Scanning near-field optical microscopy (SNOM) analysis of MOVPE InN

Hiroshi Miwa ,  Yasuhiko Nagai ,  Akihiro Hashimoto ,  Akio Yamamoto 

University of Fukui (U. Fukui), 3-9-1 Bunkyo, Fukui 910-8507, Japan

Abstract

Recently, we have attained a mobility of 1100 cm2/Vs and carrier concentration of 4.5×1018cm-3 for InN films grown by the atmosphere pressure MOVPE [1]. However, compared with MBE InN, MOVPE InN still has inferior electrical and optical properties. FWHM for PL peaks for MOVPE InN [2] is considerably larger than that for MBE InN [3], in spite of the similar PL peak energies. Therefore, MOVPE InN seems to have a large nonuniformity in their properties. In this paper, we report the scanning near-field optical microscopy (SNOM) analysis of MOVPE InN to get information about the nonuniformity. Samples of InN are grown at 600ºC on nitrided (0001) sapphire substrates without or with a GaN buffer by the atmospheric-pressure MOVPE. In the SNOM system (Type NFS-220FK, JASCO Corp., Japan.), a green laser (l= 532 nm) is used as an excitation source. A probe with an aperture size of 100-500 nmφ is used to illuminate the sample surface and collect near-field light (illumination-collection mode). A near-field PL spectrum and its intensity mapping are successfully obtained for InN films at room temperature for the first time. By monitoring a probe movement at each point of measurement, surface topography is also obtained. A large nonuniformity in the near-field PL mapping is observed for samples grown without buffer. Compared with films grown without buffer, those grown with a GaN buffer have a excellent uniformity in near-field PL intensity. Thus, the use of the buffer is found to improve effectively the in-plane uniformity of the near-field PL intensity. This seems to be due to the uniform nucleation of InN on the buffer. [1] A. Yamamoto et al., (will be presented in ICNS-6). [2] A. Yamamoto et al., J. Cryst. Growth 261 (2004) 275. [3] F. Chen et al., Physica E 20 (2004) 308.

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Presentation: poster at E-MRS Fall Meeting 2005, Symposium A, by Hiroshi Miwa
See On-line Journal of E-MRS Fall Meeting 2005

Submitted: 2005-05-20 12:55
Revised:   2009-06-07 00:44
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