Investigation of cadmium telluride nanohetero-epitaxy growth on silicon(100) substrates for mercury cadmium telluride infrared detector applications
The selective CdTe Nanohetero-Epitaxy growth on Si(100) substrates has been achieved without the use of a mask in an attempt to reduce the dislocation density at the CdTe/Si interface to 105/cm3 using the Close-Space Sublimation (CSS) technique, which is a low-cost effective technique for the deposition of polycrystalline CdTe films. Furthermore, CdTe is a compound semiconductor with a direct bandgap of 1.5 eV, which makes it an ideal material for the applications of infrared detectors and solar cells. It has been demonstrated that the selective growth of CdTe on patterned Si(100) substrates results in CdTe grains with smooth surfaces. For this reason, these high quality grains may be used for the subsequent growth of planar MBE CdTe followed by HgCdTe for the applications of Long-Wavelength Infrared (LWIR) detectors and Middle-Wavelength Infrared (MWIR) detectors. Several techniques have been used for the epitaxial growth of CdTe on Si, such as Molecular Beam Epitaxy (MBE), Liquid Phase Epitaxy (LPE), Hot-Well Epitaxy (HWE) and Metalorganic Vapor Phase Epitaxy (MOVPE); however, these techniques are expensive and have low growth rates. For this reason, special interest has been given to the CSS technique for the growth of CdTe such as its low-cost and higher growth rates (>1 μm/h). In this study, the first set of experiments consisted of the planar epitaxial growth of CdTe on CdTe(111) substrates, resulting in average growth rates between 5–10 μm/hr. The film with the most promising film morphology resulted from growth parameters, where Tsou = 530°C and Tsub = 350°C. The second set of experiments consisted of the planar epitaxial growth of CdTe on Si(100) substrates, resulting in average growth rates between 6–10 μm/hr. The same parameters used to produce the highest quality CdTe films on CdTe(111) were found to be optimum for Si(100) as well. The third set of experiments consisted of the selective epitaxial growth of CdTe on patterned Si(100) substrates, where CdTe selectively was achieved for all substrate and source temperatures analyzed without using a mask. This has never been observed before for CdTe deposited on patterned Si. Characterization methods such as scanning electron microscopy (SEM) and x-ray diffraction (XRD) were used to observe CdTe film and grain morphology and to analyze the structure and quality of the planar CdTe films. As a result, the characterization of these films confirmed that CSS can be an effective and low-cost technique for the planar and selective epitaxial growth of CdTe films.
Diaz, Aryzbe, "Investigation of cadmium telluride nanohetero-epitaxy growth on silicon(100) substrates for mercury cadmium telluride infrared detector applications" (2010). ETD Collection for University of Texas, El Paso. AAI1479553.