Nonselective etching of As and P based III‒V solar cell heterostructures with aqueous solutions of HIO3 and HCl

Marianna Raappana, Tomi Koikkalainen, Ville Polojärvi, Arto Aho, Timo Aho, Riku Isoaho, Antti Tukiainen, Mircea Guina

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Etching characteristics of lattice-matched GaInP/GaAs/GaInNAsSb heterostructures by aqueous solutions of iodic acid (HIO3) and hydrochloric acid (HCl) is reported. The study aims at optimization of mesa fabrication process involved in the development of III‒V multijunction solar cells. The effects of temperature, agitation, etchant composition, and illumination on the etching selectivity are investigated. Varying the etchant composition and agitation rate at room temperature results in various mesa sidewall morphologies, ranging from rough surfaces and significant undercut to smoother sidewall profiles with only minor undercut. Especially, the undercut emerging in the GaInNAsSb junction, as well as in the AlInP layers, was observed for several etching conditions. Increasing the etching temperature also caused an unwanted increase in the selectivity, whereas reducing the temperature below the room temperature enhanced remarkably the formation of smooth morphology. Illumination during the etching resulted in a severe undercut in the GaAs junction, due to an increased selectivity caused by photoetching. This points out the need of controlled illumination condition to avoid unwanted reactions in wet etching of such multijunction structures. The etching process resulting in the best morphology was used for electrical isolation of triple-junction GaInP/GaAs/GaInNAsSb solar cells. The good photovoltaic performance exhibited by these devices proves the suitability of the nonselective etch process in developing multijunction solar cells.

Original languageEnglish
Article number111097
Number of pages7
JournalSolar Energy Materials and Solar Cells
Publication statusPublished - 1 Jul 2021
Publication typeA1 Journal article-refereed


  • Device fabrication
  • III‒V heterostructures
  • Mesa etching
  • Multijunction solar cell
  • Nonselective etchant
  • Wet etching

Publication forum classification

  • Publication forum level 2

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Renewable Energy, Sustainability and the Environment
  • Surfaces, Coatings and Films


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