High-Efficiency and Stable Emission Wavelength Red InGaN Light-Emitting Diodes with Porous Distributed Bragg Reflectors on Si Substrates

Red InGaN light-emitting diodes (LEDs) with porous GaN distributed Bragg reflectors (DBRs) were demonstrated with high directional emission properties, stable emission wavelengths, and prevention of light absorption by the Si substrate. The amounts of peak wavelength that blue-shifted were measured at the values of 18.2 nm for the nontreated red LED and 2.4 nm for the treated red LED with embedded porous GaN DBR structures from a 0.2 to 5.0 mA injection current. The small peak wavelength blue shift, stable emission wavelength, and narrow line width values were shown in the treated red LED due to partially releasing the compressive strain in InGaN active layers by inserting a porous GaN DBR structure. The electroluminescence light emission intensities of the red LED with DBR structures were higher than those of the red LED structures without treatment due to the light reflected by the porous GaN DBR structure and the prevention of light absorption by the Si substrate. From electroluminescence far-field patterns, the divergent angles were reduced from 120 to 85° for the red LED without and with embedded porous GaN DBR structure, respectively. The red LED structures with the embedded porous GaN DBRs consisted of stable emission wavelength, small divergent angles, and narrow line width properties, which have the potential of being used for directional light-emitting sources in micro-LED displays and vertical-cavity surface-emitting laser applications.