We have calculated electron–optical-phonon scattering rates in ultrathin GaAs/${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As alloy quantum-well systems of finite depth, based on a fully microscopic lattice dynamics approach for the phonon spectra. A pseudo-unit-cell model is utilized to calculate the lattice-dynamical properties of the ${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As alloy system together with the two-parameter Keating potential and the long-range Coulomb potential between ions. The polar interactions of quantum confined electrons with GaAs- and AlAs-like optical modes are presented for both intrasubband and intersubband transitions, and the comparison with other theoretical calculations made. Good agreement is obtained for the 1→1 and 2→1 transition rates between the microscopic pseuso-unit-cell model and a macroscopic two-pole dielectric continuum model.

• Received 2 September 1994

DOI:https://doi.org/10.1103/PhysRevB.51.7046