Two types of etch pits in cadmium telluride have been observed. The etchants used are nitric acid solutions of potassium bichromate which also contain silver ions of various concentrations. The etch pits resulting from etch (EAg-1) grow into a tetrahedral shape bounded by the crystallographic habit planes and reveal geometrical polarity on the (111) and (1̄1̄1̄) surfaces. Another type of etch pit is formed at a different point from that of the pit with EAg-1 by the modified etch (EAg-2), which has increased content of Ag+ ion. The two types of etch pits, with EAg-1 and with EAg-2, are believed to be associated with Cd and Te edge dislocations. The dissolution rate and its selectivity to the constituent elements in cadmium telluride is controlled electrochemically by the variation of the Ag+ ion concentration of the etching solution. The structure of the twin boundary is also studied by etching and back Laue techniques.
An ideal metal-semiconductor Schottky barrier contact was made by chemically depositing thin films of molybdenum on n-type silicon by the hydrogen reduction of molybdenum pentachloride at temperatures between 390°C and 500°C. Current-voltage, capacity-voltage, and photoelectric measurements were used to investigate the characteristics of molybdenum-silicon diodes thus produced. The junction is shown to be very close to the ideal Schottky barrier with the barrier height measured with respect to the Fermi energy of 0.57±0.02 eV.
It seems probable that two types of 60° edge dislocation exist in CdTe because of the geometrical polarity. In fact, such types of dislocations can be made visible as different etch pit figures with two kinds of etches. Two types of bendings were applied for the introduction of either excess-Cd or excess-Te dislocations. On each bending two types of dislocations were simultaneously brought about with a minimum in density near the neutral plane. However, annealing at high temperature resulted in a uniform distribution of dislocations and a polygonization of the crystal. Furthermore, it was found that dislocations of the correct sign, necessary to produce the required configuration of bending, were predominantly conserved while unexpected dislocations were thermally annihilated during the polygonization process.
crystal diameter is that for smaller crystal diameters the edge effects are of increasing importance, i.e., the rotating disk analysis ceases to be valid and the boundary layer thickness becomes a function of the radius.
SummaryThe radial solute segregation in Czochralski-grown silicon crystals has been shown to be greatly influenced by the effects of secondary liquid flow in the outer regions of the solid-liquid interface. The existence of interface facets will also cause large radial segregation because of the orientation dependence of the equilibrium distribution coefficient. However, the effects of liquid flow must be studied independently if unambiguous information is required on the facet effect alone. Maximum radial solute uniformity is possible only when the diffusion boundary layer at the growing interface is primarily controlled by crystal rotation, when the factor Oke/08 for the solute is insensitive to changes in 5 at any particular growth rate and when the crystal orientation does not permit the development of an extensive close-packed interface facet on an otherwise curved interface.
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