Self-doped p–n junctions in two-dimensional In2X3 van der Waals materials†
With the advent of two-dimensional materials, it is now possible to realize p–n junctions at the ultimate thickness limit. However, the performance of p–n junctions significantly degrades as their thicknesses approach the nanoscale and the conventional fabrication processes, such as implantation and doping, become invalid. Here, using first-principles calculations, we report a novel strategy to realize self-doped p–n junctions in two-dimensional materials. By stacking triple-layer In2X3 (X = S, Se), an atomically thin p–n junction forms naturally without any additional modulation involved, which is attributed to the asymmetric structure-induced self-doping. In addition, such self-doped p–n junctions are also obtained when sandwiching single-layer and double-layer In2S3 in-between graphene layers. More interestingly, the outmost layers in all these systems become metallic due to the self-doping, achieving natural low-resistance contact. This work illustrates a straightforward method for developing more effective electronic and optoelectronic nanodevices.