GROWTH, CHARACTERIZATION AND DEVICE APPLICATIONS OF CADMIUM ZINC TELLURIDE THIN FILMS

2022-5-25
Doğru Balbaşı, Çiğdem
CdZnTe is an II-VI group semiconductor material with significant properties used in many critical industrial applications, such as photovoltaic devices, photodiodes, photoconductors, room temperature gamma-ray spectroscopy, X-ray imaging, and infrared detectors. In Particular, CdZnTe is a promising material for solar cell application as an absorber layer due to its direct tunable bandgap property, high atomic number with strong absorption, excellent optoelectronic properties, and long-term stability. However, manufacturing CdZnTe-based solar cells has been a challenge, with minimum improvement recorded over the years. Therefore, four main topics about CdZnTe thin films were studied in this dissertation: (a) growth mechanism and material optimization of CdZnTe thin films by using various investigative characterization techniques, (b) understanding the surface and interface chemical compositional properties and optical dielectric response of CdZnTe thin films, (c) fabrication and electrical characterization of CdS/CdZnTe device structure with thin absorber layer (<2.0 μm) deposited at low substrate temperatures with reduced post-deposition processes, and (d) a detailed electrical analysis of the CdZnTe/Si structure for possible device applications. In this dissertation, high-quality CdZnTe thin films were fabricated using a thermal evaporation method with uniform component distribution, which was controlled by utilizing CdZnTe single crystal pieces as source material. Additionally, post-deposition processes such as annealing and CdCl2 treatment steps were applied. As a result, improved material properties and enhanced device performance of CdZnTe thin films were obtained. After a careful characterization of material and surface properties, thin heterojunction CdS/CdZnTe and CdZnTe/Si devices were fabricated successfully. It is worth noting that semitransparent thin CdZnTe films (≤2.0 µm) had a transmittance value greater than 75% in the near-infrared region, around 1000 nm. Finally, the operation and performance of the CdZnTe-based devices were investigated, and challenges encountered in the development of these devices were explained in detail.

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Citation Formats
Ç. Doğru Balbaşı, “GROWTH, CHARACTERIZATION AND DEVICE APPLICATIONS OF CADMIUM ZINC TELLURIDE THIN FILMS,” Ph.D. - Doctoral Program, Middle East Technical University, 2022.