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@INPROCEEDINGS{Kovcs:827178,
      author       = {Kovács, András and Duchamp, Martial and Predan, Felix and
                      Dimroth, Frank and Dunin-Borkowski, Rafal and Jäger,
                      Wolfgang},
      title        = {{A}tomic resolution {HR}({S}){TEM} and {EDXS} analyses of
                      {G}a{I}n{A}s/{G}a{S}b and {G}a{I}n{P}/{G}a{S}b bond
                      interfaces for high-efficiency solar cells},
      address      = {Weinheim, Germany},
      publisher    = {Wiley-VCH Verlag GmbH $\&$ Co. KGaA},
      reportid     = {FZJ-2017-01376},
      pages        = {846 - 847},
      year         = {2016},
      comment      = {European Microscopy Congress 2016: Proceedings},
      booktitle     = {European Microscopy Congress 2016:
                       Proceedings},
      abstract     = {The use of direct wafer bonding to combine semiconductor
                      materials that have a large lattice mismatch is especially
                      beneficial for high efficiency multi-junction solar cells.
                      Multi-junction solar cells that have been fabricated by
                      wafer bonding are of particular interest since efficiencies
                      of up to $46\%$ have been obtained [1] and efficiencies of
                      up to $50\%$ are within reach for concentrator solar cells
                      based on III-V compound semiconductors. Fast atom beam
                      activation is used as a pre-treatment to remove oxides and
                      contamination before bonding [2]. Aberration-corrected
                      transmission electron microsocpy (TEM) analyses of GaAs/Si
                      interfaces have previously been applied successfully to
                      support the implementation of bonding concepts for the
                      development of high-efficiency solar cells [3].Here, we
                      investigate cross-sectional specimens of GaInAs/GaSb and
                      GaInP/GaSb bond interfaces in wafer-bonded multi-junction
                      solar cells, in order to obtain an improved understanding of
                      their interface structures and thermal stability, by
                      combining aberration-corrected high-resolution TEM (HRTEM),
                      high-angle annular dark-field scanning TEM (HAADF STEM),
                      energy-dispersive X-ray spectroscopy (EDXS) in the STEM and
                      in situ TEM heating experiments.Figures 1a-e shows results
                      obtained from the GaInP/GaSb bond interface. Fig.1a shows
                      the interface at low magnification. Figure 1b shows an HRTEM
                      image, which reveals an amorphous interface layer (~1 nm
                      thick). Figure 1c shows an atomic resolution HAADF STEM
                      image of the bond interface structure and a digital
                      diffractogram (inset), revealing a nearly perfect structural
                      orientation relationship between the two crystalline layers.
                      When correctly positioned with respect to the HAADF image,
                      elemental maps extracted from EDXS spectrum images (Figs 1d
                      and 1e) reveal that a high level of Ga is present at the
                      interface. The Ga can be attributed to the pre-treatment
                      procedure and bonding conditions.I situ thermal treatment of
                      this interface results in pronounced interdiffusion for
                      temperatures above 225°C (not shown here).Figures 2a-c show
                      the GaInAs/GaSb bond interface, which is decorated by pores
                      and cavities that extend along the interface by more than 10
                      nm. As a result of the use of misoriented wafers for
                      bonding, the crystal lattices are rotated with respect to
                      each other by a few degrees (Figs 2b and 2c).Our results
                      confirm that the advanced imaging and spectroscopic methods
                      of aberration-corrected (S)TEM are advantageous for
                      characterizing the morphology, elemental distribution and
                      structure of layers and bond interfaces for the monitoring,
                      control and optimization of different concepts used for
                      fabricating high-efficiency solar cells. Out results are
                      also of interest for assessing electrical conductivity
                      phenomena at these interfaces.},
      month         = {Aug},
      date          = {2016-08-28},
      organization  = {16th European Microscopy Congress,
                       Lyon (France), 28 Aug 2016 - 2 Sep
                       2016},
      cin          = {PGI-5 / ER-C-1},
      cid          = {I:(DE-Juel1)PGI-5-20110106 / I:(DE-Juel1)ER-C-1-20170209},
      pnm          = {143 - Controlling Configuration-Based Phenomena (POF3-143)},
      pid          = {G:(DE-HGF)POF3-143},
      typ          = {PUB:(DE-HGF)8 / PUB:(DE-HGF)7},
      doi          = {10.1002/9783527808465.EMC2016.6029},
      url          = {https://juser.fz-juelich.de/record/827178},
}