COMPARATIVE CYCLOTRON-RESONANCE AND LUMINESCENCE STUDY OF PHOTOEXCITED PARTICLES IN MIXED TYPE-I-TYPE-II GAAS ALAS MULTIPLE-QUANTUM WELLS/

hWe report on the photoluminescence (PL) and photoinduced microwave ab sorption (PMA) of the elementary excitations in GaAs/AlAs undoped quan tum wells (QW's) in the temperature range 2<T-L<30 K. Mixed type-I-typ e-II QW's are used, since separate two-dimensional electron and hole g ases are formed (in the wide and narrow QW's, respectively) by photoex citation with densities in the range 10(9)<n(e) less than or equal to 5 X 10(10) cm(-2). The PL spectra show transitions due to (e1:hh1)1S e xcitons (X) and [(e1:hh1)1S+e] negatively charged excitons (X-). The P MA dependence on magnetic held that is applied perpendicularly to the QW planes shows cyclotron resonances (CR) due to electrons and X- in t he wide wells and heavy holes in the narrow wells. The CR traces are a nalyzed and yield the cyclotron effective mass, momentum relaxation ra te, and relative density of the charged particles. The PL and PMA spec tra are found to correlate well when observed at the same temperature and microwave power. The electron and X- masses and relative intensiti es are analyzed in terms of weak in-plane particle localization. It is found that, at low temperatures, a large fraction of the electrons an d X- are localized by interface potential fluctuations.