Spectral linewidth broadening of the zeroth order Stark ladder transition in [formula omitted] superlattices with ultrathin barriers

Abstract

Photocurrent spectra of a series of monoperiodic GaAs AlAs superlattices with a fixed well width of 22 monolayers (ML) and different ultrathin barriers (2–4 ML) are investigated as a function of bias voltage at 16 K. Under applied high electric fields, it is found that the observed linewidth of the leading 0th order Stark ladder transition significantly increases with decreasing the barrier thickness. That is, the linewidth for the superlattice with thinner barriers is found to be much broader than that with the thick barrier SL which is basically determined by the usual inhomogeneous broadening. This enhancement of the spectral linewidth is due to a lifetime broadening of the quasi-bound Stark localized states. Simple calculations for the double-barrier quantum well structures give an electron level broadening in agreement with the experimental results.