Ge growth on porous silicon: The effect of buffer porosity on the epilayer crystalline quality

Abstract

We report on the epitaxial growth of Ge virtual substrates directly on Si (001) and on different porosity porous silicon (pSi) buffers. Obtained results indicate that Ge grown on low porosity (22%) pSi buffer has a better crystalline quality compared to Ge grown on bulk Si and on higher porosity buffers. This result is attributed to the compliant nature of pSi and to its reduced Young’s modulus, which leads to plastic tensile deformation of the 22% porosity buffer under the in-plane tensile stress introduced by Ge lattice. The same result is not observed for higher porosity buffers, this effect being attributed to the higher buffer fragility. A low porosity pSi layer can hence be used as buffer for the growth of Ge on Si virtual substrates with reduced dislocation content and for the growth of Ge based devices or the successive integration of III-V semiconductors on Si

New strategies for producing defect free SiGe strained nanolayers

“…We can conclude that in these experimental conditions, while the PSi substrate is much softer, it has no influence on the development of the instability 41 . If we observe the corresponding simulation (for s = 0.1), we see that the instability could be considerably enhanced depending on .…”

Enhanced reduction in threading dislocation density in Ge grown on porous silicon during annealing due to porous buffer reconstruction

“…Nevertheless, the strong TDD reduction by almost one order of magnitude observed in the presence of pSi firmly points out that after optimization of growing conditions, very low TDD can be obtained for a 5 μm‐thick Ge epilayer on pSi, making Ge on pSi a promising template for III–V epitaxy. For as‐grown samples, a maximum TDD reduction of 40% was observed in the presence of pSi . The significantly stronger improvement in TDD observed in the presence of pSi after cyclic annealing clearly indicates the existence of a mechanism for TDD reduction at high temperature which is only effective for Ge on pSi and not for Ge on bulk Si.…”

“…(a), the (224) Omega/2Theta scans collected in GID configuration for Ge grown on pSi and on bulk Si are shown. For Ge grown on pSi, two different pSi sublayers compressed in the out‐of‐plane direction have been found after epitaxy, this effect being attributed to tensile strain and fracture of the porous buffer during epitaxy . A slightly sharper Ge diffraction peak is observed for Ge grown on pSi, indicating a more homogeneous strain distribution within Ge compared to Ge grown on bulk Si.…”

“…Epitaxy is carried out by low energy plasma enhanced chemical vapor deposition (LEPECVD) using GeH 4 as Ge source gas and H 2 as carrier gas. More details about pSi fabrication and Ge epitaxy are reported elsewhere .…”

“…In a former work , we have shown that TDD in Ge grown on Si can be reduced by introducing a low porosity (∼20%) porous silicon (pSi) buffer layer in between the Si substrate and the Ge epilayer, which can tensile strain during epitaxy, partially compensating for the lattice mismatch between Ge and Si. Other research groups have investigated the epitaxial growth of Ge on pSi showing very low values of RMS roughness can be obtained, i.e., suitable for subsequent epitaxy .…”