  We propose and analize a graphene tunneling transit time device based on a
heterostructure with a lateral p-i-n junction electrically induced in the
graphene layer by the applied gate voltages of different polarity. The depleted
i-section of the graphene layer (between the gates) serves as both the
tunneling injector and the transit region. Using the developed device model, we
demonstrate that the ballistic transit of electrons and holes generated due to
interband tunneling in the i-section results in the negative ac conductance in
the terahertz frequency range, so that the device can serve as a terahertz
oscillator.
