ON THE KINETICS OF GROWTH OF HIGHLY DEFECTIVE GAN EPILAYERS AND THE ORIGIN OF THE DEEP TRAP RESPONSIBLE FOR YELLOW-BAND LUMINESCENCE

The kinetics of growth of GaN/(0001) sapphire heteroepitaxial films ha ve been examined in the relatively low substrate temperature range, 56 0-640 degrees C, using the reflection high energy electron diffraction (RHEED) specular reflection intensity monitoring technique. In partic ular, an alternate element exposure method of growth was employed in w hich Ga and N atoms were supplied separately (rather than simultaneous ly, as in conventional molecular beam epitaxy) to the substrate with t he inclusion of a time delay between successive Ga flux and N flux exp osures. We interpret the observed time dependent recovery of the RHEED specular reflection intensity during the time delay phases to be asso ciated with Ga-N surface molecule migration on Ga-terminated surfaces and the activation energy for this migration process was determined to be 1.45+/-0.25 eV. (C) 1997 American Institute of Physics.