Opto-Electrical Properties of Group IV Alloys: The Inherent Challenges of Processing Hydrogenated Germanium

Thierry de Vrijer*, Bilal Bouazzata, Ashwath Ravichandran, Julian E.C. van Dingen, Paul J. Roelandschap, Koos Roodenburg, Steven J. Roerink, Federica Saitta, Thijs Blackstone, Arno H.M. Smets

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

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In this paper the opto-electrical nature of hydrogenated group IV alloys with optical bandgap energies ranging from 1.0 eV up to 2.3 eV are studied. The fundamental physical principles that determine the relation between the bandgap and the structural characteristics such as material density, elemental composition, void fraction and crystalline phase fraction are revealed. Next, the fundamental physical principles that determine the relation between the bandgap and electrical properties such as the dark conductivity, activation energy, and photoresponse are discussed. The unique wide range of IV valence alloys helps to understand the nature of amorphous (a-) and nanocrystalline (nc-) hydrogenated (:H) germanium films with respect to the intrinsicity, chemical stability, and photoresponse. These insights resulted in the discovery of i) a processing window that results in chemically stable Ge:H films with the lowest reported dark conductivity values down to 4.6·10-4 (Ω ·cm)-1 for chemical vapor deposited Ge:H films, and ii) O, C and Sn alloying approaches to improve the photoresponse and chemical stability of the a/nc-Ge:H alloys.

Original languageEnglish
Article number2200814
Number of pages10
JournalAdvanced Science
Issue number18
Publication statusPublished - 2022


  • chemical stability
  • germanium tin GeSn
  • group IV alloys
  • hydrogenated germanium Ge:H
  • plasma enhanced chemical vapor deposition

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