of device junctions such as metal oxide semiconductor (MOS) p-and n-channel, tunneling p-or n-junction, and Schottky junction, etc., can be crafted and fabricated separately. In the post-silicon era, newgeneration van der Waals materials such as two-dimensional (2D) semiconductors have received extensive attention and research due to their practical advantages of smooth surface, [1,2] high mobility, [3] ultrathin, [4] flexibility, [5,6] in-plane structural and optical anisotropy, [7][8][9][10] thickness-dependent carrier conduction, [11] thickness tunable bandgap, [12,13] and abundance of direct band-edge excitons. [14,15] Among them, transition metal dichalcogenides (TMDs), including four popular members, MoS 2 , MoSe 2 , WS 2 , and WSe 2 , have been vigorously studied and have potential capabilities in practical semiconductor device applications such as field-effect transistors, [16] bipolar junction transistors, [17,18] phototransistors, [19] and light-emitting diodes (LEDs), [20] etc., due to their high environmental stability and the flexibility on thickness tuning bandgaps. The growth of p-and n-type materials in TMDs layers may be a key issue for the development of various p-n junction devices in 2D semiconductor technology. However, to date, the synthesis of p-type layered TMDs is still challenging, and even some proposals have been made related to Nbdoped p-MoSe 2 , [21] Nb-doped p-MoS 2 , [22] oxygen plasma doped p-MoS 2 , [23] and nitrogen-induced p-WS 2 , [24] etc., the information on the ideal dopants for forming p-type TMDs with controllable carrier concentration and good stability is still insufficient and needs to be further explored. Nowadays, many TMD bipolar p-n junction devices and LEDs typically operate in gate-controlled p-and n-type with a lateral junction, [20,25,26] and a large number of vertically stacked 2D layered devices are still fabricated as heterostructures and heterojunctions [17,18] because of the lack of van der Waals stacked p-n homojunction.Compared to conventional MoS 2 , MoSe 2 , WS 2 , and WSe 2 dichalcogenides, rhenium diselenide (ReSe 2 ) is also an important member of the TMD-family 2D semiconductors, which crystallizes in a specific distorted CdI 2 -type layered structure of triclinic symmetry (space group P1). [27,28] Dissimilar to that the MoS 2 group has a uniform and isotropic layer plane in generally two-layer hexagonal or three-layer rhombohedral form, the structural distortion in the CdI 2 -type (i.e., 1T′) ReSe 2 layer may cause by a specific d 3 nonbonding Re-Re interaction and which The formation of p-or n-type material via impurity doping should be crucial and essentially prior to the establishment of junction devices in semiconductor processing. Especially in a 2D transition-metal dichalcogenide (TMD), dopant selection for growing p-and n-type TMD semiconductors may suffer much higher difficulty and complexity than conventional Si and III-V compounds owing to the complicated valences occurred in transition metals. Different amount of chromium doped in ReSe ...

Modern infrared (IR) microscopy, communication, and sensing systems demand control of the spectral characteristics and polarization states of light. Typically, these systems require the cascading of multiple filters, polarization optics, and rotating components to manipulate light, inevitably increasing their sizes and complexities. Here, we report two-terminal mid-infrared (mid-IR) emitters, in which tuning the polarity of the applied bias can switch their emission peak wavelengths and linear polarization states along two orthogonal orientations. Our devices are composed of two back-to-back p–n junctions formed by stacking anisotropic light-emitting materials, black phosphorus and black arsenic–phosphorus with MoS2. By controlling the crystallographic orientations and engineering the band profile of heterostructures, the emissions of two junctions exhibit distinct spectral ranges and polarization directions; more importantly, these two electroluminescence (EL) units can be independently activated, depending on the polarity of the applied bias. Furthermore, we show that when operating our emitter under the polarity-switched pulse mode, the time-averaged EL exhibits the characteristics of broad spectral coverage, encompassing the entire first mid-IR atmospheric window (λ: 3–5 μm), and electrically tunable spectral shapes.

Modern infrared (IR) microscopy, communication, and sensing systems demand control of the spectral characteristics and polarization states of light. Typically, these systems require the cascading of multiple filters, polarization optics and rotating components to manipulate light, inevitably increasing their sizes and complexities. Here, we report two-terminal mid-infrared (mid-IR) emitters with electrically controllable spectral and polarization properties. Our devices are composed of two back-to-back p-n junctions formed by stacking anisotropic light-emitting materials, black phosphorus and black arsenic-phosphorus with MoS2. By controlling the crystallographic orientations and engineering the band profile of heterostructures, the emissions of two junctions exhibit distinct spectral ranges and polarization directions; more importantly, these two electroluminescence (EL) units can be independently activated, depending on the polarity of the applied bias. Furthermore, we show that when operating our emitter under the polarity-switched pulse mode, its EL exhibits the characteristics of broad spectral coverage, encompassing the entire first mid-IR atmospheric window (λ: 3–5 µm), and electrically tuneable spectral shapes. Our results provide the basis for developing groundbreaking technology in the field of light emitters.