We demonstrate what is to our knowledge the first example of four-photon luminescence microscopy in GaN and apply it to quality mapping of bulk GaN. The simultaneously acquired second- and third-harmonic generation can be used to map the distribution of the piezoelectric field and the band-tail state density, respectively. Through spectrum- and power-dependent studies, the fourth power dependence of the band edge luminescence is confirmed. The superb spatial resolution of the four-photon luminescence modality is also demonstrated. This technique provides a high-resolution, noninvasive monitoring and tool for examining the physical properties of semiconductors.
© 2005 Optical Society of America
Shi-Wei Chu, Ming-Che Chan, Shih-Peng Tai, Stacia Keller, Steven P. DenBaars, and Chi-Kuang Sun, "Simultaneous four-photon luminescence, third-harmonic generation, and second-harmonic generation microscopy of GaN," Opt. Lett. 30, 2463-2465 (2005)