Reduction in the series resistance of the distributed Bragg reflector in vertical cavities by using quasi-graded superlattices at the heterointerfaces

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Abstract
Surface emitting optical devices with a vertical cavity have been investigated for applications in optical interconnections. To integrate these devices into a two-dimensional array, it is necessary to improve the conversion efficiency from electrical power to optical power. To meet this requirement, the series resistance of the distributed Bragg reflectors that form the vertical cavity must be reduced. This article demonstrates the reduction in the series resistance of the distributed Bragg reflector by introducing quasi-graded superlattices at the heterointerfaces. By using this structure, we obtain a low series resistance distributed Bragg reflector without compromising the high reflectivity. The mechanism of the reduction in the series resistance is studied and it is found that an increase in tunneling current leads to a decrease in the resistance. The dependence of tunneling current on doping concentration of the distributed Bragg reflector and the superlattice structure is also discussed.