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

Epitaxial films of the wide-bandgap II–VI beryllium chalcogenide semiconductors, BeTe, BeSe, and BeSeTe were grown on arsenic-terminated silicon substrates by MBE. Silicon was also epitaxially regrown on Be-chalcogenide films. Initial structural characterization revealed the desired smooth two-dimensional 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 Se/Te flux ratio. The variation in Be/Se flux ratio or in the sticking coefficients due to temperature gradients led to radial compositional inhomogeneity. Current versus temperature measurements of the Be-chalcogenide films at elevated temperatures analyzed assuming thermionic emission over the heterojunction barrier, showed conduction band offsets of 1.2 eV for the BeSe_0.41Te_0.59/As/Si and 1.3 eV for the BeSe/As/Si heterostructures. At room temperature, current density through BeSe/Si and BeSe_0.41Te_0.59/Si films was mid-10 ^{− 9}A cm ^{− 2}at 0.1 MV cm ^{− 1}, similar to previously reported values for ZnS/Si, while BeTe/Si films had orders of magnitude higher current density, possibly due to interfacial recombination.