Broadband and photovoltaic THz/IR response in the GaAs-based ratchet photodetector
Peng Bai, Xiaohong Li, Ning Yang, Weidong Chu, Xueqi Bai, Siheng Huang, Yueheng Zhang, Wenzhong Shen, Zhanglong Fu, Dixiang Shao, Zhiyong Tan, Hua Li, Juncheng Cao, Lianhe Li, E. H. Linfield, Yan Xie, Ziran Zhao
Abstract
High-performance broadband infrared (IR)/terahertz (THz) detection is crucial in many optoelectronic applications. However, the spectral response range of semiconductor-based photodetectors is limited by the bandgaps. This paper proposes a ratchet structure based on the GaAs/Al x Ga 1− x As heterojunction, where the quasi-stationary hot hole distribution and intravalence band absorption from light or heavy hole states to the split-off band overcome the bandgap limit, ensuring an ultrabroadband photoresponse from near-IR to THz region (4 to 300 THz). The peak responsivity of the proposed structure can reach 7.3 A/W, which is five orders of magnitude higher than that of the existing broadband photon-type detector. Because of the ratchet effect, the proposed photodetector has a bias-tunable photoresponse characteristic and can operate in the photovoltaic mode with a broad photocurrent spectrum (18 to 300 THz). This work not only demonstrates a broadband photon-type THz/IR photodetector but also provides a method to study the light-responsive ratchet.