In situHREM irradiation study of point-defect clustering in MBE-grown strainedSi1−xGex/(

Abstract

We present a detailed analysis of the point-defect clustering in strained Si/Si 1Ϫx Ge x /(001)Si structures, including the interaction of the point defects with the strained interfaces and the sample surface during 400 kV electron irradiation at room temperature. Point-defect cluster formation is very sensitive to the type and magnitude of the strain in the Si and Si 1Ϫx Ge x layers. A small compressive strain (Ϫ0.3%) in the SiGe alloy causes an aggregation of vacancies in the form of metastable ͓110͔-oriented chains. They are located on ͕113͖ planes and further recombine with interstitials. Tensile strain in the Si layer causes an aggregation of interstitial atoms in the forms of additional ͓110͔ rows which are inserted on ͕113͖ planes with ͓001͔-split configurations. The chainlike configurations are characterized by a large outward lattice relaxation for interstitial rows (0.13 Ϯ0.01 nm) and a very small inward relaxation for vacancy chains (0.02Ϯ0.01 nm). A compressive strain higher than Ϫ0.5% strongly decreases point-defect generation inside the strained SiGe alloy due to the large positive value of the formation volume of a Frenkel pair. This leads to the suppression of point-defect clustering in a strained SiGe alloy so that SiGe relaxes via a diffusion of vacancies from the Si layer, giving rise to an intermixing at the Si/SiGe interface. In material with a 0.9% misfit a strongly increased flow of vacancies from the Si layer to the SiGe layer and an increased biaxial strain in SiGe both promote the preferential aggregation of vacancies in the ͑001͒ plane, which relaxes to form intrinsic 60°dislocation loops.

Alternative mechanism for misfit dislocation generation during high-temperature Ge(Si)/Si (001) island growth

“…During the experiments, care was taken to avoid electron beam damage which could potentially create defects. 15 Figure 1 shows typical ͗110͘ cross-section bright-field TEM images of ͑a͒ a coherent island and ͑b͒ an incoherent island. Extensive TEM investigation from both plan-view and cross-section specimens indicates that the islands with base diameters as large as 100 nm are coherent.…”

Strain-facilitated process for the lift-off of a Si layer of less than 20 nm thickness

“…This effect has been previously observed in compressively strained SiGe layers. 15 Second, interactions of H with those vacancies which are agglomerated along ͑100͒ planes facilitate the formation of ͑100͒-orientated platelets. Various studies have proposed that vacancies play a central role in platelet formation.…”

Plasma hydrogenation of strained Si∕SiGe∕Si heterostructure for layer transfer without ion implantation

“…22 High resolution electron microscopy of electron irradiated strained Si has shown preferential aggregation of vacancies on ͑001͒ planes within the SiGe layer. 20 Various experiments have provided evidence that vacancies play a central role in H platelet formation. 12,13,23,24 Chemical interaction of H with dangling bonds in vacancytype defects, and subsequent trapping of hydrogen lead to the formation of H platelets and ultimately to the formation of H 2 gas bubbles.…”

“…Previous studies have shown an outward relaxation of the lattice around a self-interstitial in Si and an inward relaxation of the lattice around a vacancy. [19][20][21] Accumulation of interstitials within the compressively in-plane-strained SiGe layer is mediated primarily by vacancies diffusing towards the strained layer. 20 Furthermore, clustering of vacancies is enhanced by the higher mobility of the vacancies along the compressive strain layer.…”

“…[19][20][21] Accumulation of interstitials within the compressively in-plane-strained SiGe layer is mediated primarily by vacancies diffusing towards the strained layer. 20 Furthermore, clustering of vacancies is enhanced by the higher mobility of the vacancies along the compressive strain layer. 22 High resolution electron microscopy of electron irradiated strained Si has shown preferential aggregation of vacancies on ͑001͒ planes within the SiGe layer.…”