Effect of injection current on the optical polarization of AlGaN-based ultraviolet light-emitting diodes.

The injection current dependence of optical polarization of ultraviolet (UV) light-emitting diodes (LEDs) emitting at wavelength of 310 nm and 277 nm was investigated by electroluminescence (EL) measurements. For both diodes, it was found that the degree of polarization (DOP) decreased obviously as the injection current increased. We attribute the decrease in DOP to the different changing trend of the intensity of the light emission from transverse electric (TE) polarization (E⊥c) and transverse magnetic (TM) polarization (E∥c) as the injected carriers occupy higher states above k = 0 with increasing the injection current. For the 277 nm LED, even the polarization switching from TE to TM mode was observed.