Linewidth and dephasing of THz-frequency collective intersubband transitions in a GaAs/AlGaAs quantum well

Terahertz-frequency intersubband (ISB) transitions in semiconductor quantum wells are of interest due to the potential for making devices that operate at THz frequencies, and the influence of many-body interactions on the intersubband dynamics. We present measurements of the linear absorption linewidth of ISB transitions in a single 40 nm delta-doped GaAs/Al0.3Ga0.7As square quantum well, with a transition energy of order 10 meV (3 THz). Separate back- and front-gates allow independent control of charge density (0.1–View the MathML source) and DC bias (−2.5–View the MathML source). A picture of scattering of the intersubband plasmon into single-particle excitations qualitatively explains the DC bias dependence of the line-width data.