A1 Refereed original research article in a scientific journal

Challenges in Simultaneous Microstructuring and Hyperdoping of Germanium with Ultrafast Laser




AuthorsGnatyuk, Dmytro; Hamed, Sara; Ebrahimzadeh, Masoud; Liu, Hanchen; Vahanissi, Ville; Laukkanen, Pekka; Savin, Hele; Liu, Xiaolong

PublisherWiley

Publication year2026

Journal: physica status solidi (a)

Article numbere202500987

Volume223

Issue8

ISSN1862-6300

eISSN1862-6319

DOIhttps://doi.org/10.1002/pssa.202500987

Publication's open availability at the time of reportingOpen Access

Publication channel's open availability Partially Open Access publication channel

Web address https://doi.org/10.1002/pssa.202500987

Self-archived copy’s web addresshttps://research.utu.fi/converis/portal/detail/Publication/523237968

Self-archived copy's licenceCC BY

Self-archived copy's versionPublisher`s PDF


Abstract

Germanium's compatibility with Complementary Metal-Oxide-Semiconductor (CMOS) and strong near-infrared response make it an attractive platform for infrared photonics, but its intrinsic material properties hinder straightforward extension of absorption beyond the band edge. In this perspective, we synthesize recent and new experiments and analyses on femtosecond-laser approaches that attempt to combine surface microstructuring and hyperdoping of Ge in a single step. We argue that, unlike silicon, Ge's high optical absorption at visible/green wavelengths, shallow energy deposition, lower melting point, and reduced thermal conductivity favor intense localized heating, evaporation, and redeposition-conditions that both produce high baseline sub-bandgap absorption from damage and prevent effective incorporation of thin-film dopant precursors. In a case example, Ti shows only trace incorporation from qualitative measurements. We discuss why laser-induced structural disorder, rather than stable deep dopant incorporation, dominates the optical response, and we outline practical pathways forward: exploring longer wavelengths or gas-phase chemistries, applying separate in situ heating, or decoupling texturing from heavy doping.


Downloadable publication

This is an electronic reprint of the original article.
This reprint may differ from the original in pagination and typographic detail. Please cite the original version.




Funding information in the publication
This study was supported by Research Council of Finland through project HyperGer (354199), NIR-REM (365427), and PREIN (346529).


Last updated on 08/05/2026 09:28:54 AM