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Development of regular vertical p-n junction on nanocrystalline PbTe film
Polycrystalline nanograined p-type PbTe films were obtained by electron gun-assisted vapor deposition on 100 μm thick amorphous substrates. This part of the study included the establishment and tuning of fabrication technology regimes in terms of the films' composition and crystallites arrangement optimal for having best structural properties, such as dominant texture, tiny-sized or absent voids, and small surface roughness. For this synthesis, we used components' composition Pb0.999Te1.001 bearing in mind that any excess Te builds up an acceptor center. Then, from the thus prepared p-type films, their n-type counterparts were obtained by ion implantation of zinc. At suitable conditions of the implantation process, the inversion of p-type to overall n-type material was experimentally shown and qualitatively explained. The structural and transport properties of both types of films were investigated, demonstrating their high integrity and a moderate effect of grain boundaries. Vertical p-n junction structures were prepared in the p-type films by a combination of proper masking and ion implantation. An electron beam-induced current technique was applied to directly portray the transition between p-and n-sides of the film and to assess the diffusion length of the minority charge carriers. The transition proves rather sharp spatially, which points to a well-defined p-n junction. Increasing the diffusion length of charge carriers of these structures compared to that in epitaxial films was discovered. A possible explanation of this effect and device applications of the developed structure are suggested.