The investigation of Al-doped ZnO as an electron transporting layer for visible-blind ultraviolet photodetector based on n-ZnO nanorods/p-Si heterojunction

An n-ZnO nanorods/p-Si heterojunction photodetector with Al-doped ZnO (AZO) as an electron transporting layer was fabricated. The heterojunction with 20 nm AZO film showed a better characteristic than that of the device without AZO, and it displays a rectification ratio of 8470 at ±3 V and a turn-on voltage of 1.8 V. Also, based on spectral responsivity measurement, the device with AZO coating showed higher responsivity and better visible-blind detectivity than those without AZO, and the peak responsivity of the photodetector with AZO was as high as ~0.49 A/W at 354 nm. Furthermore, the photodetector with AZO layer showed a bigger UV–visible responsivity ratio (R354 nm / R546 nm) than that of the photodetector without AZO coating at −2 V. The role of AZO layer was illustrated through energy band theory and the electron transport mechanism.