Аutomated method for determining the etch pits density on crystallographic planes of large semiconductor crystals

A method for express automatic evaluation of the dislocation density on the crystal surfaces has been developed. The work involves creation of a software that allows automatical determining the number of etch pits with a defined geometric shape, which are seen in the microscope view field, and calculation of the density of those etch pits. In addition, adaptation of a metallographic microscope for the above measurements has been made. The developed method can be used to greatly speed up the maping of etch pits density over the area of large crystals. For example, duration of about 400 measurements of etch pits density made in various sites of 330×150 mm surface of the optical germanium crystal plate and of maping the etch pits distribution over this surface made by the developed method is about 40 min, while duration of the same measurements made by the traditional method for visual counting the number of etch pits seen in the eyepiece of the microscope is several dozens of hours. Use of the described method has allowed us to determine the geometric position of maximum internal stress in large optical germanium plates grown by horizontal unidirectional crystallization. This method has been already included in the metrological complex of serial production of large-area plates made of Na-doped optical germanium – a new material of infrared technique, developed and introduced into production at the V. Lashkaryov Institute of Semiconductor Physics, NAS of Ukraine

Screen-printed p-CdTe layers for CdS/CdTe solar cells

Correlation of the recrystallization process technological parameters with the morphology and structure of screen-printed p-CdTe layers intended for CdS/CdTe solar cell fabrication has been established. The optimal regimes to form layers with required characteristics have been found. As distinct from the used previously screen-printing techniques for CdS/CdTe solar cell fabrication, CdTe layers were doped with Ag or Au not by their diffusion from the layer surface but in the course of layer preparation. For this purpose, tellurides of those metals were added into the raw paste used for CdTe screen printing. It is shown that the developed method has some advantages and allows to prepare CdTe films, structural and electrophysical parameters of which are suitable to fabricate CdS/CdTe solar cells

Recrystallization processes in screen-printed CdS films

Kinetics of recrystallization in screen-printed polycrystalline CdS films has been investigated by X-ray structure analysis and optical microscopy. The relation between the crystallite size, crystallite orientation and the macrostrain, as well as their dependence on heat treatment regimes is established. It is shown that single-phase CdS films having a thickness of some tens microns, large grain size and low residual strain can be produced at optimum technological regimes. The films obtained are suitable for fabrication of CdS/CdTe solar cells

Large polycrystalline optical germanium Ge:Na plates with improved optical parameters and their application

It has been experimentally shown that transmission and scattering of IR radiation by Na-doped соarse-grained large germanium plates are the same as of Ge:Na single crystals and exceeds the parameters in the commonly used optical germanium Ge:Sb grown from the same raw material. Being based on experimental results, a conclusion has been made that the nature of the dopant in Ge:Na is a decisive factor defining its optical parameters, along with the usual requirements of high purity of the raw material, resistance values below about 20 Ohm·cm and a sufficiently large grain size (for polycrystalline material). It is assumed that, most likely, Na in Ge:Na, contrary to Sb in Ge:Sb, doesn’t form impurity clouds that scatter the incident IR radiation. The advantages of the polycrystalline Ge:Na as a material for IR optics were proved when using it for industrial manufacturing the protective screens for night vision systems