Electrical and Optical Characteristics of Delta Doped AlGaN Cladding Layer Materials for Highly Efficient 340nm Ultra Violet LEDs

摘要

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-Al_(0.3)Ga_(0.7)N 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/mm~2 DC drive current.