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A highly tunable photoelectric response of graphene field-effect transistor with lateral P–N junction in channel

This paper reports a highly tunable photoelectric response of graphene field-effect transistor (GFET) with lateral P–N junction in channel. The poly(sulfobetaine methacrylate) (PSBMA) provides strong N-type doping on graphene due to the dipole moment of pendent groups after ultraviolet annealing in high vacuum. A lateral P–N junction is introduced into the channel of the GFET by partially covering the graphene channel with PSBMA. With such P–N junction in the channel, the GFET exhibits a highly tunable photoelectric response over a wide range of exciting photon wavelength. With a lateral P–N junction in the channel, the polarity of photocurrent (I ph) of the GFET switches three times as the back-gate voltage (V BG) scan over two Dirac-point voltages. The underlying physical mechanism of photoelectric response is attributed to photovoltaic and photo-induced bolometric effect, which compete to dominating I ph at various V BG. This provides a possible strategy for designing new phototransistors or optoelectronic device in the future.