Local Polarization Effects in Nitride Heterostructures and Devices

  • E. T. Yu
  • P. M. Asbeck

As described in the accompanying chapters of this volume, spontaneous and piezoelectric polarization effects play an extremely prominent role in Group III-nitride semiconductors, influencing potential and charge distributions and carrier transport in a broad range of nitride-based semiconductor heterostructure devices. In this chapter we focus on the existence, nature, and consequences of inhomogeneities in polarization fields and polarization charge distributions that arise from factors such as defects, non-uniform strain fields, or nanoscale compositional and layer thickness variations in basic heterostructure materials, as well as from process-induced defects, non-uniform stress due to metallization or etching, and related issues in electronic device structures. Possibilities for the intentional introduction of polarization fields to enhance device performance are also highlighted.


Polarization Charge Gallium Nitride AlGaN Layer Piezoelectric Polarization Nitride Semiconductor 
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  1. 1.
    P. Asbeck, C. P. Lee and M. F. Chang, “Piezoelectric effects in GaAs FETs and their role in orientation dependent device characteristics”, IEEE Trans. on Electron Devices 31, 1377 (1984).CrossRefGoogle Scholar
  2. 2.
    D. L. Smith. Strain-generated electric-fields in [111] growth axis strained-layer superlattices. Solid-State Commun. 57, 919-21 (1986).CrossRefGoogle Scholar
  3. 3.
    D. L. Smith and C. Mailhiot. Piezoelectric effects in strained-layer superlattices. J. Appl. Phys. 63,2717-9 (1988).CrossRefGoogle Scholar
  4. 4.
    T. F. Kuech, R. T. Collins, D. L. Smith, and C. Mailhiot. Field-effect transistor structure based on strain-induced polarization charges. J. Appl. Phys. 67, 2650-2 (1990).CrossRefGoogle Scholar
  5. 5.
    E. S. Snow, B. V. Shanabrook, and D. Gammon. Strain-induced 2-dimensional electron-gas in [111] growth-axis strained-layer structures. Appl. Phys. Lett. 56, 758-60 (1990).CrossRefGoogle Scholar
  6. 6.
    J. F. Nye. Physical Properties of Crystals: Their Representation by Tensors and Matrices(Oxford University Press, Oxford, 1998).Google Scholar
  7. 7.
    S. Strite, M. E. Lin, and H. Morkoç. Progress and prospects for GaN and the III-V-nitride semiconductors. Thin Solid Films 231, 197-210 (1993).CrossRefGoogle Scholar
  8. 8.
    O. Ambacher, J. Majewski, C. Miskys, A. Link, M. Hermann, M. Eickhoff, M. Stutzmann, F. Bernardini, V. Fiorentini, V. Tilak, B. Schaff, and L. F. Eastman. Pyroelectric properties of Al(In)GaN/GaN hetero- and quantum well structures. J. Phys.: Condens. Matter 14, 3399-3434 (2002).CrossRefGoogle Scholar
  9. 9.
    M. A. Littlejohn, J. R. Hauser, and T. H. Glisson. Monte-Carlo calculation of velocity-field relationship for gallium nitride. Appl. Phys. Lett. 26, 625-7 (1975).CrossRefGoogle Scholar
  10. 10.
    A. D. Bykhovski, B. L. Gelmont, and M. S. Shur. Elastic strain relaxation and piezoeffect in GaN-AlN, GaN-AlGaN, and GaN-InGaN superlattices. J. Appl. Phys. 81, 6332-8 (1997).CrossRefGoogle Scholar
  11. 11.
    G. D. O’Clock, Jr. and M. T. Duffy. Acoustic surface-wave properties of epitaxially grown aluminum nitride and gallium nitride on sapphire. Appl. Phys. Lett. 23, 55-6 (1973).CrossRefGoogle Scholar
  12. 12.
    A. D. Bykhovski, V. V. Kaminski, M. S. Shur, Q. C. Chen, and M. A. Khan. Piezoresistive effect in wurtzite n-type GaN. Appl. Phys. Lett. 68, 818-9 (1996).CrossRefGoogle Scholar
  13. 13.
    J. G. Gualtieri, J. A. Kosinski, and A. Ballato. Piezoelectric materials for acoustic-wave applications. IEEE Trans. Ultrason. Ferroelectr. Freq. Control 41, 53-9 (1994).CrossRefGoogle Scholar
  14. 14.
    F. Bernardini, V. Fiorentini, and D. Vanderbilt. Spontaneous polarization and piezoelectric constants of III-V nitrides. Phys. Rev. B 56, R10024-7 (1997).CrossRefGoogle Scholar
  15. 15.
    V. A. Savastenko and A. U. Sheleg. Study of elastic properties of gallium nitride. Phys. Status Solidi A 48, K135-9 (1978).CrossRefGoogle Scholar
  16. 16.
    Y. Takagi, M. Ahart, T. Azuhata, T. Sota, K. Suzuki, and S. Nakamura. Brillouin scattering study in the GaN epitaxial layer. Physica B 219&220, 547-9 (1996).CrossRefGoogle Scholar
  17. 17.
    A. Polian, M. Grimsditch, and I. Grzegory. Elastic constants of gallium nitride. J. Appl. Phys. 79,3343-4 (1996).CrossRefGoogle Scholar
  18. 18.
    R. B. Schwarz, K. Khachaturyan, and E. R. Weber. Elastic moduli of gallium nitride. Appl. Phys. Lett. 70, 1122-4 (1997).CrossRefGoogle Scholar
  19. 19.
    C. Deger, E. Born, H. Angerer, O. Ambacher, M. Stutzmann, J. Hornsteiner, E. Riha, and G. Fischerauer. Sound velocity of AlxGa1− xN thin films obtained by surface acoustic-wave measurements. Appl. Phys. Lett. 72, 2400-2 (1998).CrossRefGoogle Scholar
  20. 20.
    K. Tsubouchi and N. Mikoshiba. Zero-temperature-coefficient SAW devices on AlN epitaxialfilms. IEEE Trans. Sonics Ultrason. SU-32, 634-44 (1985).Google Scholar
  21. 21.
    L. E. McNeil, M. Grimsditch, and R. H. French. Vibrational spectroscopy of aluminum nitride. J. Am. Ceram. Soc. 76, 1132-6 (1993).CrossRefGoogle Scholar
  22. 22.
    K. Kim, W. R. L. Lambrecht, and B. Segall. Elastic constants and related properties of tetrahedrally bonded BN, AlN, GaN, and InN. Phys. Rev. B 53, 16310-26 (1996).CrossRefGoogle Scholar
  23. 23.
    A. F. Wright. Elastic properties of zinc-blende and wurtzite AlN, GaN, and InN. J. Appl. Phys. 82,2833-9 (1997).CrossRefGoogle Scholar
  24. 24.
    S. Chichibu, T. Azuhata, T. Sota, and S. Nakamura. Spontaneous emission of localized excitons in InGaN single and multiquantum well structures. Appl. Phys. Lett. 69, 4188-90 (1996).CrossRefGoogle Scholar
  25. 25.
    S. F. Chichibu, A. C. Abare, M. S. Minsky, S. Keller, S. B. Fleischer, J. E. Bowers, E. Hu, U. K. Mishra, L. A. Coldren, and S. P. DenBaars, and T. Sota. Effective band gap inhomogeneity and piezoelectric field in InGaN/GaN multiquantum well structures. Appl. Phys. Lett. 73, 2006-8 (1998).CrossRefGoogle Scholar
  26. 26.
    T. Takeuchi, C. Wetzel, S. Yamaguchi, H. Sakai, H. Amano, I. Akasaki, Y. Kaneko, S. Nakagawa, Y. Yamaoka, and N. Yamada. Determination of piezoelectric fields in strained GaInN quantum wells using the quantum-confined Stark effect. Appl. Phys. Lett. 73, 1691-3 (1998).CrossRefGoogle Scholar
  27. 27.
    J. A. Garrido, J. L. Sanchez-Rojas, A. Jimenez, E. Munoz, F. Omnes, and P. Gibart. Polarization fields determination in AlGaN/GaN heterostructure field-effect transistors from charge control analysis. Appl. Phys. Lett. 75, 2407-9 (1999).CrossRefGoogle Scholar
  28. 28.
    P. Lefebvre, A. Morel, M. Gallart, T. Taliercio, J. Allegre, B. Gil, H. Mathieu, B. Damilano, N. Grandjean, and J. Massies. High internal electric field in a graded-width InGaN/GaN quantum well: accurate determination by time-resolved photoluminescence spectroscopy. Appl. Phys. Lett. 78, 1252-4 (2001).CrossRefGoogle Scholar
  29. 29.
    Y. D. Jho, J. S. Yahng, E. Oh, and D. S. Kim. Measurement of piezoelectric field and tunneling times in strongly biased InGaN/GaN quantum wells. Appl. Phys. Lett. 79, 1130-2 (2001).CrossRefGoogle Scholar
  30. 30.
    F. Renner, P. Kiesel, and G. H. Dohler, M. Kneissl, C. G. Van de Walle, and N. M. Johnson. Quantitative analysis of the polarization fields and absorption changes in InGaN/GaN quantum wells with electroabsorption spectroscopy. Appl. Phys. Lett. 81, 490-2 (2002).CrossRefGoogle Scholar
  31. 31.
    C. Y. Lai, T. M. Hsu, W.-H. Chang, and K.-U. Tseng. Direct measurement of piezoelectric field in In0.23 Ga0.77 N/GaN multiple quantum wells by electrotransmission spectroscopy. J. Appl. Phys. 91, 531-3 (2002).CrossRefGoogle Scholar
  32. 32.
    E. J. Miller, E. T. Yu, C. Poblenz, C. Elsass, and J. S. Speck. Direct measurement of the polarization charge in AlGaN/GaN heterostructures using capacitance-voltage carrier profiling. Appl. Phys. Lett. 80, 3551-3 (2002).CrossRefGoogle Scholar
  33. 33.
    H. Zhang, E. J. Miller, E. T. Yu, C. Poblenz, and J. S. Speck. Measurement of polarization charge and conduction band offset at InxGa1-xN/GaN heterojunction interfaces. Appl. Phys. Lett. 84, 4644-6 (2004).CrossRefGoogle Scholar
  34. 34.
    E. T. Yu, G. J. Sullivan, P. M. Asbeck, C. D. Wang, D. Qiao, and S. S. Lau. Measurement of piezoelectrically induced charge in GaN/AlGaN heterostructure field-effect transistors. Appl. Phys. Lett. 71, 2794-6 (1997).CrossRefGoogle Scholar
  35. 35.
    R. People, K. W. Wecht, K. Alavi, and A. Y. Cho. Measurement of the conduction-band discontinuity of molecular-beam epitaxial grown In0.52 Al0.48 As/In0.53 Ga0.47 As n-n heterojunction by C-V profiling. Appl. Phys. Lett. 43, 118-20 (1983).CrossRefGoogle Scholar
  36. 36.
    H. Kroemer, Wu-Yi Chien, J. S. Harris, Jr., and D. D. Edwall. Measurement of isotype heterojunction barriers by C-V profiling. Appl. Phys. Lett. 36, 295-7 (1980).CrossRefGoogle Scholar
  37. 37.
    A. Bykhovski, R. Gaska, M. S. Shur, “Piezoelectric doping and elastic strain relaxation in AlGaN-GaN heterostructure field effect transistors”, Appl. Phys. Letts. 73, .3577-9 (1998).CrossRefGoogle Scholar
  38. 38.
    F. A. Ponce, S. Srinivasan, A. Bell, L. Geng, R. Liu, M. Stevens, J. Cai, H. Omiya, H. Marui, and S. Tanaka, “Microstructure and electronic properties of InGaN alloys”, Phys. Stat. Sol. (b) 240, 273-284 (2003)CrossRefGoogle Scholar
  39. 39.
    S. Einfeldt, Z.J. Reitmeier and R.F. Davis, “Strain of GaN Layers Grown Using 6H-SiC(0001) Substrates with Different Buffer Layers”, International J. of High Speed Electronics and Systems 14, 39 (2004).CrossRefGoogle Scholar
  40. 40.
    L. Hsu, W. Walukiewicz, “Effects of piezoelectric field on defect formation, charge transfer, and electron transport at GaN/AlxGa1-xN interfaces”, Appl. Phys. Letts., .73, 339-41 (1998).CrossRefGoogle Scholar
  41. 41.
    J.A. Van Vechten, J.D. Zook, R.D. Horning, B. Goldenberg, ”Defeating compensation in wide gap semiconductors by growing in H that is removed by low temperature de-ionizing radiation”, Japanese Journal of Applied Physics, Part 1, 31, 3662 (1992).CrossRefGoogle Scholar
  42. 42.
    E. T. Yu, X. Z. Dang, L. S. Yu, D. Qiao, P. M. Asbeck, and S.S. Lau, “Schottky Barrier Engineering in III-V Nitrides via the Piezoelectric Effect”, Appl. Phys. Lett., 73(13) 1880 (1998).CrossRefGoogle Scholar
  43. 43.
    . P. Asbeck, “Polarization Barriers for GaN-Based Devices”, MRS 2001, Symposium E.Google Scholar
  44. 44.
    . Liu, Y. Zhou, J. Zhu, K. M. Lau, and K. J. Chen, “AlGaN/GaN/InGaN/GaN DH-HEMTs With an InGaN Notch for Enhanced Carrier Confinement”, IEEE Electron Device Letters 27, 10, 2006.Google Scholar
  45. 45.
    T. Palacios, A. Chakraborty, S. Heikman, S. Keller, S. P. DenBaars, and U. K. Mishra, “AlGaN/GaN High Electron Mobility Transistors With InGaN Back-Barriers”, IEEE Electron Device Letters 27, 13, 2006.CrossRefGoogle Scholar
  46. 46.
    E. Kohn, I. Daumiller, M. Kunze, M. Neuburger, M. Seyboth, T. Jenkins, J. Sewell, J. Van Norstand, Y. Smorchkova, and U.K. Mishra, “Transient Characteristics of GaN-Based Heterostructure Field-Effect Transistors”, IEEE Trans. Microwave Theory and Techniques, 51, 634,2003.CrossRefGoogle Scholar
  47. 47.
    K. Rim, J. L. Hoyt, and J. F. Gibbons, “Fabrication and Analysis of Deep Submicron StrainedSi N-MOSFET’s” IEEE Trans. on Electron Devices 47, 1406 (2000).CrossRefGoogle Scholar
  48. 48.
    P. Kirkby, P. Selway and L. Westbrook, “Photoelastic waveguides and their effect on stripegeometry GaAs/GaAlAs lasers”, J. Appl. Phys 50, 4567 (1979).CrossRefGoogle Scholar
  49. 49.
    . A. Conway, P. Asbeck and J. Moon,“The Effects of Processing Induced Stress on AlGaN/GaN HFET Characteristics,” Electronics Materials Conference, 2003.Google Scholar
  50. 50.
    . L. McCarthy, P. Kozodoy, S. DenBaars, M.Rodwell and U. Mishra, “First Demonstration of an AlGaN/GaN Heterojunction Bipolar Transistor”, Int. Symp. Comp. Semiconductors, 1998.Google Scholar
  51. 51.
    F. Ren, C. Abernathy, J. Van Hove, P. Chow, R. Hickman, J. Klaasen, R. Kopf, H. Cho, K. Jung, J. La Roche, R. Wilson, J. Han, R. Shul, A. Baca, S. Pearton, “300C GaN/AlGaN Heterojunction Bipolar Transistor”, Internet Jour. of Nitride Sem. Res. 3, 41 (1998).Google Scholar
  52. 52.
    P. M. Asbeck, E. T. Yu, S. S. Lau, W. Sun, X. Dang and C. Shi, “Enhancement of base conductivity via the piezoelectric effect in AlGaN/GaN HBTs”, Solid-State Electronics 44, 211 (2000).CrossRefGoogle Scholar
  53. 53.
    Th. Gessmann, J. W. Graff, Y.-L. Li, E. L. Waldron, and E. F. Schubert, “Ohmic contact technology in III nitrides using polarization effects of cap layers”, J. Applied Physics 92, 3740,2002.CrossRefGoogle Scholar
  54. 54.
    H. Kroemer, “Heterostructure Bipolar Transistors and Integrated Circuits”, Proc. IEEE 70, 13 (1982).CrossRefGoogle Scholar
  55. 55.
    Q. Lee, B. Agarwal, D. Mensa, R. Pullela, J. Guthrie, L. Samoska, M.J.W. Rodwell, “A >400 GHz fmax transferred-substrate heterojunction bipolar transistor IC technology. IEEE Electr. Dev.Letts., 19, 77 (1998).CrossRefGoogle Scholar
  56. 56.
    . A. Michel, D. Hanser, R.F. Davis, D. Qiao, S.S. Lau, L.S. Yu, W. Sun, P. Asbeck, “Growth and Characterization of Piezoelectrically Enhanced Acceptor-Type AlGaN/GaN Heterostructures”, 1999 Materials Research Society Fall Meeting, Boston, MAGoogle Scholar
  57. 57.
    H. M. Ng, D. Doppalapudi, T. D. Moustakas, N. G. Weimann, and L. F. Eastman. The role of dislocation scattering in n-type GaN films. Appl. Phys. Lett. 73, 821-3 (1998).CrossRefGoogle Scholar
  58. 58.
    N. G. Weimann, L. F. Eastman, D. Doppalapudi, H. M. Ng, and T. D. Moustakas. Scattering of electrons at threading dislocations in GaN. J. Appl. Phys. 83, 3656-9 (1998).CrossRefGoogle Scholar
  59. 59.
    J. W. Hsu, M. J. Manfra, D. V. Lang, K. W. Baldwin, L. N. Pfeiffer, and R. J. Molnar. Surface morphology and electronic properties of dislocations in AlGaN/GaN heterostructures. J. Electron. Mater. 30, 110-4 (2001)CrossRefGoogle Scholar
  60. 60.
    G. Koley, and M. G. Spencer. Scanning Kelvin probe microscopy characterization of dislocations in III-nitrides grown by metalorganic chemical vapor deposition. Appl. Phys. Lett. 78, 2873-5 (2001).CrossRefGoogle Scholar
  61. 61.
    B. S. Simpkins, D. M. Schaadt, E. T. Yu, and R. J. Molnar. Scanning Kelvin probe microscopy of surface electronic structure in GaN grown by hydride vapor phase epitaxy. J. Appl. Phys. 91,9924-9 (2002).CrossRefGoogle Scholar
  62. 62.
    J. W. P. Hsu, M. J. Manfra, D. V. Lang, S. Richter, S. N. G. Chu, A. M. Sergent, R. N. Kleiman, L. N. Pfeiffer, and R. J. Molnar. Inhomogeneous spatial distribution of reverse bias leakage in GaN Schottky diodes. Appl. Phys. Lett. 78, 1685-7 (2001).CrossRefGoogle Scholar
  63. 63.
    E. J. Miller, D. M. Schaadt, E. T. Yu, C. Poblenz, C. Elsass, and J. S. Speck. Reduction of reverse-bias leakage current in Schottky diodes on GaN grown by molecular-beam epitaxy using surface modification with an atomic force microscope. J. Appl. Phys. 91, 9821-6 (2002).CrossRefGoogle Scholar
  64. 64.
    E. J. Miller, D. M. Schaadt, E. T. Yu, X. L. Sun, L. J. Brillson, P. Waltereit, and J. S. Speck. Origin and microscopic mechanism for suppression of leakage currents in Schottky contacts to GaN grown by molecular-beam epitaxy. J. Appl. Phys. 94, 7611-5 (2003).CrossRefGoogle Scholar
  65. 65.
    C. C. Shi, P. M. Asbeck, and E. T. Yu. Piezoelectric polarization associated with dislocations in wurtzite GaN. Appl. Phys. Lett. 74, 573-5 (1999).CrossRefGoogle Scholar
  66. 66.
    J. P. Hirth and J. Lothe. Theory of Dislocations (McGraw-Hill, New York, 1968).Google Scholar
  67. 67.
    F. A. Ponce, D. P. Bour, W. Gotz, and P. J. Wright. Spatial distribution of the luminescence in GaN thin films. Appl. Phys. Lett. 68, 57-9 (1996).CrossRefGoogle Scholar
  68. 68.
    E. J. Tarsa, B. Heying, X. H. Wu, P. Fini, S. P. Denbaars, and J. S. Speck. Homoepitaxial growth of GaN under Ga-stable and N-stable conditions by plasma-assisted molecular-beam epitaxy. J. Appl. Phys. 82, 5472-9 (1997).CrossRefGoogle Scholar
  69. 69.
    A. F. Wright and U. Grossner. The effect of doping and growth stoichiometry on the core structure of a threading edge dislocation in GaN. Appl. Phys. Lett. 73, 2751-3 (1998).CrossRefGoogle Scholar
  70. 70.
    J. Elsner, R. Jones, M. I. Heggie, P. K. Sitch, M. Haugk, T. Frauenheim, S. Oberg, and P. R. Briddon. Deep acceptors trapped at threading-edge dislocations in GaN. Phys. Rev. B 58,12571-4 (1998).CrossRefGoogle Scholar
  71. 71.
    K. Leung, A. F. Wright, and E. B. Stechel. Charge accumulation at a threading edge dislocation in gallium nitride. Appl. Phys. Lett. 74, 2495-7 (1999).CrossRefGoogle Scholar
  72. 72.
    S. J. Rosner, E. C. Carr, M. J. Ludowise, G. G. Girolami, and H. I. Erikson. Correlation of cathodoluminescence inhomogeneity with microstructural defects in epitaxial GaN grown by metalorganic chemical-vapor deposition. Appl. Phys. Lett. 70, 420-2 (1997).CrossRefGoogle Scholar
  73. 73.
    C. Youtsey, L. T. Romano, and I. Adesida. Gallium nitride whiskers formed by selective photoenhanced wet etching of dislocations. Appl. Phys. Lett. 73, 797-9 (1998).CrossRefGoogle Scholar
  74. 74.
    P. M. Bridger, Z. Z. Bandic, E. C. Piquette, and T. C. McGill. Correlation between the surface defect distribution and minority carrier transport properties in GaN. Appl. Phys. Lett. 73, 3438-40 (1998).CrossRefGoogle Scholar
  75. 75.
    B. Heying, E. J. Tarsa, C. R. Elsass, P. Fini, S. P. Denbaars, and J. S. Speck. Dislocation mediated surface morphology of GaN. J. Appl. Phys. 85, 6470-6 (1999).CrossRefGoogle Scholar
  76. 76.
    D. M. Schaadt, E. J. Miller, E. T. Yu, and J. M. Redwing. Lateral variations in threshold voltage of an AlxGa1− xN/GaN heterostructure field-effect transistor. Appl. Phys. Lett. 78, 88-90 (2001).CrossRefGoogle Scholar
  77. 77.
    K. V. Smith, E. T. Yu, J. M. Redwing, and K. S. Boutros. Scanning capacitance microscopy of AlGaN/GaN heterostructure field-effect transistor epitaxial layer structures. Appl. Phys. Lett. 75,2250-2 (1999).CrossRefGoogle Scholar
  78. 78.
    K. V. Smith, X. Z. Dang, E. T. Yu, and J. M. Redwing. Charging effects in AlGaN/GaN heterostructures probed using scanning capacitance microscopy. J. Vac. Sci. Technol. B 18, 2304-8 (2000).CrossRefGoogle Scholar
  79. 79.
    K. V. Smith, E. T. Yu, C. Elsass, B. Heying, and J. S. Speck. Localized variations in electronic structure of AlGaN/GaN heterostructures grown by molecular-beam epitaxy. Appl. Phys. Lett. 79,2749-51 (2001).CrossRefGoogle Scholar
  80. 80.
    D. M. Schaadt, E. J. Miller, E. T. Yu, and J. M. Redwing, “Quantitative analysis of nanoscale electronic properties in an AlxGa1− xN/GaN heterostructure field-effect transistor structure,” J. Vac. Sci. Technol. B 19, 1671-4 (2001).CrossRefGoogle Scholar
  81. 81.
    D. M. Schaadt and E. T. Yu. Scanning capacitance spectroscopy of an AlGaN/GaN heterostructure field-effect transistor: analysis of probe tip effects. J. Vac. Sci. Technol. B 20, 1671-6 (2002).CrossRefGoogle Scholar
  82. 82.
    E. T. Yu, P. M. Asbeck, S. S. Lau, and G. J. Sullivan. Piezoelectric Effects in AlGaN/GaN Heterostructure Field-Effect Transistors. Electrochemical Society Proceedings 98-2, 468-78 (1998).Google Scholar
  83. 83.
    X. Zhou, E. T. Yu, D. Florescu, J. C. Ramer, D. S. Lee, and E. A. Armour. Observation of subsurface monolayer thickness fluctuations in InGaN/GaN quantum wells by scanning capacitance microscopy and spectroscopy. Appl. Phys. Lett. 85, 407-9 (2004).CrossRefGoogle Scholar
  84. 84.
    X. Zhou, E. T. Yu, D. I. Florescu, J. C. Ramer, D. S. Lee, S. M. Ting, and E. A. Armour. Observation of In concentration variations in InGaN/GaN quantum-well heterostructures by scanning capacitance microscopy. Appl. Phys. Lett. 86, 202113-1-3 (2005).Google Scholar

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© Springer Science+Business Media, LLC 2008

Authors and Affiliations

  • E. T. Yu
    • 1
  • P. M. Asbeck
    • 1
  1. 1.Electrical and Computer Engineering DeptUniversity of CaliforniaSan DiegoUSA

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