Farhyphen;infrared pumphyphen;probe measurements of the intersubband lifetime in an AlGaAs/GaAs coupledhyphen;quantum well

摘要

We report pumphyphen;andhyphen;probe measurements of the electron intersubband lifetime (T1) in an AlGaAs/GaAs heterostructure using a picosecond pulsed farhyphen;infrared laser. The subband spacing (11 meV) is less than the opticalhyphen;phonon energy. Timehyphen;resolved measurements yield intersubband lifetimes ranging fromT1=1.1plusmn;0.2 ns toT1=0.4plusmn;0.1 ns depending on measurement conditions. Results are in agreement with previous lifetime measurements on the same sample using continuous excitation at intensities le;1 W/cm2. The steadyhyphen;state measurements yielded shorter lifetimes at high excitation intensities, possibly due to carrier heating leading to intersubband scattering by optical phonon emission. copy;1996 American Institute of Physics.