Shinichi Ike

Characterization of locally strained Ge1−xSnx/Ge fine structures by synchrotron X-ray microdiffraction

We have investigated the formation of the locally strained Ge nanostructure with epitaxial Ge1−xSnx stressors and characterized the microscopic strain field in the Ge1−xSnx/Ge fine-heterostructures by synchrotron X-ray microdiffraction and finite element method (FEM) calculations. We achieved local epitaxial growth of Ge1−xSnx with Sn contents of 2.9% and 6.5%, sandwiching the 25 nm-wide Ge fine line structure. Microdiffraction measurements revealed that out-of-plane tensile strain induced in the Ge line effectively increased with decreasing Ge width and increasing Sn content of Ge1−xSnx stressors, which is in good agreement with FEM calculations. An out-of-plane tensile strain of 0.8% along the Ge[001] direction is induced in a 25 nm-wide Ge line, which corresponds to an in-plane uniaxial compressive strain of 1.4% in the Ge line sandwiched between Ge0.935Sn0.065 stressors.

Influence of precursor gas on SiGe epitaxial material quality in terms of structural and electrical defects

We have investigated the structural and electrical properties of n-type doped Si1− x Ge x epitaxial layers (x = 24–26%) grown by chemical vapor deposition with conventional [SiH2Cl2 (DCS)/GeH4] and high-order (Si2H6/Ge2H6) precursor combinations. X-ray diffraction, atomic force microscopy, and deep-level transient spectroscopy (DLTS) measurements were performed for characterization. The crystalline properties and surface morphology of the Si1− x Ge x layer with Si2H6/Ge2H6 grown at temperatures as low as 550 °C show good structural quality similar to that with DCS/GeH4 grown at 615 °C. On the other hand, in terms of electrical properties, the DLTS measurement reveals the existence of vacancy-related complexes in the as-grown layer with Si2H6/Ge2H6. We found that post-deposition annealing at 200 °C for the Si1− x Ge x epitaxial layer is effective for annihilating vacancy-related defects with densities down to as low as that of conventional precursors.

Selective growth of Ge1− x Sn x epitaxial layer on patterned SiO2/Si substrate by metal–organic chemical vapor deposition

We have investigated the selective growth of a Ge1− x Sn x epitaxial layer on a line/space-patterned SiO2/Si substrate by metal–organic chemical vapor deposition. We examined the behavior of a Sn precursor of tributyl(vinyl)tin (TBVSn) during the growth on Si and SiO2 substrates and investigated the effect of the Sn precursor on the selective growth. The selective growth of the Ge1− x Sn x epitaxial layer was performed under various total pressures and growth temperatures of 300 and 350 °C. The selective growth of the Ge1− x Sn x epitaxial layer on the patterned Si region is achieved at a low total pressure without Ge1− x Sn x growth on the SiO2 region. In addition, we found that the Sn content in the Ge1− x Sn x epitaxial layer increases with width of the SiO2 region for a fixed Si width even with low total pressure. To control the Sn content in the selective growth of the Ge1− x Sn x epitaxial layer, it is important to suppress the decomposition and migration of Sn and Ge precursors.

Growth and applications of GeSn-related group-IV semiconductor materials

We have developed the epitaxial growth technology of Ge<inf>1−x</inf>Sn<inf>x</inf> and related group-IV materials. The crystalline properties and energy band structure have been investigated for integrating group-IV semiconductors into Si ULSI platform.