Promising features of In$_{0.5}$Ga$_{0.5}$N/Al$_{0.2}$Ga$_{0.8}$N quantum dot lasers


Abstract: The group-III nitrides, InN, GaN, and AlN, and their alloys have emerged as one of the most important material classes for optoelectronic devices. The incorporation of quantum dots (QDs) as active material improves the performance of conventional optoelectronic devices, such as laser diodes. In this study, we present a theoretical analysis of the gain characteristics of In$_{x}$Ga$_{1-x}$N/Al$_{0.2}$Ga$_{0.8}$N three-dimensional quantum box lasers, based on the density matrix theory of semiconductor lasers with relaxation broadening. The study is done on three samples of QDs: GaN/Al$_{0.2}$Ga$_{0.8}$N, In$_{0.3}$Ga$_{0.7}$N/Al$_{0.2}$Ga$_{0.8}$N, and In$_{0.5}$Ga$_{0.5}$N/Al$_{0.2}$Ga$_{0.8}$N. A comparative study of the gain spectra of GaN/Al$_{0.2}$Ga$_{0.8}$N-based quantum-well and QD lasers is also presented for various side lengths. The variation of peak gain on carrier density is presented as well. The effect of indium composition on the variation in modal gain versus current density and the threshold current with inverse cavity length is plotted. The results show that the In$_{0.5}$Ga$_{0.5}$N/Al$_{0.2}$Ga$_{0.8}$N QD laser emitting at red wavelength has a higher value of optical gain of 19,575 cm$^{-1}$ and a lower threshold current density of 143.9 A/cm$^{2}$.

Keywords: Quantum dot, quantum-well lasers, optical gain, nitride semiconductors

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