Surface mapping of carrier density in a GaN wafer using a frequency-agile THz source

S. Ohno; A. Hamano; K. Miyamoto; C. Suzuki; H. Ito

doi:10.2971/jeos.2009.09012

Journal of the European Optical Society - Rapid publications, Vol 4 (2009)

Surface mapping of carrier density in a GaN wafer using a frequency-agile THz source

S. Ohno, A. Hamano, K. Miyamoto, C. Suzuki, H. Ito

Abstract

We developed a method for mapping the carrier density on a semiconductor substrate surface based on terahertz (THz)-reflective measurement. Reflectivity in the THz-frequency region away from the optical phonon frequency is sensitive to the carrier density in semiconductors. However, reflectivity in the optical phonon frequency regions is around 1.0, independent of the carrier density. We developed a THz-reflective spectral imaging system using a frequency-agile, ultra-widely tunable THz source (1 - 40 \THz). Different reflective images were obtained from GaN samples of carrier density 2.5x10^{16}cm^{-3}, 1.0x10^{18}cm^{-3}, and 1.5x10^{18}cm^{-3} using 22.7 and 26.5 THz. The image contrast reflected the GaN crystals' carrier density.

Full Text: PDF

Citation Details

Cite this article

References

N. Harrick, "Semiconductor surface properties deduced from free carrier absorption and reflection of infrared radiation" J. Phys. Chem. Solids 14, 60 (1960).

J. Majewski and D. Matthiesen, "Quantative infrared imaging for measurement of dopant distribution in gallium arsenide" J. Cryst. Growth 137, 249 (1994).

C. Drake, S. Deshpande, and S. Seal, "Determination of free carrier density and space charge layer variation in nanocrystalline In3+ doped tin oxides using Fourier transform infrared spectroscopy" Appl. Phys. Lett. 89, 143116 (2006).

A. J. Huber, F. Keilmann, J. Wittborn, J. Aizpurua, and R. Hillenbrand, "Terahertz Near-Field Nanoscopy of Mobile Carriers in Single Semiconductor Nanodevices" Nano Lett. 8, 3766-3770 (2008).

H. Ito, K. Suizu, T. Yamashita, A. Nawahara, and T. Sato, "Random Frequency Accessible Broad Tunable Terahertz-Wave Source Using Phase-Matched 4-Dimethylamino-N-methyl-4-stilbazolium Tosylate Crystal" Jpn. J. Appl. Phys. 46, 7321 (2007).

V. Bougrov, M. E. Levinshtein, S. L. Rumyantsev, and A. Zubrilov, Properties of Advanced Semiconductor Materials GaN, AlN, InN, BN, SiC, SiGe (John Wiley & Sons, Inc., New York, 2001).

R. Holm, J. Gibson, and E. Palik, "Infrared reflectance studies of bulk and epitaxial-film n-type GaAs" J. Appl. Phys. 48, 212 (1977).

A. Barker and M. Ilegems, "Infrared Lattice Vibrations and Free- Electron Dispersion in GaN" Phys. Rev. B 7, 743 (1973).

Y. Fu, M. Willander, Z.-F. Li, and W. Lu, "Electron mobilities, Hall factors, and scattering processes of n-type GaN epilayers studied by infrared reflection and Hall measurements" Phys. Rev. B 67, 113313 (2003).