Single‐Crystalline Lateral <i>p</i> ‐SnS/ <i>n</i> ‐SnSe van der Waals Heterostructures by Vapor Transport Growth with In Situ Bi Doping

Junctions between p ‐ and n ‐doped semiconductors are ubiquitous in modern electronic devices and circuits. However, the tendency toward ‘natural’ defect doping (i.e., a fixed majority carrier polarity) has made the realization of pn ‐junctions between 2D/layered chalcogenide semiconductors challenging. Here, the formation of high‐quality, electrically active lateral junctions between Bi‐doped n ‐type SnSe and p ‐type SnS is demonstrated via a two‐step growth process, building on the successful integration of single‐crystalline ( p ‐type) SnSe and SnS in multilayer lateral heterostructures. The growth of single‐crystalline n ‐type SnSe:Bi flakes is established using vapor transport with in situ Bi doping. Subsequent SnS growth yields heterostructures between the SnSe:Bi seeds and a laterally stitched edge band of p ‐type SnS. Combined optical microscopy, Raman spectroscopy, scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, and transmission electron microscopy demonstrate the formation of purely lateral SnS/SnSe:Bi heterostructures from standing, Bi‐doped SnSe seeds on mica substrates. Electron beam induced current measurements on individual heterostructures provide evidence for successful n ‐type doping of the SnSe:Bi seeds and the formation of an electrically active pn ‐junction at the lateral SnS/SnSe interface. The realization of sharp lateral pn ‐junctions in single‐crystalline layered chalcogenide semiconductors paves the way for applications in electronics, photovoltaics, thermoelectrics, etc.