Structure of MBE grown semiconductor-atomic superlattices

A new type of superlattice, semiconductor-atomic superlattice, consisting o f multiple periods of semiconductor layers separated by adsorbed atomic/mol ecular monolayers, requires that the growth remains epitaxial. Specifically , the Si/O superlattices have been fabricated with epitaxially grown thin s ilicon layers (1-2 nm thick) separated by periodically introduced monolayer s of oxygen. High-resolution TEM shows defect density at the Si/O interface is below 10(9)/cm(2) Electroluminescence diodes show a peak in the yellow- green of the visible spectrum, and have been life-tested for over a year wi thout signs of degradation. Measured effective barrier height is between 0. 5 and 1 eV. Models of the structures, showing how epitaxy can be continued with a monolayer of oxygen, are presented. Preliminary calculation shows th at the strain is relatively low. The door is opened for device applications in silicon optoelectronics. (C) 2001 Elsevier Science B.V. All rights rese rved.