  In this study we used selectively-doped GaAs/AlAs heterostructure to
fabricate a high-mobility two-subband electronic system with substantially
different concentration of electrons in subbands. We observe microwave
photoresistance at high numbers of magneto-intersubband oscillations (MISO).
The system under study demonstrates microwave-induced resistance oscillations
(MIRO) and MISO interference. MIRO in the studied two-subband system appear in
lower magnetic fields comparing to MISO. This is an indication of some unknown
mechanism that exists in the two-subband system and is responsible for MISO
amplitude damping in low magnetic fields, while it does not affect the MIRO
amplitude. Zero resistance states (ZRS) appear in the system under study under
microwave irradiation in the narrow range of magnetic fields near the MISO
maximum.
