Giant traps on the surface of hydride vapor phase epitaxy-grown free-standing GaN |
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| Authors: | Z -Q Fang D C Look A Krtschil A Krost F A Khan I Adesida |
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| Affiliation: | (1) Semiconductor Research Center, Wright State University, 45435 Dayton, OH;(2) Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson AFB, 45433, OH;(3) Institute of Experimental Physics, Otto-von-Guericke-University Magdeburg, 39016 Magdeburg, Germany;(4) Micro and Nanotechnology Laboratory and Department of Electrical and Computer Engineering, University of Illinois, 61801 Urbana, IL |
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| Abstract: | Extended defects on the top surface of a 250-μm-thick free-standing GaN sample, grown by hydride vapor phase epitaxy (HVPE),
were studied by deep level transient spectroscopy (DLTS) and scanning surface potential microscopy (SSPM). For comparison,
similar studies were carried out on as-grown HVPE-GaN samples. In addition to the commonly observed traps in as-grown HVPE-GaN,
the DLTS measurements on free-standing GaN reveal a very high concentration of deep traps (∼1.0 eV) within about 300 nm of
the surface. These traps show nonexponential capture kinetics, reminiscent of those associated with large defects, that can
accumulate multiple charges. The SSPM measurements clearly reveal the presence of charged microcracks on the top surface of
the sample. It appears that the “giant traps” may be associated with these microcracks, but we cannot rule out the involvement
of other extended defects associated with the near-surface damage caused by the polishing/etching procedure. |
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| Keywords: | Free-standing GaN surface “ giant traps” microcracks deep level transient spectroscopy scanning surface potential microscopy |
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