Complex-energy analysis of intrinsic lifetimes of resonances in biased multiple quantum wells

The electric-field-dependent intrinsic lifetimes of resonances in biased multiple qunatum wells are studied by using a complex-energy analysis based on an Airy-function transfer-matrix description of tunneling. Special attention is paid to the case when at some particular electric field two resonances belonging to different quantum wells resonantly align in energy. Two different characteristic behaviors were found in such electric-field sweeps: Long-lived resonances typically exhibit an anticrossing of their quasieigenenergies and a corresponding crossing of their lifetimes, usually associated with large changes in these lifetimes over many orders of magnitude, while short-lived resonances feature a crossing of their quasieigenenergies and an anticrossing of their lifetimes with less variation in these lifetimes. The parameters relevant for these two different regimes are discussed, and a simple model is derived to describe the crossover between these regimes.