The ablative decomposition of GaN films induced with a XeCl excimer laser ((lambda) equals 308 nm) was investigated for a potentially low-damage surface planarization process. Samples, 2-micrometers -thick, were grown on (0001) sapphire by ammonia molecular beam epitaxy. They had a characteristic micro-hillock type surface morphology with a roughness, averaged over 5 x 5 micrometers ² area, typically, of 13 nm. Following the laser irradiation, this roughness could be reduced to 3.6 nm. The results indicate that the ablation process follows the Lambert-Beer's law, with an absorption coefficient of 3 x 10⁵ cm^-1. The experiment was carried out with relatively short pulses ((tau) equals 10 ns), which appear to be responsible for the observed onset of the laser-induced decomposition of GaN and surface planarization at significantly smaller laser fluences than reported in the literature. The ability to carry out decomposition of GaN with low laser fluences is of practical importance for achieving a low-damage GaN planarization process and/or intentional delaminating of this material from the sapphire substrate by the back side irradiation technique.

Date Published: 29 June 2001
PDF: 6 pages
Proc. SPIE 4274, Laser Applications in Microelectronic and Optoelectronic Manufacturing VI, (29 June 2001); doi: 10.1117/12.432536

Published in SPIE Proceedings Vol. 4274:
Laser Applications in Microelectronic and Optoelectronic Manufacturing VI
Malcolm C. Gower; Henry Helvajian; Koji Sugioka; Jan J. Dubowski, Editor(s)