Figure 8
Photoresponsivity and cut-off wavelength measurements.
(a) Variation of photoresponsivity with bias voltages for three types of channels: a bare semi-insulating Si (111) substrate and n-GaN NRs grown on the same substrate with and without a graphene layer. (b) Using various optical power densities of the light source, the photocurrent at different bias was measured for the n-GaN NR-graphene hybrid structure. (c) The photocurrent Ip measured at various optical power densities increased linearly, which was attributed to a reduced density of trap levels in the photoconductive channel; the exponent x in the power law has a high value of approximately 0.94. This measurement was performed with the bias fixed at 2.0 V. (d) The spectral photoresponse measurement reveals a cut-off wavelength of 380 nm for the n-GaN NR-graphene hybrid structure.
