We report optically detected cyclotron resonance (ODCR) measurements on two subband occupied electronic systems confined in triangular and square quantum wells. It is shown that the ODCR measurement is a useful tool for the understanding of the luminescence processes, in addition to the characterization of carrier concentration, effective mass and Fermi energy. We find that only one broad photoluminescence (PL) line locates below the energy gap for the triangular well, which is attributed to donor-to-acceptor recombinations. For the square well, two lines with emission energies higher than the bandgap are observed. Each line width is consistent with the Fermi energy of the first and second subband. This suggests that the emissions involve electron transitions from the first and second subbands at all occupied k states to localized holes. We also find that the effective mass of electrons in the first subband is heavier than that of electrons in the second subband in the triangular well due to the effect of nonparabolicity and the electron distribution, while the reverse is observed in the square well. This is explained in part by the nonparabolicity and, significantly, by the barrier leakage of the electron wavefunction. Furthermore, we find that the single particle relaxation time obtained from magnetoresistance measurements and the scattering time from cyclotron resonance are longer for electrons in the upper subband for both triangular and square wells, and the relaxation time is smaller than the corresponding scattering time, consistent with previous transport results.

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