Modulating the Layer Resistivity by Band-Engineering to Improve the Current Spreading for DUV LEDs

In this letter, we propose to enhance the hole injection efficiency by modulating the layer resistivity in the n-AlGaN layer for 280 nm AlGaN based deep ultraviolet light-emitting diodes (DUV LEDs). The layer resistivity for the n-AlGaN layer is controlled by generating the energy barriers, which is enabled by locally engineering the energy band gap for the n-AlGaN layer, such that a thin n-AlGaN layer with high Al composition is inserted before growing the subsequent multiple quantum wells (MQWs). As a result, such inserted n-AlGaN layer is able to tune the current flow path, i.e., improving the current spreading effect in the p-type hole injection layer. The improved current spreading effect favors the promoted hole injection into the active region. We numerically and experimentally obtain the improved external quantum efficiency, the optical power, and the wall-plug efficiency, thanks to the better current spreading and the correspondingly enhanced hole injection capability.