  We present a detailed theoretical investigation on the radiation induced
giant magnetoresistance oscillations recently discovered in high-mobility
two-dimensional electron gas. Electron interactions with impurities, transverse
and longitudinal acoustic phonons in GaAs-based heterosystems are considered
simultaneously. Multiphoton-assisted impurity scatterings are shown to be the
primary origin of the resistance oscillation. Based on the balance-equation
theory developed for magnetotransport in Faraday geometry, we are able not only
to reproduce the observed period, phase and the negative resistivity of the
main oscillations, but also to predict the secondary peak/valley structures
relating to two-photon and three-photon processes. The dependence of the
magnetoresistance oscillation on microwave intensity, the role of dc bias
current and the effect of elevated electron temperature are discussed.
Furthermore, we propose that the temperature-dependence of the resistance
oscillation stems from the growth of the Landau level broadening due to the
enhancement of acoustic phonon scattering with increasing lattice temperature.
The calculated temperature-variation of the oscillation agrees well with
experimental observations.
