Interactions of hydrogen atoms with boron and gallium in silicon crystals co-doped with phosphorus and acceptors

Tarek O. Abdul Fattah, Vladimir P. Markevich, Diana Gomes, José Coutinho, Nikolay V. Abrosimov, Ian D. Hawkins, Matthew P. Halsall, Anthony R. Peaker

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Reports showing that hydrogen and group-III acceptors play an important role in Light- and elevated Temperature-induced Degradation (LeTID) of Si-based solar cells highlight the need for a better understanding of interactions between these two species. In this contribution, a combination of junction spectroscopy techniques and first principles modelling has been used to study hydrogen-induced changes in electrical properties of either boron or gallium Czochralski-grown silicon co-doped with phosphorus in order to produce n-type material facilitating novel techniques to assess recombination active defects. The interactions of hydrogen with acceptor atoms have been induced via annealing of these co-doped hydrogenated samples with the application of reverse bias (RBA). These treatments have resulted in a significant increase in the net shallow donor concentration in depletion regions of both materials and in the appearance of a strong electron emission signal due to a trap with an energy level at about E c −0.18 eV in the DLTS spectra of Si:P + B material. It is argued that this trap is related to the donor level of a BH 2 complex. Calculations using density functional theory have shown that the BH 2 defect has a charge-state dependent geometry, which turns out to be crucial for the proposed non-radiative recombination mechanism. The BH 2 defect is therefore suggested to be the root cause of LeTID in boron-doped Si. In contrast, modelling results predict that GaH 2 is a defect with shallow energy levels, without the characteristic features of a recombination centre. This is corroborated by the results of electrical measurements on hydrogenated Si:P + Ga subjected to RBA. Conventional annealing treatments were subsequently used to assess the thermal stability of acceptor-H related defects. Based on the obtained results, the peculiarities of hydrogen interactions with boron and gallium acceptors are discussed.

Original languageEnglish
Article number112447
JournalSolar Energy Materials and Solar Cells
Early online date30 Jun 2023
Publication statusPublished - 15 Aug 2023


  • Acceptor-hydrogen interaction
  • DLTS
  • Hydrogen
  • LeTID
  • Lifetime degradation
  • Silicon solar cells


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