Terahertz emission spectroscopy on Eu-doped GaN superlattice LEDs

Eu-doped gallium nitride (GaN) is a promising candidate for GaN-based red light-emitting diodes (LEDs). By utilizing a multilayer structure (MLS) of alternating undoped and Eu-doped GaN as the active layer, the device performance of Eu-doped GaN LEDs was significantly enhanced. However, the mechanism of this improvement has not yet been understood. To better understand the enhanced device performance, we evaluated the carrier dynamics in the structures using terahertz (THz) emission spectroscopy. Our results suggest that the carrier mobility in the MLS is lower than in bulk Eu-doped GaN. Furthermore, the excitation photon energy dependence of the THz emission revealed that the Eu-doped layer had a smaller bandgap than the undoped GaN layer, resulting in the potential barriers within the MLS samples. We attributed the improvement in LED performance to improved electron capturing within the active regions in MLS.