MONITORING OF CDTE ATOMIC LAYER EPITAXY USING IN-SITU SPECTROSCOPIC ELLIPSOMETRY

Atomic layer epitaxy or ALE has proven to be useful for the growth of epitaxial layers of high uniformity, good quality, and well-controlled thickness. In this study, we have carried out in-situ monitoring duri ng the atmospheric pressure ALE of CdTe on GaAs (100) substrates using spectroscopic ellipsometry (SE). The susceptor temperature, reactant partial pressures, as well as the flow and flush duration for each pre cursor are crucial process variables for ALE growth. Growth was carrie d out for 20-25 cycles under different sets of these process condition s during the experiment and in-situ SE was used to verify the presence of layer-by-layer growth, which enabled the quick determination of th e process window. We observed ALE growth of CdTe at 300 degrees C, sup porting the explanation that the growth of CdTe occurs via a surface c atalyzed decomposition of the Te precursor di-isopropyltelluride (DIPT e). Investigation of ALE mode growth behavior for different susceptor temperatures and DIPTe flush times indicated that the growth was limit ed by competition between desorption and reaction of the adsorbed DIPT e species on the Cd terminated surface.