From plastic to elastic stress relaxation in highly mismatched SiGe/Si heterostructures

Research output: Contribution to journalResearch articleContributedpeer-review

Contributors

  • Fabio Isa - , Swiss Federal Laboratories for Materials Science and Technology (Empa) (Author)
  • Marco Salvalaglio - , University of Milan - Bicocca, TUD Dresden University of Technology (Author)
  • Yadira Arroyo Rojas Dasilva - , Swiss Federal Laboratories for Materials Science and Technology (Empa) (Author)
  • Arik Jung - , Swiss Federal Laboratories for Materials Science and Technology (Empa) (Author)
  • Giovanni Isella - , Polytechnic University of Milan (Author)
  • Rolf Erni - , Swiss Federal Laboratories for Materials Science and Technology (Empa) (Author)
  • Philippe Niedermann - , Swiss Center for Electronics and Microtechnology (CSEM) (Author)
  • Pierangelo Groning - , Swiss Federal Laboratories for Materials Science and Technology (Empa) (Author)
  • Francesco Montalenti - , University of Milan - Bicocca (Author)
  • Hans von Kanel - , Swiss Federal Laboratories for Materials Science and Technology (Empa) (Author)

Abstract

We present a detailed experimental and theoretical analysis of the epitaxial stress relaxation process in micro-structured compositionally graded alloys. We focus on the pivotal SiGe/Si(001) system employing patterned Si substrates at the micrometre-size scale to address the distribution of threading and misfit dislocations within the heterostructures. SiGe alloys with linearly increasing Ge content were deposited by low energy plasma enhanced chemical vapour deposition resulting in isolated, tens of micrometre tall 3D crystals. We demonstrate that complete elastic relaxation is achieved by appropriate choice of the Ge compositional grading rate and Si pillar width. We investigate the nature and distribution of dislocations along the [001] growth direction in SiGe crystals by transmission electron microscopy, chemical defect etching and etch pit counting. We show that for 3 gm wide Si pillars and a Ge grading rate of 1.5% mu m(-1), only misfit dislocations are present while their fraction is reduced for higher Ge grading rates and larger structures due to dislocation interactions. The experimental results are interpreted with the help of theoretical calculations based on linear elasticity theory describing the competition between purely elastic and plastic stress relaxation with increasing crystal width and Ge compositional grading rate. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Details

Original languageEnglish
Pages (from-to)97-105
Number of pages9
JournalActa materialia
Volume114
Publication statusPublished - 1 Aug 2016
Peer-reviewedYes
Externally publishedYes

External IDs

Scopus 84990909775
ORCID /0000-0002-4217-0951/work/142237432

Keywords

Keywords

  • Graded buffer, Elastic relaxation, Dislocations, Epitaxy, SiGe, THREADING DISLOCATION DENSITIES, STRAIN, SI, EPITAXY, SILICON, GE, HETEROEPITAXY, REDUCTION, THICKNESS, GROWTH