Amorphous silicon(a-Si) stripe p-i junction photodiode array for contact-type image sensor of a facsimile has been developed and investigated especially with regard to its unsymmetrical electrode structure. This sensor consists of a p-i a-Si stripe layer, Cr separate electrodes, and an ITO common electrode. As a result, it is found that the photosensitive region of a-Si stripe type photodiode exists not only in a-Si sub-region having both upper and lower electrodes but also in a-Si sub-regions having upper or lower one-sided electrode. It is considered that photocarrier collecting mechanisms in the a-Si sub-regions are different and result to the different photodiode characteristics.

Tellurium-based chalcogenide alloys, which are used for electronic switch materials, also have the appropriate optical and thermal properties for reversible optical data recording. One of the major concerns encountered with this type of phase change material is that there can be two contradictory characteristics of the material, i.e., the amorphous phase thermal stability and the crystallization rate are involved. We have demonstrated, in this paper, that this problem can be solved. We report that certain transition metal elements added to Te alloy films can substantially improve the rate of crystallization without any reduction of the amorphous phase stability.

The optical properties and the thermal stability of Ge and Sn doped TeOx films prepared by coevaporating TeO2, Te, Ge and Sn are reported. These films are amorphous as-deposited and crystalline Te appears after annealing at, e.g., 100 to 250°C. As expected, the addition of Ge and Sn increases the absorption of the TeOx films at the wavelength of interest (e.g., 830 nm). However, the thermal stability of (TeO1.1)1-xGex (x=0 to ~0.7) films is found to decrease with increasing x initially, starting to increase with increasing x only after x reaches a value between 0.3 and 0.4. These results differ from those reported previously for Ge and Sn-doped TeOx films and from those observed for Te-Ge alloy films. Interpretations of these results based on a solid state reaction between TeO2 and Ge or Sn during deposition are presented and discussed.

Erasure speed and thermal stability of a number of Te-based alloys have been measured and compared. A distinct trend of increasing crystallization temperature, Tx, and increasing minimum time required for crystallization, τx, with increasing crosslinking element content is observed. Films which crystallize to form Te are stability limited at Tx≈80°C for τx≈┐μsec. Films which crystallize to form Sb40Te45Se15 have Tx160°C at τx≈┐μsec. Static tester recrystallization kinetics and direct observation of cycled tracks by optical and electron microscopy indicate that recrystallization occurs via epitaxial growth from peripheral crystallities and not from internally dispersed nuclei for all materials studied. Thus, crystallization speed is limited by three factors: the intrinsic maximum crystallization velocity of the pure crystal, the diffusion rate of crystal-insoluble crosslinking elements away from the crystallization front, and the geometry of the amorphous and peripheral crystalline zones

The transmittance spectra of amorphous As2S3 films prepared by two different techniques, namely spin coating and quenched from the melt were investigated. All measurements were done at room temperature in the energy range from 1.2 to 3.8 eV. The spin casted material was prepared by dissolving powdered stoichiometric arsenic trisulfide in amines and amides, the resulting solution spinned on an oxide glass substrate and baked to remove the volatiles. A typical resulting film was a few micrometers thick and microstructure free as characterized under an optical microscope. The quenched material was prepared by melting a stoichiometric mixture of the reactants in an evacuated and sealed ampoule and alloying at 1100°K for 15 hrs. The melt was subsequently quenched in air to obtain vitreous materials. The transmittance spectra of both types of samples was measured and from the spectra the refractive index dispersion, film thickness and absorption coefficient were obtained. A considerable difference between the optical constants of the spin casted samples and thermally evaporated ones was found. This was attributed to the incorporation of carbon and hydrogen in the amine salt alkyl group formed when dissolving the chalcogenide material.

The conductivity of a-Si:H multilayers consisting of alternating boron and phosphorus doped layers has been studied as a function of sub-layer thickness. The planar and perpendicular dark conductivity is compared with theoretical analysis of space-charge doping in these structures and this effect is found to dominate the transport as the sub-layer thickness is reduced below a critical value

High photoconductive a-Si:H(F) and St-based alloys were prepared from “precursors” made by oxidation of silane with F2 or reduction of SiFn (n=1,2,) with atomic hydrogen. Both crystalline and amorphous silicon were prepared at will, in the latter case, by controlling the flow of hydrogen. A marked reduction in the localized states in the vicinity of valence band was eatablished in the a-Si:H(F) prepared under optimal condition. A novel photoconductive film with high photoconductive gain for near-tr light was successfully made by multiplying a-Si:H/a-SiGe:H(F) periodically by a new preparation technique without a rise in the dark conductivity.