IR Laser Induced Emission Spectra of GaN Nanoceramic

Abstract

Currently, the researchers from around the world pay a lot of attention to search new white light generation sources. Such a device would have huge application potential in the lighting industry. The advantage of a broadband white light source is no necessity to mix few emission lines to obtain a white luminescence, as it is in case of the LED devices. Here, we investigate the broadband laser induced emission spectra of GaN nanoceramic measured under three different infrared excitation lines (1064, 975 and 808 nm). The GaN powder was obtained by thermal decomposition method while the nanoceramic was prepared using low temperature high pressure (LTHP) technique. The sample crystallizes in the hexagonal wurtzite structure and theoretical value of their average grain size calculated using Scherrer equation was 12 nm. The optical characterization of LIE spectra of GaN nanoceramic included the measurements of emission intensity as a function of power density, ambient pressure and luminescence kinetics. The emission spectra were recorded in both VIS (400-900 nm) and NIR (1200-2500 nm) regions (Fig. 1a,1b). It was found that the power dependence exhibit threshold behavior typical for avalanche process for all three excitation lines. The luminescence kinetics measurements show that rise and decay times of LIWE are extremely short in comparison to dielectric materials. It turned out that calculated x and y parameters of recorded emissions lie in the warm region of the CIE chromaticity diagram confirming their low color temperature regardless of the excitation wavelength (Fig. 1c). Finally, a general mechanism of LIE spectra in GaN nanoceramic is discussed.Figure 1. The LIWE intensity of GaN nanoceramic under 975 nm as a function of increasing pumping power density in VIS and NIR regions (a,b). The CIE chromaticity diagram of LIWE generated from GaN nanoceramic upon three various excitation wavelengths (c). The image of LIWE during experiment (d). Figure 1