TY - JOUR

T1 - Paving the way to dislocation reduction in Ge/Si(001) heteroepitaxy using C-based strained layer superlattices

AU - Barnscheidt, Yvo

AU - Franck, M.

AU - Osten, Hans-Jörg

N1 - Funding information: This work was supported by the Deutsche Forschungsgemeinschaft (DFG) as part of the CMGe-project (Project No. 389061803).

PY - 2020/9/7

Y1 - 2020/9/7

N2 - Epitaxial Ge films were grown on Si(001) substrates by molecular beam epitaxy. During epitaxial growth, two carbon interlayers were deposited at varying substrate temperatures (140-620 ° C) and with varying C quantity (0-1.5 monolayers). The influence of the second carbon interlayer on in-plane strain was investigated using high-resolution X-ray diffraction and transmission electron microscopy (TEM). All samples exhibited compressive strain, which was attributed to substitutional incorporation of carbon atoms. In-plane strain decreases with increasing substrate temperature during carbon deposition, indicating that enhanced surface mobility of carbon adatoms leads to formation of carbon clusters. This was confirmed by cross-sectional TEM investigations. Variation of C quantity at 180 ° C reveals maximum strain at an intermediate quantity of 0.8 monolayers. Omission of the second C interlayer results in much lower strain, indicating a mismatch between the two Ge layers separated by a C interlayer. This could be used to enforce dislocation filtering following the principle of strained layer superlattices. An upper estimate of 1 × 10-3 was found for the mismatch strain, resulting in a critical thickness for dislocation filtering of h c = 153 nm. A sample just exceeding h c exhibited a clear dislocation reduction effect as shown by TEM.

AB - Epitaxial Ge films were grown on Si(001) substrates by molecular beam epitaxy. During epitaxial growth, two carbon interlayers were deposited at varying substrate temperatures (140-620 ° C) and with varying C quantity (0-1.5 monolayers). The influence of the second carbon interlayer on in-plane strain was investigated using high-resolution X-ray diffraction and transmission electron microscopy (TEM). All samples exhibited compressive strain, which was attributed to substitutional incorporation of carbon atoms. In-plane strain decreases with increasing substrate temperature during carbon deposition, indicating that enhanced surface mobility of carbon adatoms leads to formation of carbon clusters. This was confirmed by cross-sectional TEM investigations. Variation of C quantity at 180 ° C reveals maximum strain at an intermediate quantity of 0.8 monolayers. Omission of the second C interlayer results in much lower strain, indicating a mismatch between the two Ge layers separated by a C interlayer. This could be used to enforce dislocation filtering following the principle of strained layer superlattices. An upper estimate of 1 × 10-3 was found for the mismatch strain, resulting in a critical thickness for dislocation filtering of h c = 153 nm. A sample just exceeding h c exhibited a clear dislocation reduction effect as shown by TEM.

UR - http://www.scopus.com/inward/record.url?scp=85091821180&partnerID=8YFLogxK

U2 - 10.1063/5.0004352

DO - 10.1063/5.0004352

M3 - Article

VL - 128

JO - Journal of Applied Physics

JF - Journal of Applied Physics

SN - 0021-8979

IS - 9

M1 - 095703

ER -