SPECTROSCOPIC STUDIES OF THE EFFECTS OF 2-DIMENSIONAL ELECTRON-GAS ON INTERBAND-TRANSITIONS

By using photoreflectance and photovoltaic spectra we have studied the behavior of two-dimensional electron gas in pseudomorphic high electronic mobility transistor structures. We find that the screening effect of two-dimensional electron gas on higher index subbands is much weaker than that on lower index subbands, and excitonic resonance is found to persist at the onset of the high-energy interband transition in both spectra despite the very large carrier concentration within the quantum well. In the meantime, band filling effects have different influences on the transition energy and strength at critical points for high and low temperature spectra, respectively. © 1995 American Institute of Physics.