Surface Recombination Velocity Dependence on Morphological Properties of CdTe Thin Films Prepared by Close-Spaced Sublimation

Abstract

Cadmium telluride (CdTe) thin films were prepared on glass substrates by employing the close-spaced sublimation technique. Different source ($T_\mathrm{sou}$) and substrate temperatures ($T_\mathrm{sub}$) were used in order to change the structural properties of layers. The ranges chosen were: $550\,^{\circ }\hbox {C} \le T_\mathrm{sou} \le 650\,^{\circ }\hbox {C}$ and $400\,^{\circ }\hbox {C} \le T_\mathrm{sub} \le 600\,^{\circ }\hbox {C}$. The environment in the growing chamber was also changed with the purpose to study its influence on the crystalline properties of the surface and volume of the material. Three different surroundings were used: vacuum, high-purity argon, and high-purity oxygen. The surface recombination velocity (SRV) was calculated from photoacoustic (PA) measurements by employing the open PA cell configuration. The behavior of the experimental results was analyzed as a function of the structural characteristics of the films: texture and grain size. Scanning electron microscopy, optical absorption, X-ray diffraction, and dark resistivity measurements were also employed to analyze the properties of the CdTe films. The minimum value for the SRV was found for $T_\mathrm{sou} = 650\,^{\circ }\hbox {C},\, T_\mathrm{sub} = 600\,^{\circ }\hbox {C}$ in an oxygen ambient.