h1

% IMPORTANT: The following is UTF-8 encoded.  This means that in the presence
% of non-ASCII characters, it will not work with BibTeX 0.99 or older.
% Instead, you should use an up-to-date BibTeX implementation like “bibtex8” or
% “biber”.

@PHDTHESIS{Behmenburg:210483,
      author       = {Behmenburg, Hannes},
      othercontributors = {Heuken, Michael},
      title        = {{C}omprehensive study on {MOVPE} of {I}n{A}l{N}/{G}a{N}
                      {HEMT} structures and {G}a{N} nanowires},
      address      = {Aachen},
      publisher    = {Publikationsserver der RWTH Aachen University},
      reportid     = {RWTH-CONV-143614},
      pages        = {V, 155 S. : Ill., graph. Darst.},
      year         = {2013},
      note         = {Aachen, Techn. Hochsch., Diss., 2013},
      abstract     = {The use of InAlN as barrier layer material is considered as
                      promising idea to enhance the high frequency performance of
                      GaN-based High Electron Mobility Transistors (HEMT). In
                      comparison to the conventionally employed AlGaN, the
                      introduction InAlN allows the realization of a strain free
                      layer stack with enhanced carrier density in the
                      2-dimensional electron gas at simultaneously reduced barrier
                      layer thickness. The reduction of the barrier layer
                      thickness allows to realize short gate lengths and to
                      maintain a high aspect ratio of barrier layer thickness and
                      gate length. This is necessary to ensure control over
                      carriers in the transistor channel. Aim of this work is a
                      comprehensive study of the entire growth process of
                      InAlN/GaN HEMT structures on sapphire and SiC by
                      metalorganic vaporphase epitaxy (MOVPE). First, the
                      development of a GaN buffer structure on sapphire and SiC
                      suitable for high frequency operation is in the focus to
                      allow meaningful evaluation of improvement by introduction
                      of InAlN as new barrier layer material. Necessary properties
                      of this buffer are insulating behavior, a large breakdown
                      field, a low dislocation density and a low background
                      impurity level. It can be shown that the polar orientation
                      of the on sapphire employed AlN nucleation mainly depends on
                      the ratio of initially supplied precursors. Control of the
                      initial supply can be influenced by AlN residues in the
                      reactor chamber. Investigations of the AlN growth conditions
                      show that the development of tensile and compressive strain
                      depends on the V/III ratio employed. This is attributed to a
                      variation of the surface diffusion length of the Al adatom
                      and the associated growth mode. Sequential combination of
                      different V/III ratios can be used to control the state of
                      strain and the surface morphology allowing to deposit 500 nm
                      thick and crack-free AlN layers with a smooth surface. GaN
                      buffer structures deposited on the optimized AlN layer show
                      the required insulating properties, a large breakdown field,
                      a low dislocation density and a low impurity background
                      level. Investigations of the InAlN growth process show an
                      almost linear growth temperature dependency of In
                      incorporation. This allows accurate control of composition
                      and growth lattice matched to the GaN buffer. Unintentional
                      Ga incorporation in InAlN is detected and attributed to GaN
                      residues in the growth reactor. Modifications of the reactor
                      chamber almost completely eliminate the unintentional
                      incorporation of Ga in InAlN. Electrical characterization of
                      processed transistor structures yield excellent power
                      densities of 2,9 W/mm and 2,0 W/mm at 18 GHz and 40 Ghz,
                      respectively. Finally, the catalyst-assisted growth of GaN
                      nanowires on sapphire is investigated for the development of
                      future nanostructured devices. A process window is
                      described, which promotes the growth of 1-dimensional
                      structures leading to the formation of straight,
                      dislocation-free and N-polar nanowires with a diameter of 60
                      nm and a density of 3·109 cm-2. It can be shown that the
                      diameter of the nanowires is influenced by the diameter of
                      the catalyst the size of which is adjustable by the partial
                      pressure of the precursor material.},
      keywords     = {Drei-Fünf-Halbleiter (SWD) / Galliumnitrid (SWD) / HEMT
                      (SWD) / MOCVD-Verfahren (SWD)},
      cin          = {612020},
      ddc          = {620},
      cid          = {$I:(DE-82)612020_20140620$},
      shelfmark    = {85.30.Tv * 81.15.Kk * 73.61.Ey * 73.40.Kp * 68.55.-a *
                      61.05.cp},
      typ          = {PUB:(DE-HGF)11},
      urn          = {urn:nbn:de:hbz:82-opus-45422},
      url          = {https://publications.rwth-aachen.de/record/210483},
}