Wavelength-selective photodetectors with high quantum efficiency using an optical blocking layer and a field-induced junction on a silicon nanowire

Abstract

Crystalline silicon nanowires (c-SiNWs) have unique optical characteristics that enable tuning of their spectral response. However, real-world applications of c-SiNWs as multispectral photodetectors are still hampered by their low selectivity and low quantum efficiency (<30%). The primary obstacles include the broad-spectrum light absorption of the bottom crystalline silicon (c-Si) substrate underneath the c-SiNWs and the difficulties in forming appropriate p-n junctions on c-SiNWs. In this study, an optical blocking layer was applied to block light absorption in the bottom c-Si substrate, and atomic-layer deposition-based Al2O3 was employed to form a dopant-free p-n junction on diameter-controlled c-SiNWs. Consequently, the maximum external quantum efficiency (EQE) of the fabricated photodetector is 77.4% with remarkable wavelength selectivity. This work removes major stumbling blocks for the use of c-SiNWs as selective light spectral band-pass photodetectors.