Far-infrared pump-probe measurements of the intersubband lifetime in an AlGaAs/GaAs coupled-quantum well

Abstract

We report pump‐and‐probe measurements of the electron intersubband lifetime (T₁) in an AlGaAs/GaAs heterostructure using a picosecond pulsed far‐infrared laser. The subband spacing (11 meV) is less than the optical‐phonon energy. Time‐resolved measurements yield intersubband lifetimes ranging from T₁=1.1±0.2 ns to T₁=0.4±0.1 ns depending on measurement conditions. Results are in agreement with previous lifetime measurements on the same sample using continuous excitation at intensities ≤1 W/cm². The steady‐state measurements yielded shorter lifetimes at high excitation intensities, possibly due to carrier heating leading to intersubband scattering by optical phonon emission.