We report the direct observation of a bottleneck in electron cooling in wide GaAs quantum wells. Intersubband lifetimes t and their dependence on intensity, lattice temperature TL, and well width have been measured using a ps excite-probe technique in wells with subband separation less than the longitudinal optical (LO) phonon energy. Above an electron temperature of about Te=35 K the lifetime depends on Te and is determined by LO-phonon emission. Below this bottleneck temperature acoustic phonons dominate the plasma cooling. An energy balance model of these interactions, with no adjustable parameters, gives good agreement with our results. At electron temperatures below 35 K we determine t=500 and 200 ps for samples of subband energy 19.5 and 26.6 meV, respectively.
|Number of pages||6|
|Journal||Physical Review B: Condensed Matter and Materials Physics|
|Publication status||Published - 15 Feb 1997|