Optical Characterization of High Quality GaN Produced by High Rate Magnetron Sputter Epitaxy
- PDF / 169,565 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 27 Downloads / 164 Views
L4.12.1
Optical Characterization of High Quality GaN Produced by High Rate Magnetron Sputter Epitaxy Minseo Park, E. Carlson3 Y. C. Chang1, J. F. Muth1, J. Bumgarner3, R. M. Kolbas1, J. J. Cuomo, R. J. Nemanich2 Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27695 1 Department of Electrical and Computer Engineering, North Carolina State University, Raleigh, NC 27695 2 Department of Physics, North Carolina State University, Raleigh, NC 27695 3 Kyma Technologies, Inc., 8829 Midway West Road, Raleigh, NC 27617 ABSTRACT The thick films of GaN were investigated using X-ray diffraction, micro-Raman spectroscopy and photoluminescence spectroscopy. The thick films of GaN were prepared on (0001) sapphire using high rate magnetron sputter epitaxy with growth rates as high as 10-60 µm/min. The width of the X-ray rocking curve ((0002) reflection) for the sample produced by this method is ~300 arc-sec. Only the allowed modes were observed in the polarized Raman spectra. The background electron concentration is lower than 3×1016 cm-3, which was determined from the Raman spectra. The phonon lifetime determined from Raman E2(2) mode was 1.6 ps, which is comparable to that of bulk single crystal GaN grown by sublimation (1.4 ps). The full-width-at-half-maximum of the near band-edge photoluminescence peak obtained at 77K is ~100 meV. INTRODUCTION Wide band gap III-V nitrides semiconductors such as gallium nitride (GaN) are important materials for optoelectronic applications in the short-wavelength spectral region. GaN can be prepared using a variety of techniques such as organometallic vapor phase epitaxy (OMVPE) and molecular beam epitaxy (MBE). It can also be produced using sputtering, but the sputtering process has not been considered as a method to produce high quality epitaxial films of GaN. After the sputtered GaN was synthesized by Hovel and Cuomo [1], only a few worker have reported on sputter epitaxy of GaN [27].2,3,4,5,6]. Recently, we have demonstrated that high quality GaN films can be grown using sputtering, and the full-width-at-half-maximum of X-ray rocking-curve for this sample is ~300 arc-sec. The smallest value reported until now was 620 arc-sec, which was produced by Webb et al. using magnetron sputter epitaxy [7]. Values for the FWHM of (0002) rocking curves for thin GaN films grown via HVPE directly on sapphire have been previously reported in the range of 200 to 600 arc-sec [8, 9, 10]. Note that FWHM for GaN grown by OMVPE can be as low as ~30 arc-sec [11]. In the present investigation, we have used X-ray diffraction, micro-Raman scattering, and photoluminescence spectroscopy to assess the crystal quality of the sputtered GaN.
L4.12.2
EXPERIMENTAL Thick films of GaN were prepared on sapphire substrates using high-rate DC reactive magnetron sputter epitaxy. As a target, pure gallium (99.9999%) was contained in a large area stainless steel cup (6 in.). This sputtering technique allows the growth of high quality GaN layers on large area substrates (up to 4 in.) wit
Data Loading...
