Ultrahigh Performance UV Photodetector by Inserting an Al2O3 Nanolayer in NiO/n-Si

Abstract

Ultraviolet (UV) photodetectors have gained much attention due to their numerous important applications ranging from environmental monitoring to space communication. To date, most p-NiO/n-Si heterojunction photodetectors (HPDs) exhibit poor UV responsivity and slow response. This is mainly due to a small valence band offset (ΔE_V) at the NiO/Si interface and a high density of dangling bonds at the silicon surface. Herein, an UV HPD consisting of NiO/Al₂O₃/n-Si is fabricated using magnetron sputtering technique. The HPD has a large rectification ratio of 2.4 × 10⁵. It also exhibits excellent UV responsivity (R) of 15.8 A/W at −5 V and and detectivity (D*) of 1.14 × 10¹³ Jones at −4 V, respectively. The excellent performance of the HPD can be attributed to the defect passivation at the interfaces of the heterojunction and the efficient separation of photogenerated carriers by the Al₂O₃ nanolayer. The external quantum efficiency (EQE) of the HPD as high as 5.4 × 10³%, hence implying a large optical gain due to carrier proliferation resulting from impact ionization. Furthermore, the ultrafast response speed with a rise time of 80 µs and a decay time of 184 µs are obtained.