In this paper, we report the electrical and optical characteristics of Si delta-doped AlGaN cladding layers, p-cladding structure optimization and the impact on the efficiency of 340nm AlGaN UV LEDs. Compared to the uniformly doped n-AlGaN layer, adding Si δ-doping layers reduced the sheet resistance by improving both the Hall mobility and carrier concentration. Increasing the number of Si δ-doped layers further lowered the sheet resistance without cracking the material. The δ-doped layers in n-Al0.3Ga0.7N improved the optical properties by enhancing near band edge emission as much as 2-fold relative to deep level emission. Additionally, δ-doping in n-AlGaN layers had no detrimental effect on the optical transparency of the LEDs. The p-cladding layer was found to have a strong absorption at 340nm. Reducing the p-GaN cap layer from 35nm to 10nm tripled the light emission intensity. By optimizing the n- and p-AlGaN cladding layers, a highly efficient UV LED at 340nm was achieved with 1mW output under 800mA/mm2 DC drive current.
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Xin, H.P., Flynn, J.S., Dion, J.A. et al. Electrical and Optical Characteristics of Delta Doped AlGaN Cladding Layer Materials for Highly Efficient 340nm Ultra Violet LEDs. MRS Online Proceedings Library 798, 366–371 (2003). https://doi.org/10.1557/PROC-798-Y3.10