Photoresponse study of MWCNTS/insulator/n-type Si/insulator/metal heterostuctures as a function of the density of MWCNTs layer

In this work devices based on a MWCNTs-Si heterojunction were realized growing MWCNTs, by chemical vapour deposition, on an n-type Si substrate with the top and bottom surfaces covered by 140 nm thick Si₃N₄ layers. Two metal contacts, realized on top and back Si surface, were used to perform I-V measurements of the vertical heterostructure. The photocurrent behaviour, obtained by light illumination, was studied as a function of the thickness of MWCNTs layer. A planar quantum efficiency map of the device was obtained by I-V measure when the active area of the device, was rastered by 1 mm diameter light spot. The thickness reduction of the MWCNTs was realized by adhesive tape.

We found that the photocurrent intensity increased when the density of the MWCNTs layer was decreased.

To check the substrate coverage by MWCNTs, scanning electron microscope images was taken.