Growth of CdTe films on alternative substrates by molecular beam epitaxy

Growth of epitaxial CdTe films on silicon and sapphire substrates is discussed. The quality of the epitaxial CdTe films was determined from x-ray diffraction, UV reflectance, and photoluminescence measurements. CdTe epitaxy was achieved on both silicon and sapphire substrates using growth rates of 1–3 μm/h and substrate temperatures of 200–400 °C. The CdTe/sapphire epilayers, in particular, exhibit exceptional properties including a large photoluminescence at 77 °K, a large photoconductivity at room temperature, majority carrier (electron) lifetimes greater than 10−5 s at 300 K, and electron mobilities greater than 900 cm2/V s at room temperature. These mobilities are the largest ever reported for CdTe films grown by any technique. On the basis of these results, CdTe/sapphire epilayers appear to offer a viable alternative to bulk CdTe substrates for growth of HgCdTe, an important infrared detector material.