Distinguishing negatively-charged and highly conductive dislocations in gallium nitride using scanning Kelvin probe and conductive atomic force microscopy

Scanning Kelvin probe microscopy (SKPM) and conductive atomic force microscopy (C-AFM) are used to image surfaces of GaN grown by molecular beam epitaxy (MBE). Numerical simulations are used to assist in the interpretation of SKPM images. Detailed analysis of the same area using both techniques allows imaging of surface potential variations arising from the presence of negatively charged dislocations and dislocation-related current leakage paths. Correlations between the charge state of dislocations, conductivity of leakage current paths, and possibly dislocation type can thereby be established. Approximately 25% of the leakage paths appear to be spatially correlated with negatively charged dislocation features. This is approximately the level of correlation expected due to spatial overlap of randomly distributed, distinct features of the size observed, suggesting that the negatively charged dislocations are distinct from those responsible for localized leakage paths found in GaN. The effects of charged dislocation networks on the local potential profile is modeled and discussed.

[1]  James S. Speck,et al.  Control of GaN surface morphologies using plasma-assisted molecular beam epitaxy , 2000 .

[2]  Y.-F. Wu,et al.  High Al-content AlGaN/GaN MODFETs for ultrahigh performance , 1998, IEEE Electron Device Letters.

[3]  Sven Öberg,et al.  DEEP ACCEPTORS TRAPPED AT THREADING-EDGE DISLOCATIONS IN GAN , 1998 .

[4]  X. H. Wu,et al.  Dislocation generation in GaN heteroepitaxy , 1998 .

[5]  Andreas Stemmer,et al.  Surface potential mapping: A qualitative material contrast in SPM , 1997 .

[6]  D. Lang,et al.  Surface morphology and electronic properties of dislocations in AlGaN/GaN heterostructures , 2001 .

[7]  James S. Speck,et al.  Defect structure of metal‐organic chemical vapor deposition‐grown epitaxial (0001) GaN/Al2O3 , 1996 .

[8]  Julia W. P. Hsu,et al.  Scanning Kelvin force microscopy imaging of surface potential variations near threading dislocations in GaN , 2002 .

[9]  E. Yu,et al.  Lateral variations in threshold voltage of an AlxGa1−xN/GaN heterostructure field-effect transistor measured by scanning capacitance spectroscopy , 2001 .

[10]  Satoshi Kurai,et al.  Direct Evidence that Dislocations are Non-Radiative Recombination Centers in GaN , 1998 .

[11]  A. Stemmer,et al.  Investigation of the cleaved surface of a p–i–n laser using Kelvin probe force microscopy and two-dimensional physical simulations , 2000 .

[12]  H. K. Wickramasinghe,et al.  Kelvin probe force microscopy , 1991 .

[13]  Richard J. Molnar,et al.  Scanning Kelvin probe microscopy of surface electronic structure in GaN grown by hydride vapor phase epitaxy , 2002 .

[14]  Christiane Poblenz,et al.  Reduction of reverse-bias leakage current in Schottky diodes on GaN grown by molecular-beam epitaxy using surface modification with an atomic force microscope , 2002 .

[15]  Ulrike Grossner,et al.  The effect of doping and growth stoichiometry on the core structure of a threading edge dislocation in GaN , 1998 .

[16]  James S. Speck,et al.  Direct imaging of reverse-bias leakage through pure screw dislocations in GaN films grown by molecular beam epitaxy on GaN templates , 2002 .

[17]  Lester F. Eastman,et al.  The role of dislocation scattering in n-type GaN films , 1998 .

[18]  James S. Speck,et al.  Scanning capacitance microscopy imaging of threading dislocations in GaN films grown on (0001) sapphire by metalorganic chemical vapor deposition , 1998 .

[19]  Michael G. Spencer,et al.  Scanning Kelvin probe microscopy characterization of dislocations in III-nitrides grown by metalorganic chemical vapor deposition , 2001 .

[20]  S. Nakamura,et al.  InGaN-Based Multi-Quantum-Well-Structure Laser Diodes , 1996 .

[21]  M. Asif Khan,et al.  Growth defects in GaN films on sapphire: The probable origin of threading dislocations , 1996 .