Broadband Photoresponse Enhancement by Band Engineering in Sb-Doped MnBi2Te4

Topological materials have attracted considerable attention for their potential in broadband and fast photoresponses, particularly in the infrared regime. However, the high carrier concentration in these systems often leads to rapid recombination of photogenerated carriers, limiting the photoresponsivity. Here, we demonstrate that Sb doping in MnBi₂Te₄ effectively reduces carrier concentration and suppresses electron–hole recombination, thereby significantly improving the optoelectronic performance across the visible to mid-infrared spectra. The optimally doped Mn(Bi_0.82Sb_0.18)₂Te₄ photodetector achieves a responsivity of 3.02 mA W^–1 with a response time of 18.5 μs at 1550 nm, and 0.795 mA W^–1 with a response time of 9.0 μs at 4 μm. These values represent nearly 2 orders of magnitude improvement compared to undoped MnBi₂Te₄. Our results highlight band engineering as an effective strategy to enhance the infrared performance of topological material-based photodetectors, opening new avenues for high-sensitivity infrared detection.