Dislocation reduction in GaN grown by hydride vapor phase epitaxy via growth interruption modulation

Thick GaN layers have been deposited on c-Al2O3 (0001) substrates using hyd ride vapor phase epitaxy by modulating the growth process via switching on/ off GaN growth. Cathodoluminescence and transmission electron microscopy im ages of the cross-sectional structure show that there are separated multila yers structure in the GaN films. The dislocations density decreases from 10 (10) cm(-2) in the initial layer to 10(9)-10(8) cm(-2) in the subsequently grown layer and then to 10(7) cm(-2) in the top layer. This shows that the interruption of the growth process is helpful for suppression of structural defects. X-ray diffraction and photoluminescence measurements also demonst rate the high quality of the GaN films. (C) 2001 American Institute of Phys ics.