Closed-loop control of growth of semiconductor materials and structures by spectroellipsometry

Using closed-loop ellipsometric feedback control, we have grown a variety of epitaxial AlxGa1-xAs structures by chemical beam epitaxy where compositions x vary continuously with thickness according to a given input function. Present limits are exemplified by a 200 angstrom parabolic quantum well structure grown using compositions determined from the outermost running approximately 3 angstrom (approximately 1 monolayer) of depositing material.