Enhancing absorption in optically thin semiconductors is the key in the development of high-performance optical and optoelectronic devices. In this paper, we resort to the concept of degenerate critical coupling and design an ultra-thin semiconductor absorber composed of free-standing GaAs nanocylinder arrays in the near infrared. The numerical results show that perfect absorption can be achieved through overlapping two Mie modes with opposite symmetry, with each mode contributing a theoretical maximum of 50% in their respective critical coupling state. The absorption also shows the polarization-independent and angle-insensitive robustness. This work, together with the design concept, opens up great opportunities for the realization of high-efficiency semiconductor devices, including optical emitters, modulators, detectors, and sensors.

增强光学薄半导体中的吸收是开发高性能光学和光电器件的关键。在本文中，我们采用简并临界耦合的概念，设计了一种由近红外独立式 GaAs 纳米圆柱阵列组成的超薄半导体吸收器。数值结果表明，通过重叠两个相反对称的 Mie 模式可以实现完美的吸收，每个模式的理论最大值为 50 %处于各自的临界耦合状态。吸收还显示出偏振无关和角度不敏感的鲁棒性。这项工作与设计理念一起，为实现高效半导体器件（包括光发射器、调制器、探测器和传感器）开辟了巨大的机遇。