ATOMIC LAYER EPITAXY - 12 YEARS LATER

A review of the state of the art of atomic layer epitaxy (ALE) is presented. ALE is based on chemical reactions at the heated substrate surface to which the constituent elements of the crystallized film are delivered sequentially as pulses of neutral molecules or atoms. The thickness of the epitaxial layer is determined primarily by the number of exposure cycles and is much less sensitive to the growth time or reactant fluxes. The ALE growth mode may be realized in chemical vapor deposition, in high vacuum gas source molecular beam epitaxy, and in conventional molecular beam epitaxy. The latter case, called ultra-high vacuum ALE is discussed most widely in this review, with emphasis on the physical processes occurring in the near surface transition layer during the growth of II-VI and III-V semiconductor compounds. © 1990.