Multisubband electron transport in GaAs-AlxGa1-x As quantum wells

A general transport model for the conduction of electrons in square GaAs-Al_xGa_1-xAs quantum wells is described. The electrons are treated as an ideal two-dimensional system, while lattice scattering is treated through a regular three-dimensional phonon system. The electronic conduction of the well is considered to be a superposition of the conduction arising from the sheet carrier density of each of the individual subbands with allowance for scattering of carriers between different subbands. Balance equations for carrier number, momentum, and energy density are derived for each subband, and the relaxation times are calculated for the more common scattering processes. This balance-equation transport model provides a detailed description of the dynamics of a quantum well for the case where the subband structure is important, or where intersubband transitions or optical generation processes repopulate one subband at the expense of the others