Graphene vertical cascade interband terahertz and infrared photodetectors

We propose and evaluate vertical cascade terahertz and infrared photodetectors based on multiple-graphene-layer (GL) structures with thin tunnel barrier layers (made of tungsten disulfide or related materials). The operation of photodetectors is associated with the cascaded radiative electron transitions from the valence band in the GLs to the conduction band in the neighboring GLs (interband and inter-GL transitions). We calculate the spectral dependencies of the responsivity and detectivity for vertical cascade interband GL photodetectors (I-GLPDs) with different numbers of GLs and doping levels at different bias voltages in a wide range of temperatures. We show the possibility of effectively manipulating the spectral characteristics with the applied voltage. The spectral characteristics also depend on the GL doping level, which opens up the prospect of using I-GLPDs in multicolor systems. The advantages of the I-GLPDs under consideration are associated with their sensitivity to normal incident radiation, the weak temperature dependence of the dark current, as well as their high speed operation. A comparison of the proposed I-GLDs with quantum-well intersubband photodectors demonstrates the superiority of the former, including having better detectivity at room temperature and a higher speed. The vertical cascade I-GLDs can also surpass the lateral p-i-n GLDs in terms of speed.