Persistent photocurrent in amorphous chalcogenides

Extrinsic Photoconduction Induced Short-Wavelength Infrared Photodetectors Based on Ge-Based Chalcogenides

2D layered photodetectors have been widely researched for intriguing optoelectronic properties but their application fields are limited by the bandgap. Extending the detection waveband can significantly enrich functionalities and applications of photodetectors. For example, after breaking through bandgap limitation, extrinsic Si photodetectors are used for short-wavelength infrared or even long-wavelength infrared detection. Utilizing extrinsic photoconduction to extend the detection waveband of 2D layered photodetectors is attractive and desirable. However, extrinsic photoconduction has yet not been observed in 2D layered materials. Here, extrinsic photoconduction-induced short-wavelength infrared photodetectors based on Ge-based chalcogenides are reported for the first time and the effectiveness of intrinsic point defects are demonstrated. The detection waveband of room-temperature extrinsic GeSe photodetectors with the assistance of Ge vacancies is broadened to 1.6 µm. Extrinsic GeSe photodetectors have an excellent external quantum efficiency (0.5%) at the communication band of 1.31 µm and polarization-resolved capability to subwaveband radiation. Moreover, room-temperature extrinsic GeS photodetectors with a detection waveband to the communication band of 1.55 µm further verify the versatility of intrinsic point defects. This approach provides design strategies to enrich the functionalities of 2D layered photodetectors.

Synthesis of periodic hexagonal surfactant templated platinum tin tellurides: narrow band gap inorganic/organic composites

In this work we report the synthesis and characterization of a new nanostructured platinum/tin/telluride inorganic/surfactant composite. The material is synthesized from soluble SnTe(4)(4-) clusters and is shown to have well-defined nanometer scale periodicity along with unique optical properties. Small-angle X-ray scattering indicates that the material forms with a 2D hexagonal honeycomb structure, which is size tunable based on surfactant tail length. Multinuclear EXAFS is used as a probe of local order in these materials. The results indicate that the tetrahedral SnTe(4) unit dimerizes during assembly, and these clusters are coordinated to square planar platinum ions. Near-IR/visible reflectance spectroscopy indicates that the material is a narrow band gap semiconductor with a band gap of 0.8 eV. The extension of the ideas of surfactant templating to a narrow band gap semiconductor opens up the exciting potential for future optoelectronic applications.