Gain of blue and cyan InGaN laser diodes

Experimental gain spectra of 450 and 490 nm laser diodes on c-plane GaN are analyzed by detailed comparison with the results of a fully microscopic theory. The gain calculation shows the importance of electron LO-phonon coupling. The whole spectral gain shape, not only the low energy tail, is strongly influenced by the LO-phonon contribution. The inhomogeneous broadening parameter increases by a factor of about two for the cyan laser diode in comparison with the blue laser structure. This indicates an increase in alloy and thickness fluctuations for the longer wavelength material. (C) 2011 American Institute of Physics. [doi:10.1063/1.3541785]