Photo-Induced Effects in Graphene Channels When Interfaced with Quantum Dot Array

Field effect transistors with graphene channels were interfaced with semiconductor quantum dot (QD) array.  Electrical characteristics and opto-electronic behaviour of the elements were assessed.  Relative photo-resistance (the difference in channel resistances under dark and under light conditions and normalized by the channel’s resistance) was observed as a function of drain-source potential.

Graphene – a mono layer thick crystalline form of carbon - portrays high conductivity, chemical inertness, mechanical robustness and unusual dispersion relations [1].  Characteristics of free-standing, mono and bi-layer graphene have been studied when deposited over nano-pore array of anodized aluminum oxide (AAO) substrate.  One may postulate that QDs, filling the pores, will have a profound effect on the graphene channel.  Such arrangement led to the realization of the first visible surface plasmon laser [2]. 

The field effect transistors (FET) were fabricated on oxidized silicon wafers.  They were composed of graphene channels and two metal electrodes, used as drain and source electrodes.  The silicon wafer served as a back gate electrode.  Contacts to the graphene were found Ohmic.  Aluminum, was deposited on the oxidized silicon wafer and was anodized according to our previous recipe.  Core-shell semiconductor CdSe/ZnS QDs were imbedded in the anodized aluminum pores and the semi-transparent graphene was deposited on top of the anodized layer.

Unlike ordinary graphene channels, the current between the drain and source, Ids, decreased as a function of gate bias, Vgs.  When illuminated by a 50 mW/cm2 white light source, the channel exhibited a clear relative differential resistance at Vds=0.3 V.  This behavior was attributed to a negative differential resistance effect. 

[1] A. C. Ferrari, J. C. Meyer, V. Scardaci, M. Lazzeri, F. Mauri, S. Piscance, D. Jiang, K. S. Novoselov, S. Roth and A. K. Geim, “Raman Spectrum of Graphene and Graphene Layers”, Phys. Rev. Lett., 97, 187401 (2006).

[2] R. Li, A. Banerjee and H. Grebel, “The possibility for surface plasmon lasers”, Optics Express, 17, 1622-1627 (2009).

[3] S. W. Lee, A. Kornblit, D. Lopez, S. V. Rotkin. A. Sirenko, H. Grebel, “Negative Differential Resistance: Gate Controlled and Photoconductance Enhancement in Carbon Nanotube Intra-connects”, Nano Letters, DOI: 10.1021/nl803036a (2009).