Numerical Modeling for 250 nm DUV LEDs With Discrete p-type Functional Layers to Manage Both Carrier and Photon Transport

Abstract

Deep-ultraviolet light-emitting diodes (DUV LEDs) are encountering low external quantum efficiency (EQE) and light output power (LOP) due to the strong optical absorption to DUV light and the poor carrier injection efficiency. To solve these issues, we design and optimize a 250 nm DUV LED structure with thin quantum wells and discrete p-type functional layers. The discrete p-type functional layers consist of a high Al composition-gradient layer (layer I) and a low Al composition-gradient layer (layer II). Calculated results indicate that the use of thin quantum wells can rearrange the valence subband distributions to increase the transverse-electric (TE) polarized emission, thereby enhancing light extraction efficiency (LEE). Additionally, the LEE can also be increased by optimizing the thickness of the discrete p-type functional layers, i.e., modulating the optical absorption effect and the optical cavity effect. Meanwhile, we also investigate the impact of different negative polarization bulk charge densities on the electron and hole injections by changing the thickness of layer I and layer II, which can obtain the optimized internal quantum efficiency (IQE) for the 250 nm DUV LED. Therefore, when compared with conventional DUV LEDs, the proposed LED architectures improve the EQE and optical power if the discrete p-type functional layers are properly designed.