Ultrahigh broadband photoresponse of SnO 2 nanoparticle thin film/SiO 2 /p-Si heterojunction.

The SnO2 /Si heterojunction possesses a large band offset and it is easy to control the transportation of carriers in the SnO2 /Si heterojunction to realize high-response broadband detection. Therefore, we investigated the potential of the SnO2 nanoparticle thin film/SiO2 /p-Si heterojunction for photodetectors. It is demonstrated that this heterojunction shows a stable, repeatable and broadband photoresponse from 365 nm to 980 nm. Meanwhile, the responsivity of the device approaches a high value in the range of 0.285-0.355 A W-1 with the outstanding detectivity of ∼2.66 × 1012 cm H1/2 W-1 and excellent sensitivity of ∼1.8 × 106 cm2 W-1 , and its response and recovery times are extremely short (<0.1 s). This performance makes the device stand out among previously reported oxide or oxide/Si based photodetectors. In fact, the photosensitivity and detectivity of this heterojunction are an order of magnitude higher than that of 2D material based heterojunctions such as (Bi2 Te3 )/Si and MoS2 /graphene (photosensitivity of 7.5 × 105 cm2 W-1 and detectivity of ∼2.5 × 1011 cm H1/2 W-1 ). The excellent device performance is attributed to the large Fermi energy difference between the SnO2 nanoparticle thin film and Si, SnO2 nanostructure, oxygen vacancy defects and thin SiO2 layer. Consequently, practical highly-responsive broadband PDs may be actualized in the future.