Differential analysis of Landau levels associated with conduction subband of InGaAs/InAlAs multi-quantum wells in magneto-photoluminescence study

Electronic states of two-dimensional conduction subbands (CSs) accompanied by complex exciton and impurity states, caused by modulation-doping in InGaAs/InAlAs quantum wells (QWs), were studied by magneto-photoluminescence (MPL) at 1.4 K below 13 Tesla. MPL peak energies of two specimens were analyzed as a function of magnetic field. Up to four or five Landau levels (LLs) in CSs were resolved below the Fermi level. LLs were duty assigned to fit theoretical LL energies in nonparabolic CSs. Experimental LL energy differences in CSs, determined by infrared cyclotron resonance, were larger by about 6 meV than corresponding MPL peak energy difference. The difference was tentatively assigned to the difference in magneto-exciton binding energies, accompanied by LLs in CSs. The difference of binding energy changed like a kink with changing B and was possibly affected by valence band mixing at LLs. The effect of QW structure was discussed in relation to an impurity-related multiple exciton model.