  We report the detection of the cyclotron(CR) and magneto-plasmon(MPR)
resonances near the Fermi surface of high-mobility 2DES, by microwave
photoresistance measurements. We observe large amplitude photoresistance
oscillations originating from higher-order CR, transitions between non-adjacent
Landau levels. Such transitions are drastically enhanced in low magnetic field
as compared to those previously known in the high field limit. The scattering
time of the CR is found to be nearly one order of magnitude higher than that of
Shubnikov-de-Haas oscillations. Finally, distinct photoresistance peaks are
observed in addition to the CR features. These are identified as resonances of
the low-frequency MP modes at a cut-off wavelength determined by the width of
the 2DES sample.
