INTERSUBBAND SCATTERING IN A 2D ELECTRON-GAS

A new technique, using the absolute amplitude of the low-field Shubnikov-de Haas oscillations, is presented which allows the direct measurement of inter-subband scattering in 2D heterojunction structures. When applied to a heterojunction with two subbands occupied the technique is used to show that inter-subband scattering is independent of temperature between 1 and 4 K. In agreement with previous reports frequency and amplitude intermodulation, which increases with temperature, is also observed. This is attributed to mixing, by thermal or impurity damping, between the two sets of oscillations in the Fermi energy. This explanation is supported by a model calculation which reproduces the features of the experimental results.