GaN thin films produced by pulsed laser deposition

Well-oriented GaN films were grown on (112¯0) sapphire substrates in ultra-high vacuum by pulsed laser deposition. Film quality is comparable to that of those grown by conventional epitaxial techniques. Films deposited at a laser fluence of 2.0 J cm−2 and 700°C showed a pure wurtzite phase. Scanning electron microscopy indicated that at 700°C and 2.0 J cm−2 smooth, continuous and droplet-free GaN films were obtained. The band-gap, obtained from transmission measurements was 3.3 eV. Violet and yellow photoluminescence was found in all samples but 60 nm films showed a strong violet emission peak centered at 3.2 eV with a full width at half maximum of 0.2 eV whereas the dominant feature of 180 nm films was a broad peak in the yellow centred at 2.1 eV.