Effects of band offset and nonparabolicity on the effective mass of two-dimensional electron gases in modulation-delta-doped Ga0.47In0.53As-based heterostructures

We present an investigation of electronic and optical properties of two-dimensional electron gases confined in modulation-delta-doped Ga0.47In0.53As-based heterostructures by Shubnikov-de Haas measurement and optically detected cyclotron resonance (ODCR). Quantum oscillations clearly show the occupation of the first two subbands. The Values of the effective masses obtained from ODCR measurements are considerably higher than the bulk data by 20-50 %. The theoretical prediction of the effect of nonparabolicity is insufficient to explain the experimental results. By choosing heterostructures with a very large difference in the conduction-band offset, we clearly show that this discrepancy can be attributed to the effect of wave-function penetration into the barrier material.