SPATIAL DISTRIBUTIONS OF NEAR-BAND-GAP UV AND YELLOW EMISSION ON MOCVD GROWN GAN EPIFILMS

Near-band-gap UV and yellow band emission from metal-organic chemical vapor deposition grown GaN films on sapphires are investigated under l aser excitation. The intensities of the UV and the yellow peaks increa se at different rates as the entrance slit width of the spectrometer i ncreases. The spatial distribution of the luminescence emission is ana lyzed through the dependence of photoluminescence intensity on the sli t widths of the spectrometer. The yellow emission originates from a sp ot with a size about 1.5 times larger in diameter than the UV emission . Using an absorption mechanism, a Lorentzian line-shape distribution ft with the data gives estimated effective absorption coefficients of 47 cm(-1) for the UV signal at 364 nm and of 32 cm(-1) for the yellow signal at 546 nm, which agrees perfectly with the ones from an exponen tial decay fit. Dependence of UV-to-yellow peak ratio on the slit widt hs of the spectrometer, and consistence with possible origins of yello w luminescence is discussed. [SO163-1829(98)03132-4].