Exploring superlattice DBR effect on a micro-LED as an electron blocking layer.

The role of a superlattice distributed Bragg reflector (SL DBR) as the p-type electron blocking layer (EBL) in a GaN micro-light-emitting diode (micro-LED) is numerically investigated to improve wall-plug efficiency (WPE). The DBR consists of AlGaN/GaN superlattice (high refractive index layer) and GaN (low refractive index layer). It is observed that the reflectivity of the p-region and light extraction efficiency (LEE) increase with the number of DBR pairs. The AlGaN/GaN superlattice EBL is well known to reduce the polarization effect and to promote hole injection. Thus, the superlattice DBR structure shows a balanced carrier injection and results in a higher internal quantum efficiency (IQE). In addition, due to the high refractive-index layer replaced by the superlattice, the conductive DBR results in a lower operation voltage. As a result, WPE is improved by 22.9% compared to the identical device with the incorporation of a conventional p-type EBL.