Polarized GaN-based light-emitting diode with an embedded metallic/dielectric subwavelength grating

Highly polarized light from an InGaN/GaN light emitting diode is proposed using an embedded multi-layer metallic/dielectric sub-wavelength grating and a dielectric transition layer. Transmission of transverse magnetic mode (TTM), reflection of transverse electric mode, and polarization extinction ratio (ER) were calculated using commercial “GSOLVER” software, based on a full vector implementation of Rigorous Coupled-Wave Analysis algorithm. TTM and ER were found to be largely enhanced by the presence of the transition layer, made of MgF2 or SiO2, placed between GaN and the grating section. TTM > 95% and ER > 34 dB for closely optimized Al/MgF2 gratings were predicted. These values are significantly higher than those obtained by single-layer metallic gratings.