Interface design for electrically pumped ultraviolet nanolaser from single ZnO-nanorod

Abstract

Nanolaser, especially electrically pumped nanolaser, has attractive applications in optoelectronic or photonic interconnection, optical communication, biosensing, medical imaging and 3D display. It is in challenge how to inject charge carrier effectively for sufficient gain and how to overcome the heavy optical loss in such small sized laser device. Facing to the issues, an individual hexagonal ZnO nanorod was bonded on p-GaN to construct a heterojunction through PEDOT/HfO2 buffer in our case. Optically, the inserted buffer with low reflective index reduces the optical loss, hence decreases the lasing threshold from 1.55 μW to 1.32 μW of the nanocavity. Electrically, a reliable electrical contact is guaranteed by inserting the organic polymer PEDOT facilely. More importantly, PEDOT and HfO2 form a step energy band configuration in the p-GaN/ZnO heterojunction for efficient charge carrier injection, thus contribute to improve radiative recombination. As the injection current reached 6 mA, the FWHM of the emission spectrum quickly narrowed from ~ 30 to 1.4 nm, and the intensity increase dramatically. This demonstrated the UV lasing behaviors in a nano-scaled heterojunction diode.