Shutterless nitrogen flux modulation using a dual-mode rf-plasma operation during RF-MBE growth of GaN

A convenient and efficient version of the nitrogen flux modulation technique is demonstrated, in which the reactive nitrogen flux can be completely switched on and off, utilizing the bistability between the so-called bright- and dark-mode plasmas instead of using a shutter plate. The reactive nitrogen flux found to be controlled practically as clearly shown by a plasma spectral investigation and the linear variation in the growth rate of GaN with respect to a nitrogen-supply duration. N-polarity GaN films were grown using a nitrogen flux modulation as well as a migration enhanced epitaxial growth sequences with different durations of the reactive nitrogen supply. Their structural properties, especially the surface morphology and the density of the screw-component of threading dislocations estimated from the X-ray diffraction line width, found to be very sensitive to the nitrogen supply duration as well as the growth sequences.