Applied Science and Convergence Technology 2011; 20(5): 361-366
Published online September 30, 2011
Copyright © The Korean Vacuum Society.
An in-situ, real-time monitoring of GaN epilayers grown by low pressure metalorganic chemical vapor deposition system modified for spectral reflectance was performed. Reflectance spectrums from 190∼861 ㎚ were observed using p-polarized light with incident angle of 75°. All reflectance spectrums showed interference oscillation caused by multiple reflection within GaN epilayers, and the spectrum from GaN with low crystalline quality showed weak reflectance intensity and much low amplitude of the oscillation because many defects in GaN resulted in light scattering and absorption. Signal variation of reflected light which was selected around strong constructive wavelength range was also observed during NH₃ supplying and NH₃ cut-off. There was no significant change in signal intensity when NH₃ cut-off for 10 sec, but it showed higher intensity when NH₃ was cut off for over 30 sec and its intensity kept unchanged. This result indicates that GaN surface was N-terminated during NH₃ supplying but Ga-terminated during NH3 cut-off because of high nitrogen equilibrium vapor pressure of GaN, and metallic Ga-terminated surface caused slightly higher reflectance intensity.
Keywords: 질화갈륨,유기금속화학기상증착법,분광 반사법,GaN,Metalorganic chemical vapor deposition,Spectral reflectance