SUBSTRATE NITRIDATION EFFECT AND LOW-TEMPERATURE GROWTH OF GAN ON SAPPHIRE (0 0 0 1) BY PLASMA-EXCITED ORGANOMETALLIC VAPOR-PHASE EPITAXY

Nitridation of sapphire (0001) substrate by plasma-excited N-2 for org anometallic vapor-phase epitaxy (OMVPE) of GaN is investigated. The su rface structure of nitrided layer and the relationship between the nit ridation conditions and the crystalline quality of GaN epitaxial lag e r are investigated The substrate surface becomes amorphous by the nitr idation. An optimized nitridation improves the crystalline quality of the GaN epitaxial layer and is effective to decrease the growth temper ature. A clear and transparent GaN epitaxial layer with a mirror-like surface can be grown at temperature as low as 550 degrees C. Room temp erature photoluminescence indicates no deep level emission but only a strong band-edge emission from the GaN layers grown at 680 degrees C.