Does the quasibound-state lifetime restrict the high-frequency operation of resonant-tunnelling diodes?

We have shown, firstly, that the response time (τ resp ) of the double-barrier resonant-tunnelling diode (RTD) can be much smaller as well as much larger than the quasibound-state lifetime in the quantum well (τ dwell ). Secondly, the real part of the RTD conductance can be negative and large at the frequencies higher than the reciprocal τ dwell in the RTDs with a heavily doped collector without spacer layers. The Coulomb interaction of the electrons in the quantum well with emitter and collector is responsible for the effects. A simple analytical expression for the impedance of the RTD has been derived and an equivalent circuit has been proposed.