Measurement of induced surface charges, contact potentials, and surface states in GaN by electric force microscopy

We have studied molecular beam epitaxy grown GaN films of both polarities using electric force microscopy to detect sub 1 µm regions of charge density variations associated with GaN extended defects. The large piezoelectric coefficients of GaN together with strain introduced by crystalline imperfections produce variations in piezoelectrically induced electric fields around these defects. The consequent spatial rearrangement of charges can be detected by electrostatic force microscopy and was found to be on the order of the characteristic Debye length for GaN at our dopant concentration. The electric force microscope signal was also found to be a linear function of the contact potential between the metal coating on the tip and GaN. Electrostatic analysis yielded a surface state density of 9.4 ± 0.5 × 10^10 cm – 2 at an energy of 30 mV above the valence band indicating that the GaN surface is unpinned in this case.

[1]  Shuji Nakamura,et al.  Room-temperature continuous-wave operation of InGaN multi-quantum-well structure laser diodes with a lifetime of 27 hours , 1997 .

[2]  M. Seelmann-Eggebert,et al.  Polarity of (00.1) GaN epilayers grown on a (00.1) sapphire , 1997 .

[3]  Nitride based high power devices: design and fabrication issues , 1998 .

[4]  T. Moustakas,et al.  Photoemission study of the electronic structure of wurtzite GaN(0001) surfaces , 1997 .

[5]  H. J. Hagger,et al.  Solid State Electronics , 1960, Nature.

[6]  Michael S. Shur,et al.  The influence of the strain‐induced electric field on the charge distribution in GaN‐AlN‐GaN structure , 1993 .

[7]  B. Terris,et al.  Imaging of ferroelectric domain walls by force microscopy , 1990 .

[8]  M. Shur,et al.  GaN based transistors for high temperature applications , 1997 .

[9]  Hadis Morkoç,et al.  Progress and prospects of group-III nitride semiconductors , 1996 .

[10]  S. M. Sze,et al.  Physics of semiconductor devices , 1969 .

[11]  Jinghua Guo,et al.  Bulk and Surface Electronic Structure of GaN Measured Using Angle-Resolved Photoemission, Soft X-ray Emission and Soft X-ray Absorption , 1996 .

[12]  T. C. Mcgill,et al.  Growth of Iii-Nitrides by Rf-Assisted Molecular Beam Epitaxy , 1998 .

[13]  A. Broniatowski,et al.  A high-resolution scanning Kelvin probe microscope for contact potential measurements on the 100 nm scale , 1997 .

[14]  P. Vogl,et al.  Prospects of Ga/In/Al–N Nanometer Devices: Electronic Structure, Scattering Rates, and High Field Transport , 1997 .

[15]  E. Rhoderick,et al.  Solid State Electronics , 1970 .

[16]  Peter M. Asbeck,et al.  Measurement of piezoelectrically induced charge in GaN/AlGaN heterostructure field-effect transistors , 1997 .

[17]  T. C. Mcgill,et al.  Fermi-level position at a semiconductor-metal interface , 1983 .

[18]  Peter P. Chow,et al.  Ultraviolet-sensitive, visible-blind GaN photodiodes fabricated by molecular beam epitaxy , 1997 .

[19]  D. Greve,et al.  Determination of wurtzite GaN lattice polarity based on surface reconstruction , 1998 .

[20]  S. Lau,et al.  A review of the metal–GaN contact technology , 1998 .

[21]  H. Kumar Wickramasinghe,et al.  High‐resolution capacitance measurement and potentiometry by force microscopy , 1988 .

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