Nonselective etching of As and P based III‒V solar cell heterostructures with aqueous solutions of HIO3 and HCl
Raappana, Marianna; Koikkalainen, Tomi; Polojärvi, Ville; Aho, Arto; Aho, Timo; Isoaho, Riku; Tukiainen, Antti; Guina, Mircea (2021-07-01)
Raappana, Marianna
Koikkalainen, Tomi
Polojärvi, Ville
Aho, Arto
Aho, Timo
Isoaho, Riku
Tukiainen, Antti
Guina, Mircea
01.07.2021
111097
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tuni-202104284062
https://urn.fi/URN:NBN:fi:tuni-202104284062
Kuvaus
Peer reviewed
Tiivistelmä
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.
Kokoelmat
- TUNICRIS-julkaisut [16929]