Quasi Resonant Tunneling Lifetime in Multibarrier System Under the Action of Electricfield

Abstract

In the unbiased periodic MBS the resonant tunneling corresponds to unit transmission coefficient across the structure. With the application of low and moderate dc-electric fields, the tunneling energy spectrum (quasiresonant) of the MBS gets Stark shifted and the transmittance for some of the resonance-type peaks gets lowered compared to those in the field-free case due to gradual localization of wave functions which can be explained using bending band picture. In this context for a biased MBS, the carrier lifetime under quasiresonant condition can be termed as quasiresonant tunneling lifetime (QRTL). The QRTL is the most important parameter that has to be determined for realizing the tunable quantum cascade laser [3-5] on the basis of Wannier-Stark ladder (WSL). The theoretical investigations of lifetime has been reported for the double-barrier systems (DBSs) [6-11], MBSs [12- 13], and SLs [14-17] in the absence of external dc-electric field and also for the dcbiased quantum wells [18-19], DBSs [20], and SLs [21]. But none of them has addressed the response of QRTL to the applied field for individual quasiresonant states in an electrically biased MBS, which would be the key issue in modeling highspeed RT devices. We address these aspects in the following sections.