Gain of blue and cyan InGaN laser diodes

Abstract

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

Optical Gain Spectra of a (0001) InGaN Green Laser Diode

“…Thirdly, the contribution of the electron LO-phonon interaction may broaden the gain spectra, as indicated in Ref. 15.…”

“…8,11) The luminescence inhomogeneity strongly affects the optical gain property, which is one of the most important lasing properties. To date, the optical gain properties of the (0001) LDs emitting in the near-ultraviolet (UV) to green spectral range 9,10,[12][13][14][15] and green f20 " 21g LDs 7) have been reported. Previous studies have indicated that increasing the In composition to reach a longer wavelength range causes the potential fluctuations to be more pronounced while suppressing the gain increase.…”

“…Inhomogeneous broadening of the present green LD is well suppressed compared with those in an earlier report, 10) but is similar to those of recent LDs. 15) In a separate paper, 11) inhomogeneous broadening was evaluated from the PL temperature dependence of an undoped green laser structure with the same layered structure as the LD in this study. The ''S-shape'' behavior of the PL peak as a function of temperature allows the standard deviation () of the Gaussian distribution of the DOS to be determined ( $ 20 meV).…”

Optical absorption edge broadening in thick InGaN layers: Random alloy atomic disorder and growth mode induced fluctuations

“…39 Note in this respect that the reported inhomogeneous linewidth broadening values of InGaN QWs extracted from gain spectra in state of the art cyan-green wavelength III-nitride LDs indeed exhibit a moderate increase over this wavelength range. 40,41 Finally, let us emphasize that the ability to control the surface morphology and hence the homogeneity of thick InGaN epilayers is extremely relevant in the framework of applications where the minimization of unwanted disorder is critical. This is especially the case when attempts are made to realize laser waveguides, 42 metamorphic layers, 43 or solar cells.…”

Current dependence of electro-optical parameters in green and blue (AlIn)GaN laser diodes

“…Higher threshold current and lower slope efficiency are related to lower material quality. 9 The main work for the last years has been the optimization of designs and material quality to improve laser performance. Recently, several groups have demonstrated output power up to 100 mW.…”