁵ V/W. Their investigations of the emission properties of homogeneous crystals at T=77K and distinctive features of their photosensitivity spectra revealed that these material characteristics derive from the use of Cl, Br, and I as dopants. By illuminating their In-CdTe structures with linearly polarized light at oblique incidence, they generated induced photopleochroism, which was measured and used to determine the refraction index of the material, which is found to be n=2.8. The paper concludes with a discussion of how these structures can be used as photodetectors of natural and linearly polarized light. Fiz. Tekh. Poluprovodn. 33, 553–558 (May 1999)     

Preparation and properties of GeS2 single crystals

Single crystals of GeS₂ are grown by two methods: crystallization from a melt and chemical vapor transport. All crystals are found to have a monoclinic structure with the unit-cell parameters a=11.45 Å, b=16.09 Å, c=6.7 Å, and β=91°. The reflection and transmission spectra are measured in the region of the absorption edge. The gap width is found to be equal to 3.2 eV.     

Surface-barrier structures on single crystals of CdMgMnTe quaternary solid solutions: Creation and properties

Planar melt crystallization is used to grow single crystals of Cd-Mg-Mn-Te quaternary alloys along the pseudobinary sections Cd_{0.75 − x} Mg _x Mn_0.25Te, Cd_{0.75 − x} Mg_0.25Mn _x Te, and Cd_{1 − 2x} Mg _x Mn _x Te. The first photosensitive structures, i.e., In/CdMgMnTe Schottky barriers, are fabricated within each indicated single-crystal section. The spectral dependences of the relative quantum efficiency of photoconversion are measured, and the broadband photosensitivity of the new structures is detected. Based on the spectral dependences of the photosensitivity, the nature of the meson transitions is discussed and the corresponding band gaps are determined. The applicability of grown single crystals of CdMgMnTe quaternary alloys to broadband photoconverters of optical radiations is ascertained.     

Electrical properties of Zn3P2 single crystals

The electrical properties of Zn₃P₂ single crystals grown by sublimation and by iodine transport, as well as largegrain polycrystalline material grown by sublimation, have been measured by conductivity and Hall effect measurements as a function of temperature. In single crystals scattering is controlled by charged impurity scattering at low temperatures and acoustic lattice scattering at high temperatures, with a typical maximum mobility value of 10 to 20 cm²/V-sec. In polycrystalline samples the mobility is thermally activated with an activation energy of 0.072 eV at higher temperatures and 0.028 eV at lower temperatures. A computer modelling of the Hall effect and conductivity data indicated acceptor levels with ionization energies of ≤_ 0.02 eV, 0.25 eV and 0.47 eV for the sublimed crystals, and of 0.034 eV and 0.14 eV for crystals grown with iodine transport; densities for these levels were also determined. Results of investigation of electrical contacts, vacuum heat treatment, and Auger profiling are also reported.     

Photosensitive structures based on ZnP<Subscript>2</Subscript> single crystals of monoclinic and tetragonal modifications: Fabrication and properties

The method of gas-phase resublimation is used to grow the single-crystals of monoclinic and tetragonal modifications whose composition are identical and corresponds to the ZnP₂ stoichiometry. The crystal-lattice parameters are determined and natural facets of the crystals of both modifications are identified. The obtained single crystals were used to fabricate for the first time the Schottky barriers and welded point structures; the latter exhibited rectification and the photovoltaic effect. On the basis of the first studies of photosensitivity of obtained structures subjected to the natural and linearly polarized radiation, the character of interband transitions is suggested, the values of the band gap are determined, and the influence of the position ordering of atoms on the structures’ properties is observed. The phenomenon of natural photopleochroism observed in the structures based on oriented ZnP₂ single crystals were studied. It is concluded that it is possible to use the zinc diphosphide in photoconversion of the intensity and polarization of optical radiation.     

Photoelectrochemical cells based on In2S3 single crystals

The single crystals of tetragonal modification t-In₂S₃ are grown by the planar crystallization of the melt. On their basis, the photosensitive H₂O/t-In₂S₃ cells are fabricated, and the spectra of their quantum efficiency are investigated. The broadband photosensivity of H₂O/t-In₂S₃ cells is determined. On the basis of the photosensivity spectra, the character of interband transitions and the t-In₂S₃ band gaps corresponding to them are determined. The possibility of using the t-In₂S₃ crystals in broadband photoconverters of natural and polarized radiations is shown. The relation between the energy spectrum and the phase state of In₂S₃ crystals is revealed.     

Electrical properties of CuInSe2 single crystals

Various bulk electrical properties and device characteristics have been measured. It has been shown that the majority carrier type is dependent on crystal stoichiometry. Mobilities of 660 cm²/V sec and 30 cm²/V sec have been measured for n-and p-type samples, respectively. Rectifying contacts and p-n junctions have been investigated by small signal analysis and the associated doping levels and equilibrium band diagrams have been determined. Photovoltage measurements on rectifying contacts have shown that the band-gap has a value of 0.95 ± 0.01eV.     

Electric and luminescence properties of GaAs-AIIBIVC 2 V single crystals

GaAs-A^IIB^IVC ₂ ^V single crystals are grown by crystallization from dilute gallium fluxed solutions. The electric and luminescence properties of the crystals obtained are investigated. It is shown that the technological process is accompanied by the standard doping of gallium arsenide and makes it possible to grow gallium arsenide single crystals whose optoelectronic properties are controlled by the A^IIB^IVAs₂ compound introduced into the fluxed solution. Fiz. Tekh. Poluprovodn. 33, 697–700 (June 1999)     

Photoelectric properties of ZnO/CuPc/Si structures

n-ZnO:Al/CuPc/n(p)-Si structures were formed using vacuum-evaporation deposition of copper phthalocyanine (CuPc) layers on the surface of n-and p-Si wafers with subsequent magnetron-sputtering deposition of ZnO:Al layers on the CuPc surface. It is shown that the structures obtained exhibit a high photosensitivity (～80 V/W at T=300 K) in the spectral range 1.65–3.3 eV. The rectification factor and photovoltaic effect in these structures are discussed in relation to the properties of silicon substrates. It is concluded that the contact of phthalocyanine with diamond-like semiconductors (e.g., silicon) are promising for application in wide-band high-efficiency photovoltaic converters.     

柔版印刷金属网栅光电性能研究

为满足日渐增加的电磁屏蔽要求,设计了一种透明基材上柔版印刷电磁屏蔽用金属网栅,研究了影响金属网栅透光率与电磁屏蔽特性的主要因素。首先从理论分析入手,计算并分析金属网栅结构参数（线宽、周期、占空比）等对透明导电金属网栅透光率及电磁屏蔽效能的影响;接下来利用柔版印刷方式制备周期为300、400 ｍ线宽为20、30、40 ｍ的金属网栅,测试了在7、10、13 GHz3个频点处电磁屏蔽效能以及300~1 000 nm波段的紫外-可见透过率。测试与分析结果表明:金属网栅在紫外-可见光波段透过率在70%~80%之间,且随周期/线宽增大而分别增大/减小,电磁屏蔽效能最高达到了15 dB以上。结果显示,网栅的光电特性是矛盾的,线宽与周期越小电磁屏蔽效果越好。     

Growing FeIn2S4 single crystals and fabrication of photosensitive structures on their basis

Bulk single crystals of FeIn₂S₄ have been grown for the first time by the method of directional crystallization of an almost stoichiometric melt. The first photosensitive structures of the In(Al)/FeIn₂S₄ have been fabricated. Using the crystals grown, the first spectra of photosensitivity of the new structures have been obtained at T = 300 K. Based on an analysis of the photosensitivity spectra, it has been established that the edge absorption of FeIn₂S₄ is formed by indirect and direct interband transitions, and the values of the energy gap corresponding to these transitions have been estimated. A conclusion was made on the possibility of applying the structures obtained in wideband photoconverters.     

Photoelectric signatures of CdZnTe crystals

To reveal the distribution of evident and latent electrically active defects of various types and different scales that affect the photoresponse of Cd_{1 − x} Zn _x Te alloys (x = 0.05–0.2), it is suggested to compare local photoelectric signatures U–I(y) _{f, λ} of various segments of the sample (U is the testing voltage, I is the photocurrent, y is the coordinate, λ is the wavelength, and f is the frequency of the testing signal), while, for the search of local instabilities of photoresponse, totality of integrated signatures U–I(Δy) _{f, λ} is most suitable. It is shown for the first time that the multiple scale and coordination of the fields of defects and acting field generate the spectral features of the photoresponse (reconstruction of the spectra and manifestation of latent photosensitivity bands), which are most completely and integratively reflected in signatures of the photocurrent spectra I(λ)–dI/dλ.     

Effect of rhenium doping on various physical properties of single crystals of MoSe2

正Effect of rhenium doping is examined in single crystals of MoSe_2 viz.MoRe_(0.005)Se_(1.995), MoRe_(0.001)Se_(1.999) and Mo_(0.995)Re_(0.005)Se_2,which is grown by using the direct vapor transport(DVT) technique. The grown crystals are structurally characterized by X-ray diffraction,by determining their lattice parameters a and c,and X-ray density.Also,the Hall effect and thermoelectric power(TEP) measurements show that the single crystals exhibit a p-type semiconducting nature.The direct and indirect band gap measurements are also undertaken on these semiconducting materials.     

Optical properties of synthetic diamond single crystals

Semiconductors - Synthetic diamond single crystals were grown by the thermal gradient method in a high-pressure apparatus in the presence of solvent catalysts (nickel, iron). Absorption,...