High-sensitivity and self-driven photodetectors based on Ge-CdS core-shell heterojunction nanowires via atomic layer deposition

摘要

Core-shell p-n heterojunction nanowires (NWs) hold great promise for optoelectronic applications due to the large effective junction area and minimized carrier recombination. However, the rational design and synthesis of core-shell heterojunction NWs are hindered by the complex fabrication process and the potential damage to core NWs during shell deposition. Herein, we demonstrated the fabrication of Ge-CdS core-shell heterojunction NWs via a facile atomic layer deposition (ALD) technique. The ALD technique allowed the conformal deposition of polycrystalline CdS shells on single-crystalline Ge NWs with high uniformity and controllable thickness. The heterojunction NWs exhibited excellent diode characteristics, with a pronounced photoresponse under light illumination. Significantly, owing to the existence of a built-in electric field, the heterojunctions could serve as self-driven photodetectors, with a high photosensitivity of 18 000%, which is remarkably much better than previous reports on Ge NW photodetectors. The complementary bandgaps of Ge and CdS also ensured that the device had a capability for broadband detection from visible to infrared light. This study represents an important advance in fabricating core-shell heterojunction NWs for high-performance optoelectronic applications.