Thin Phophorus‐Oxide‐Assisted Electrically Pumped Mid‐Infrared Light Emission in a Twisted Black Phosphorus Structure with Polarization Switching

ABSTRACT Efficient and polarization‐switchable on‐chip mid‐infrared light sources are desirable for portable and miniaturized systems for applications in gas sensing, free‐space optical communications, and imaging. The polarization‐switchable function can offer a new information dimension for signal processing. Black phosphorus (BP), with perfect linear dichroism, high internal quantum efficiency, and a narrow bandgap of 0.3 eV, is a promising candidate for polarization‐switchable on‐chip mid‐infrared light sources. Here, we demonstrate an electrically pumped, robust, and polarization‐switchable mid‐infrared light emission in a twisted BP structure. Through introducing an oxidized phosphorus interface between the top and bottom BP layers to engineer the energy band alignment and controlling BP crystalline orientations, the mid‐infrared emission can be electrically pumped, and light polarization states can be switched between top and bottom BP layers by simply changing the polarity of the applied bias. The phenomenon can be observed in a wide twisted angles up to 90°. Delicate peak external quantum efficiencies of 0.28% and 4.87% are achieved at 300 and 80 K, respectively. Moreover, an optical logic operation strategy based on the polarization‐switchable light emission property is demonstrated.