Ve. Kudryashov et al., Influence of a sapphire substrate on the emission spectra of gallium nitride light-emitting diodes, TECH PHYS L, 25(7), 1999, pp. 536-537
The emission spectra of green light-emitting diodes based on InGaN/AlGaN/Ga
N heterostructures revealed a weak thin doublet line at the long-wavelength
edge. This line is ascribed to luminescence of residual Cr3+ impurity ions
in the sapphire substrate (similar to ruby, Al2O3:Cr, doublet wavelengths
692.9 and 694.3 nm). The ions are excited by visible diode radiation which
is close to the absorption bands of the Cr3+ ions. It is shown that ruby lu
minescence may be excited by radiation from blue and green GaN light-emitti
ng diodes. (C) 1999 American Institute of Physics. [S1063-7850(99)01307-5].