• Electronic Properties and Structure of Boron–Hydrogen Complexes in Crystalline Silicon

      De Guzman, Joyce Ann T.; orcid: 0000-0001-5306-5033; email: joyceann.deguzman@manchester.ac.uk; Markevich, Vladimir P.; Coutinho, José; Abrosimov, Nikolay V.; Halsall, Matthew P.; Peaker, Anthony R. (2021-09-17)
      The subject of hydrogen–boron interactions in crystalline silicon is revisited with reference to light and elevated temperature‐induced degradation (LeTID) in boron‐doped solar silicon. Ab initio modeling of structure, binding energy, and electronic properties of complexes incorporating a substitutional boron and one or two hydrogen atoms is performed. From the calculations, it is confirmed that a BH pair is electrically inert. It is found that boron can bind two H atoms. The resulting BH2 complex is a donor with a transition level estimated at E c–0.24 eV. Experimentally, the electrically active defects in n‐type Czochralski‐grown Si crystals co‐doped with phosphorus and boron, into which hydrogen is introduced by different methods, are investigated using junction capacitance techniques. In the deep‐level transient spectroscopy (DLTS) spectra of hydrogenated Si:P + B crystals subjected to heat‐treatments at 100 °C under reverse bias, an electron emission signal with an activation energy of ≈0.175 eV is detected. The trap is a donor with electronic properties close to those predicted for boron–dihydrogen. The donor character of BH2 suggests that it can be a very efficient recombination center of minority carriers in B‐doped p‐type Si crystals. A sequence of boron–hydrogen reactions, which can be related to the LeTID effect in Si:B is proposed.
    • Indium‐Doped Silicon for Solar Cells—Light‐Induced Degradation and Deep‐Level Traps

      De Guzman, Joyce Ann T.; orcid: 0000-0001-5306-5033; email: joyceann.deguzman@manchester.ac.uk; Markevich, Vladimir P.; Hawkins, Ian D.; Ayedh, Hussein M.; Coutinho, José; Binns, Jeff; Falster, Robert; Abrosimov, Nikolay V.; Crowe, Iain F.; Halsall, Matthew P.; et al. (2021-07-21)
      Indium‐doped silicon is considered a possible p‐type material for solar cells to avoid light‐induced degradation (LID), which occurs in cells made from boron‐doped Czochralski (Cz) silicon. Herein, the defect reactions associated with indium‐related LID are examined and a deep donor is detected, which is attributed to a negative‐U defect believed to be InsO2. In the presence of minority carriers or above bandgap light, the deep donor transforms to a shallow acceptor. An analogous transformation in boron‐doped material is related to the BsO2 defect that is a precursor of the center responsible for BO LID. The electronic properties of InsO2 are determined and compared to those of the BsO2 defect. Structures of the BsO2 and InsO2 defects in different charges states are found using first‐principles modeling. The results of the modeling can explain both the similarities and the differences between the BsO2 and InsO2 properties.