PRODUCTION OF p-CdTe FILMS USED IN SOLAR CELL PRODUCTION BY CRYOGENIC SUBSTRATE EFFECT


Manır M. , Genç G., Tomakin M. , Ilık B., Nevruzoğlu V.

International World Energy Conference, Kayseri, Turkey, 3 - 04 December 2021, pp.176-182

  • Publication Type: Conference Paper / Full Text
  • City: Kayseri
  • Country: Turkey
  • Page Numbers: pp.176-182

Abstract

Semiconductor materials (CdS, CdTe, CdSe, ZnS and ZnSe) belonging to the AIIBVI group are widely used in photodevice production due to their characteristic properties. On the other hand, the high vapor pressure (S, Se, Te) of this group of semiconductors causes defects to occur during production. For this reason, it is a difficult technological process to produce the said materials perfectly on heated substrate surfaces. With the effect of temperature, defects such as donor cadmium interstitials (Cdi) and acceptor sulphur, tellurium, selenium cavities (VS, VTe, VSe) are formed in the crystal structure, giving the structure n-type electrical conductivity. Film formation on a heated substrate surface occurs by islet growth mechanism and displays a porous structure. This situation hinders the production of nano-sized photodevices. As can be seen, it is important to develop new technological methods in the production of non-porous nanoscale semiconductor films with high vapor pressure. Film production is carried out on the surface of the cooled substrates with the cryogenic substrate effect mechanism designed by us. This apparatus consists of two main parts, the cooler and the reactor parts. In the cooler part, there is a copper tube that can circulate liquid nitrogen for cooling the samples, and in the reactor part, there is the saturated vapor of the evaporated material. The film formation takes place thanks to the equal sized clusters carried from the saturated vapor medium to the substrate surface. The formation of clusters in saturated vapor environment will prevent the occurrence of Cdi and VTe defects. In this study, CdTe films were produced in the substrate temperature range of 100-300 K and their characteristics were investigated. From the XRD diffraction patterns, it was observed that there was reflection from the (111), (220) and (311) planes of the cubic structure. The energy band gap of the film produced at a substrate temperature of 200 K was calculated as Eg = 1.53 eV. From electrical measurements, the resistivity of the film produced at 200 K substrate temperature was calculated as ρ=6.63x103 Ohm.cm and carrier density N=5.68 x1016 cm-3 . The films produced from the hot point probe method and Hall measurements was found to have p-type electrical conductivity. From the initial results, it was understood that low-cost photodevices can be widely produced on the basis of high vapor pressure semiconductors using the cryogenic substrate technique.