Polarization-resolved electroluminescence study of InGaN/GaN dot-in-a-wire light-emitting diodes grown by molecular beam epitaxy

The polarization properties of light emission from InGaN nanowire (NW) light-emitting diodes (LEDs) have been studied with the use of goniometric setup. A maximum polarization ratio of ∼0.7 has been obtained from the edge emission of NW array-based LEDs and the light is mainly polarized parallel to the c-axis of NWs. The nearly isotropic polarization response from a core-shell NW LED structure is also observed, and it is found that the degree of polarization is strongly depended on the NW diameter. With the growth of the AlGaN shell, the resulting diameter of core-shell NWs becomes larger and is comparable to the emission wavelength, thus weakening the optical confinement effect and the polarization behavior. The size-dependent polarization properties of NW structures are further verified by the finite-difference time-domain simulation. NWs with diameters much less than the emission wavelength render a strong contrast between the p- and s-polarized light emissions. (Left) FE-SEM image of MBE-grown NWs covered with polyimide. (Right) Plot of integrated electroluminescence intensity as a function of polarizer angle for a NW LED.