Influence of Doping Concentration on Intersubband Relaxation in Modulation‐Doped Quantum Well Structures

Abstract
Intersubband scattering in multiple n‐type modulation‐doped quantum well structures is studied by an infrared bleaching technique at room temperature. The repopulation of the lowest subband of the well is directly observed. In GaAs/Al0.35Ga0.65As quantum wells (thickness 5.9 nm) an increase of the relaxation time from 4 to 7.5 ps is found for increasing doping concentrations from 3.2 × 1011 to 1.4 × 1012 cm−2. Carrier transfer between the wells and barrier states is discussed as a process which determines the relaxation time.