Epitaxial growth of CdTe using close-space sublimation (CSS), a relatively inexpensive deposition technique typically used for polycrystalline thin films, was achieved resulting in high quality smooth films on CdTe(111) substrates. Also, similar conditions were applied in the selective epitaxial growth of CdTe on CdTe/ZnTe/Si (211) substrates masked with a Si 3 N 4 patterned layer. Special attention has been given to the growth of CdTe films due to its promising potential applications in solar energy conversion and optoelectronic devices such as gamma ray and infrared detectors. Special interest in using CSS is due to its simplicity, cost-effectiveness, and relatively faster growth rates (>1 µm/hr) compared to conventional deposition techniques for epitaxial growth. Molecular Beam Epitaxy (MBE), Liquid Phase Epitaxy (LPE), and Metalorganic Vapour Phase Epitaxy (MOVPE) are a few examples of these deposition systems typically used to produce high quality epitaxial films.
This thesis presents several studies in which close-space sublimation was characterized over a wide range of experimental parameters to obtain the best conditions that yield a high quality epitaxial film of CdTe on the two above mentioned substrates. A CdTe(111) single crystal wafer with twins was used as a sublimation source. The films grown on the CdTe(111) substrates were characterized by profilometry, scanning electron microscopy (SEM recently purchased through NSF grant DMR-0521650), and x-ray diffraction (XRD). In particular, profilometry was used to calculate growth rates varying between 1 and 3.3µm/hr. SEM micrographs showed evidence of smooth films with grain coalescence due to annealing. Furthermore, XRD rocking curves demonstrated highly oriented single crystal films in the (111) direction. Moreover, selective growth of high quality CdTe posts was achieved on the patterned CdTe/ZnTe/Si(211) structure masked with a Si 3 N 4 as indicated by SEM. In general, all characterization results demonstrate that close-space sublimation is indeed a very promising low-cost technique for fast-growth-rate deposition of high-quality epitaxial CdTe films.
