Ahmad Fajri Faris Azim, Mukherjee Anjan, Naskar Suraj, Ahmad Noorden Ahmad Fakhrurrazi, Abass Aimi
ams OSRAM Group, Leibnizstraße 2, Regensburg, Germany.
Centre for Advanced Optoelectronics Research, Kulliyyah of Science, International Islamic University Malaysia, Kuantan, Pahang, Malaysia.
Sci Rep. 2024 Jun 19;14(1):14108. doi: 10.1038/s41598-024-64689-y.
Deep ultraviolet light-emitting diodes (DUV LEDs) typically suffer from strong parasitic absorption in the p-epitaxial layer and rear metal contact/mirror. This problem is exacerbated by a substantial portion of the multiple quantum well (MQW) emissions having a strong out-of-plane dipole component, contributing to emission in widely oblique directions outside the exit cone of the front semiconductor emitting surface. To address this, we propose an architecture that leverages such a heavily oblique angular emission profile by utilizing spaced-apart or scattered volume emitter micropixels that are embedded in a low-index dielectric buffer film with a patterned top surface. This approach achieves high light extraction efficiency at the expense of enlarging the effective emission area, however, it does not require a high-index (e.g., sapphire) substrate or a lens or a nanotextured epi for outcoupling purposes. Hybrid wave and ray optical simulations demonstrated a remarkable larger than three to sixfold increase in light extraction efficiency as compared to that of a conventional planar LED design with a sapphire substrate depending on the assumed epi layer absorption, pixel size, and ratio of light emission area to the MQW active area. An extraction efficiency three times greater than that of a recent nanotextured DUV LED design was also demonstrated. This architecture paves the way for DUV LEDs to have a plug efficiency comparable to that of mercury lamps while being significantly smaller.
深紫外发光二极管（DUV LED）通常在p外延层和背面金属接触/反射镜中存在强烈的寄生吸收。多量子阱（MQW）发射的很大一部分具有很强的面外偶极子分量，这使得发射方向广泛倾斜于前半导体发射表面的出射锥之外，从而加剧了这个问题。为了解决这个问题，我们提出了一种架构，通过利用嵌入具有图案化顶面的低折射率介电缓冲膜中的间隔开或分散的体发射微像素，来利用这种严重倾斜的角发射分布。这种方法以扩大有效发射面积为代价实现了高光提取效率，然而，它不需要用于光外耦合目的的高折射率（例如蓝宝石）衬底、透镜或纳米纹理外延层。混合波动和射线光学模拟表明，与具有蓝宝石衬底的传统平面LED设计相比，根据假设的外延层吸收、像素尺寸以及发光面积与MQW有源区的比例，光提取效率显著提高了三到六倍以上。还展示了一种比最近的纳米纹理DUV LED设计高三倍的提取效率。这种架构为DUV LED实现与汞灯相当的插入效率同时显著更小铺平了道路。
