Control of Sn Precipitation and Strain Relaxation in Compositionally Step-Graded Ge_1-xSn_x Buffer Layers for Tensile-Strained Ge Layers

Abstract

We investigated the relationship between Sn precipitation and strain relaxation in Ge 1Àx Sn x buffer layers grown by the compositionally step-graded (CSG) method on a virtual Ge substrate. We found that the strain in the upper Ge 1Àx Sn x layers is reduced by Sn precipitation rather than the lateral propagation of misfit dislocations at the interfaces of upper Ge 1Àx Sn x layers in the CSG method. The critical misfit strain was increased to 5:8 Â 10 À3 compared with that in our previous work by lowering the temperature of the postdeposition annealing, and a Sn content of 6.3% in the Ge 1Àx Sn x buffer layer was achieved with a large degree of strain relaxation using only two stacked layers of the CSG structure. An in-plane tensile strain of 0.62% in a 30-nm-thick Ge layer fabricated on these Ge 1Àx Sn x buffer layers was achieved. #

Amorphous inclusions during Ge and GeSn epitaxial growth via chemical vapor deposition

“…Low temperature growth processes are often required in order to fabricate Ge or GeSn heterostructures without undesired strain relaxations, elemental intermixing, dopant diffusion or Sn precipitation [5]. However, low-temperature growth is known to have a series of possible undesired consequences, such as the roughening of the surface [6], the formation of defects or the inclusion of localized or extended amorphous regions [6][7][8] (often referred to as epitaxial breakdown).…”

Undoped and in-situ B doped GeSn epitaxial growth on Ge by atmospheric pressure-chemical vapor deposition

“…10,13 Further anneals were then done after growth on the GeSn layers in order to assess their thermal stability. Anneals were performed in a rapid thermal anneal equipment at 400 C and 500 C for 10 and 30 min in pure N 2 .…”

Technology Evolution of Silicon Nano-Electronics

“…As a result, XRD 2dimensional reciprocal space mapping (XRD-2DRSM) observation revealed that a Sn content and a DSR of the top CSG buffer layer achieved to 6.3% and 77%, respectively. A tensile strain value of the Ge layer on this CSG structure achieved to 0.62% for bulk Ge (8).…”

“…In our previous work, we found that there is the critical misfit strain of Sn precipitation (7). Recently, we also reported that the long time and low temperature annealing is effective to increase the critical misfit strain by suppressing Sn precipitation and to realize a high DSR (8). Considering the critical misfit strain of Sn precipitation, we proposed the compositionally step-graded (CSG) Ge 1-x Sn x multilayer structure.…”

“…Long time and low temperature annealing is effective to enhance the propagation of misfit dislocations with suppressing Sn precipitation (8). In addition, the effects of Ge 1-x Sn x layer thickness and low temperature growth are important to enhance the propagation of misfit dislocations.…”