Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus de la UAB, 08193, Bellaterra, Catalonia, Spain.
Adv Mater. 2018 Mar;30(9). doi: 10.1002/adma.201705876. Epub 2018 Jan 12.
The design of ultrathin semiconducting materials that achieve broadband absorption is a long-sought-after goal of crucial importance for optoelectronic applications. To date, attempts to tackle this problem consisted either of the use of strong-but narrowband-or broader-but moderate-light-trapping mechanisms. Here, a strategy that achieves broadband optimal absorption in arbitrarily thin semiconductor materials for all energies above their bandgap is presented. This stems from the strong interplay between Brewster modes, sustained by judiciously nanostructured thin semiconductors on metal films, and photonic crystal modes. Broadband near-unity absorption in Ge ultrathin films is demonstrated, which extends from the visible to the Ge bandgap in the near-infrared and is robust against angle of incidence variation. The strategy follows an easy and scalable fabrication route enabled by soft nanoimprinting lithography, a technique that allows seamless integration in many optoelectronic fabrication procedures.
设计能实现宽带吸收的超薄半导体材料是光电子应用中一个长期追求的重要目标。迄今为止，解决这个问题的尝试要么依赖于使用强但窄带或更宽但中等光捕获机制。在这里，提出了一种在任意薄的半导体材料中实现宽带最佳吸收的策略，适用于所有高于带隙的能量。这源于精心设计的纳米结构薄半导体在金属膜上支撑的布儒斯特模式与光子晶体模式之间的强烈相互作用。在 Ge 超薄薄膜中展示了宽带近全吸收，其范围从可见光扩展到近红外的 Ge 带隙，并且对入射角变化具有鲁棒性。该策略遵循一种易于扩展的制造路线，该路线由软纳米压印光刻技术实现，该技术允许在许多光电子制造过程中无缝集成。
