Operation of resonant-tunneling diodes beyond resonant-state-lifetime limit

We show, first, that the charge relaxation (response) time of resonant-tunneling diode (RTD) can be significantly shorter or longer than the resonant-state lifetime, depending on RTD operating point and RTD parameters. Coulomb interaction between electrons is responsible for the effect. Second, it is also demonstrated that the operating frequencies of RTDs are limited neither by resonant-state lifetime nor by relaxation time; particularly in the RTDs with heavily doped collector, the differential conductance can stay negative at the frequencies far beyond the limits imposed by the time constants. We provide experimental evidences for both effects. (c) 2007 American Institute of Physics.