Electron effective mass determination in asymmetric modulation-doped field-effect transistor heterostructures using InxGa1−xAs quantum well and InAs–GaAs superlattice channels
Cyclotron resonance and photoluminescence measurements have been performed on two types of modulation-doped field-effect transistor heterostructures having their bidimensional channel based, respectively, on an InxGa1-xAs quantum well and an InAs-GaAs short-period superlattice. A linear dependence of the electron effective mass as a function of indium content of the channel was obtained from cyclotron resonance measurements. For a given average value of the indium content, the effective mass in the InAs-GaAs short-period superlattice channel is found to be systematically higher than that obtained in structures with an alloy-based channel. This is attributed to larger nonparabolic effects in the former case. In our theoretical model, the electron and heavy hole energy levels and the electron wavefunction are determined self-consistently and used to estimate the nonparabolic corrections that apply to the effective mass deduced from cyclotron resonance measurements.