Articles you may be interested inEvolution of fcc Cu clusters and their structure changes in the soft magnetic Fe85.2Si1B9P4Cu0.8 (NANOMET) and FINEMET alloys observed by X-ray absorption fine structure

We have examined the epitaxial growth of Ge1-x-ySixSny layers on Ge substrates with a Sn content of 3~15% with low temperature molecular beam epitaxy method. The Ge1-x-ySixSny layers are psuedomorphically grown on Ge substrates with high crystalline quality. The surface morphology of the Ge1-x-ySixSny layers with a Sn content below 7% shows very flat and uniform, although surface roughening occurs in the sample with a Sn content as high as 15% provably due to the Sn precipitation. We also roughly estimated the energy band structure with liner approximation calculation. The energy bandgap of Ge1-x-ySixSny alloy prepared in this study is expected to be 0.8~1.0 eV at the L or X point.

The distributions of Sn concentration in GeSnSi layers formed on Ge substrate at various temperatures were investigated. High deposition temperature (Td) induces significant Sn migration and desorption, which have activation energies of 0.65 eV and 0.27 eV, respectively. A model quantitatively clarified the Sn migration fluxes during the deposition, which increase not only with increasing Td but also with the layer thickness. A non-negligible Sn flux compared with the supplied flux was found at 350 C at the surface of the 200-nm-thick layer. Consequently, designs of layer thickness and Td taking into account the appropriate Sn flux are important to form a GeSnSi layer with uniform Sn content for future optoelectronics

We experimentally demonstrated the formation of type-I energy band alignment in lattice-matched Ge1−x−ySixSny/Ge(001) heterostructures and clarified the dependence of Si and Sn contents on the energy band structure. By controlling the Si and Sn contents, keeping the Si:Sn ratio of 3.7:1.0, we formed high-quality Ge1−x−ySixSny pseudomorphic epitaxial layers on a Ge substrate with the lattice misfit as small as 0.05%. The energy bandgaps of the Ge1−x−ySixSny layers, measured by spectroscopic ellipsometry, increased to 1.15 eV at Si and Sn contents of 41% and 15%, respectively. X-ray photoelectron spectroscopy indicated that the top of the valence band of Ge1−x−ySixSny was lower than that of Ge. Additionally, the energy band offsets between Ge1−x−ySixSny and Ge at both the conduction and valence band edges were estimated to be larger than 0.1 eV with an Sn content of more than 8%. These results promise that heterostructures of group-IV semiconductors using Si, Ge, and Sn can have type-I energy band alignment without relying on strain and can confine both electrons and holes.