Time-resolved photoluminescence study of GaN grown by metalorganic chemical vapor deposition

We have investigated the time decay of the photoluminescence (PL) at room t emperature of high-quality (HQ) and low-quality (LQ) GaN epitaxial layers g rown on sapphire by metalorganic chemical vapor deposition. For undoped and Si-doped HQ GaN, the full-width at half-maximum of the (1 0 2) X-ray diffr action curve is 562 and 427 arcsec and the dislocation density is 4 x 10(8) and 2 x 10(8) cm (- 2), respectively. It is found that the PL of HQ GaN ha s a higher intensity and decays slower than that of LQ GaN. The PL decay ti me is found to be much longer in HQ GaN. The dual-exponential decay times a re 50 and 250 ps for undoped HQ GaN, and 150 and 740 ps for Si-doped HQ GaN . To our knowledge, the decay times of 150 and 740 ps are the longest ever reported in GaN thin films at room temperature. Furthermore, the characteri stics of PL decay with different excitation intensities and laser beam focu sing conditions are also reported. (C) 2000 Elsevier Science B.V. All right s reserved.