Development of epitaxial silicon lattice-matched insulators: silicon heterostructures for quantum confinement

Epitaxial films of the wide-bandgap II-VI beryllium chalcogenide semiconduc tors, BeTe, BeSe, and BeSeTe were grown on arsenic-terminated silicon subst rates by MBE. Silicon was also epitaxially regrown on Be-chalcogenide films . Initial structural characterization revealed the desired smooth two-dimen sional nature of the layer growth. The composition of BeSeTe ternary films was governed by the Be/Se flux ratio during deposition rather than by the S e/Te flux ratio. The variation in Be/Se flux ratio or in the sticking coeff icients due to temperature gradients led to radial compositional inhomogene ity. Current versus temperature measurements of the Be-chalcogenide films a t elevated temperatures analyzed assuming thermionic emission over the hete rojunction barrier, showed conduction band offsets of 1.2 eV for the BeSe0. 41Te0.59/As/Si and 1.3 eV for the BeSe/As/Si heterostructures. At room temp erature, current density through BeSe/Si and BeSe0.41Te0.59/Si films was mi d-10(-9) A cm(-2) at 0.1 MV cm(-1), similar to previously reported values f or ZnS/Si, while BeTe/Si films had orders of magnitude higher current densi ty, possibly due to interfacial recombination. (C) 2000 Academic Press.