Einfluss der freien Ladungsträgerdichte auf die Kernstruktur und die elektronischen Eigenschaften von Versetzungen in Galliumnitrid

• Antragsteller: Professor Dr. Michael Seibt
• Fachliche Zuordnung: Experimentelle Physik der kondensierten Materie ; Herstellung und Eigenschaften von Funktionsmaterialien
• Förderung: Förderung von 2017 bis 2021
• Projektkennung: Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 323634749

• Erstellungsjahr: 2021

Zusammenfassung der Projektergebnisse

Dislocation related luminescence (DRL) is a phenomenon frequently observed in semiconductors after deformation. Besides the classical example of DRL associated with photoluminescence (PL) signals D1 to D4 in silicon discovered 1970s, the recently observed sub-bandgap luminescence related to freshly introduced a-screw dislocations in GaN has drawn some attention during the last five years. Open questions at the beginning of the project included the structural origin of the observed DRL. The joint project with O. Vyvenko’s group at St. Petersburg State University (SPbU) tried to combine spectral investigations (PL and cathodoluminescence, CL) with structural analysis using various techniques of (scanning) transmission electron microscopy ((S)TEM). Since these experimental techniques have to be applied to the same defects, a combination of electron beam induced current (EBIC) and focused ion beam (FIB), have been used to localize dislocations and subsequently perform a site-specific TEM sample preparation. This technique is available in our group and has been further developed within this project. In combined spectroscopic and structural investigations, a plausible model for the DRL has been developed. According to this model, the freshly introduced a-screw dislocations are dissociated into partial dislocations bounding a stacking fault ribbon with a local cubic stacking of atomic planes. As a result, a quantum well-like structure consisting of monoatomic cubic GaN (energy gap: 3.2 eV) sandwiched between wurtzite GaN (energy gap: 3.4 eV) forms. High-resolution TEM studies of the dislocation core structure turned out to be virtually impossible due to the high electron irradiation-induced mobility of the a-screw dislocations. As a consequence, we implemented two approaches operating at lower electron beam currents, i.e. (i) conventional dark field imaging under weak-beam conditions to observe stacking fault fringes from inclined dislocations, and (ii) 4D-STEM investigations in plan view geometry. The latter required a novel site-specific plan view TEM lamella preparation procedure devised and implemented in this project. Both techniques consistently show that freshly produced a-screw dislocations are indeed dissociated, which again corroborates the developed microscopic model of DRL in GaN. The 4D-STEM technique needs further quantification by means of STEM image simulations and should be also applicable to study the structure of dislocation nodes and intersections, which have recently been identified as PL-active sites by our collaborators at SPbU.

Projektbezogene Publikationen (Auswahl)

• Intrinsic luminescence and core structure of freshly introduced a-screw dislocations in n-GaN, Journal of Applied Physics, 123 (2018), p. 161427
  O. Medvedev, O. Vyvenko, E. Ubyivovk, S. Shapenkov, A. Bondarenko,P. Saring, and M. Seibt
  
• Structural modifications in free-standing InGaN/GaN LEDs after femtosecond laser lift-off, Proceedings, 2 (2018)
  S. Bornemann, N. Yulianto, T. Meyer, J. Gülink, C. Margenfeld, M. Seibt, H. S. Wasisto, and A. Waag
  
• Correlation of structure and intrinsic luminescence of freshly introduced dislocations in GaN revealed by SEM and TEM, AIP Conference Proceedings, 2064(2019), p. 040003
  O. S. Medvedev, O. F. Vyvenko, E. V. Ubyivovk, S. V. Shapenkov, and M. Seibt
  
• Extended core structure and luminescence of a-screw dislocations in GaN, Journal of Physics: Conference Series, 1009 (2019), p. 012006
  O. S. Medvedev, O. F. Vyvenko, E. V. Ubyivovk, S. V. Shapenkov and M Seibt
  
• Defect reaction paths of nickel in float zone silicon controlled by non equilibrium vacancies, Dissertation, Göttingen University 2020
  P. Saring
  
• Plasma profiling time-of-flight mass spectrometry for fast elemental analysis of semiconductor structures with depth resolution in the nanometer range, Semiconductor Science and Technology, 35 (2020), p. 035006
  H. Spende, C. Margenfeld, T. Meyer, I. M. Clavero, H. Bremers,A. Hangleiter, M. Seibt, A. Waag, and A. Bakin
  
• Recombination and charge collection at nickel silicide precipitates in silicon studied by electron beam-induced current, Physica Status Solidi (B) 258(10) (2021), p. 2100142
  P. Saring and M. Seibt
  
• Site-specific plan-view TEM lamella preparation of pristine surfaces with a large field of view, Ultramicroscopy, 228 (2021), p. 113320
  T. Meyer, T. Westphal, B. Kressdorf, U. Ross, C. Jooss, and M. Seibt