Effect of GaNP Buffer Layer on AlGaN Epilayers Deposited on (0001) Sapphire Substrates by Metalorganic Chemical Vapor Deposition

Abstract

Al x Ga 1Àx N (x 0:1) epilayers grown on (0001) sapphire substrates by low-pressure metalorganic chemical vapor deposition with low-temperature (LT)-GaNP buffer have been characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). It is found that the full width at half maximum (FWHM) values of the GaNP-buffer-based Al x Ga 1Àx N (x 0:1) epilayers decrease are lower than that of the conventional GaN-buffer-based Al x Ga 1Àx N (x 0:1) epilayers, but the difference becomes smaller as the Al composition increases. These results could be mainly attributed to a longer diffusion length with the GaNP buffer layer than with the GaN buffer layer.

Effect of middle temperature intermediate layer on crystal quality of AlGaN grown on sapphire substrates by metalorganic chemical vapor deposition

“…The dislocations formed the curved and made dislocation loop around MTIL. The growth of AlGaN with in over 10% Al composition, the selectively grown region in the initial growth stage almost disappears and the vertical direction growth mode is predominant [3]. Therefore, the dislocations went up straight toward the dislocations went up straight toward the AlGaN surface and became high dislocation density.…”

“…By using the GaNP buffer technique, the size and the density of the nucleation islands were optimally controlled and the lateral growth areas were increased. Applying this technique to AlGaN film growth, we also found that the crystal quality in the range of less than 10% of aluminum composition was improved [3]. However, for over 10% Al composition, the film with device quality could not be obtained and the film had high dislocation density.…”