Close spaced sublimation is a technique commonly used to grow polycrystalline CdTe films for solar cell applications. Few studies have been done with this technique in regard to epitaxial growth of cadmium-telluride (CdTe) films. CdTe is a direct bandgap semiconductor, making it ideal for the use of solar cells and infrared detectors. The ability to grow high quality CdTe films CdTe films using the CSS technique will be beneficial to both applications.
This study analyzed the growth of CdTe on two different reactors: a simple closed spaced sublimation reactor that uses a single source CSS II and a novel closed spaced sublimation reactor that uses a three elemental source CSS III. Two types of substrates were used in this study, CdTe (211) and Si (211).
It has been shown that CdTe epitaxial films have been grown on both CdTe (211) and CdTe(111) substrates by different techniques. CdTe has also been grown on Si (211) using a ZnTe buffer layer.
CdTe (211) and Si (211) substrates were used for CdTe growth using the CSSII reactor. The preliminary parameters used were based on a previous study done by Arev Escobedo, a fellow graduate student. A high quality CdTe film grew epitaxially on the CdTe (211) substrates at low temperatures. The growth is sensitive to the preparation of the sample. A high quality film did not grow on the Si (211) substrates, instead it grew in clusters.
Only Si (211) substrates were used for growth experiments using the CSSIII. The parameters were based on equivalent vapor pressure calculations for each element. An annealing treatment was incorporated into the growth recipe. It was desirable to obtain a ratio of 1:1 between Cd and Te.
