Significant improvement of injection efficiency in deep-UV LD structures by light Mg doping in p-core layer

Abstract

Improvement of carrier injection efficiency is essential to achieve lower threshold and shorter wavelength in deep-ultraviolet laser diodes. We have confirmed that the introduction of electron blocking layer and Mg doping layer into the core layer significantly improves the injection efficiency. In this study, we show that optimizing the Mg doping level in the core layer improves the external quantum efficiency by a factor of about 10 compared to the non-doped sample. The dependence of the external quantum efficiency on Mg flow rate can be interpreted in terms of a reduction of the dip at the p-side core/cladding interface in the conduction band. The dip is expected to be suppressed by ionized Mg activated by the Poole-Frenkel effect, resulting in improved carrier injection efficiency. A remarkable improvement in efficiency is also observed when the Mg doping region is limited to the vicinity of the core/cladding layer interface.