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We report the epitaxy of n-Ge layer with in situ phosphorus (P)-doping using metal-organic chemical vapor deposition (MOCVD) method with tertiary-butyl-germane and tri-ethyl-phosphine precursors. The crystalline and electrical properties of n-Ge epitaxial layers have been investigated using X-ray diffraction, atomic force microscopy, and Hall effect measurements in detail. In situ P-doping with MOCVD demonstrates the incorporation of P in Ge as high as 1 × 1020 cm−3. The electron concentration in P-doped Ge epitaxial layers are achieved as high as 1.7 × 1019, 1.8 × 1019, and 2.2 × 1018 cm−3 at growth temperatures of 400, 350, 320 °C, respectively.

Selective epitaxial growth of Ge and Ge1−xSnx layers on Si substrates was performed by using metal-organic chemical vapor deposition (MOCVD) with precursors of tertiary-butyl-germane (t-BGe) and tri-butyl-vinyl-tin (TBVSn). We investigated the effects of growth temperature and total pressure during growth on the selectivity and the crystallinity of the Ge and Ge1−xSnx epitaxial layers. Under low total pressure growth conditions, the dominant mechanism of the selective growth of Ge epitaxial layers is the desorption of the Ge precursors. At a high total pressure case, it is needed to control the surface migration of precursors to realize the selectivity because the desorption of Ge precursors was suppressed. The selectivity of Ge growth was improved by diffusion of the Ge precursors on the SiO2 surfaces when patterned substrates were used at a high total pressure. The selective epitaxial growth of Ge1−xSnx layer was also realized using MOCVD. We found that the Sn precursors less likely to desorb from the SiO2 surfaces than the Ge precursors.

The epitaxial growth of a Ge1 − xSnx layer was examined using metal-organic chemical vapor deposition (MOCVD) with two types of Ge precursors; tetra-ethyl-germane (TEGe) and tertiary-butyl-germane (TBGe); and the Sn precursor tri-butyl-vinyl-tin (TBVSn). Though the growth of a Ge1 − xSnx layer on a Ge(001) substrate by MOCVD has been reported, a high-Sn-content Ge1 − xSnx layer and the exploration of MO material combinations for Ge1 − xSnx growth have not been reported. Therefore, the epitaxial growth of a Ge1 − xSnx layer on Ge(001) and Si(001) substrates was examined using these precursors. The Ge1 − xSnx layers were pseudomorphically grown on a Ge(001) substrate, while the Ge1 − xSnx layer with a high degree of strain relaxation was obtained on a Si(001) substrate. Additionally, it was found that the two Ge precursors have different growth temperature ranges, where the TBGe could realize a higher growth rate at a lower growth temperature than the TEGe. The Ge1 − xSnx layers grown using a combination of TBGe and TBVSn exhibited a higher crystalline quality and a smoother surface compared with the Ge1 − xSnx layer prepared by low-temperature molecular beam epitaxy. In this study, a Ge1 − xSnx epitaxial layer with a Sn content as high as 5.1% on a Ge(001) substrate was achieved by MOCVD at 300 °C.

In this study, we have examined the formation of uniaxially strained Ge microstructures with embedded Ge 1 − x Sn x epitaxial layers and the microscopic local strain structure in Ge and Ge 1 − x Sn x using synchrotron X-ray microdiffraction and the finite element method. We achieved local heteroepitaxial growth of Ge 0.947 Sn 0.053 layers on the Ge recess regions. Microdiffraction measurements reveal that an average uniaxial compressive strain of 0.19% is induced in Ge locally with Ge 1 − x Sn x stressors. In addition, we found that the Sn precipitation near the Ge 1 − x Sn x /Ge(001) interface occurs after post-deposition annealing at 500 °C without the introduction of dislocation. It is considered that the local Sn precipitation occurs preferentially due to the larger residual stresses near the Ge 1 − x Sn x /Ge interface.

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

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.

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.

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.