Semiconductor quantum wells (QWs), quantum wires and quantum dots are currently of great interest, and optical and infrared (IR) techniques have been central to developing an understanding of the electronic states, excitations and interactions in these low-dimensional semiconductor structures. Optically detected resonance (ODR) spectroscopy, an approach which combines the sensitivity of visible/near IR photon detection with far IR excitation, and which alleviates many of the problems alluded to above, has recently been developed, and extended and used for the first time by the co-investigators to study neutral and negative donor ions in doped QW's and internal transitions of photocreated excitons in QWs. These results demonstrate the promise of ODR spectroscopy for studies of low-dimensional semiconductor structures.
Based on our experience with the conventional ODR approach and our recent demonstration experiments with a borrowed spectrograph/CCD array system, we will acquire a high sensitivity, high resolution mated spectrograph/CCD array system with acquisition and analysis software for full-spectrum ODR spectroscopy studies of semiconductor nanostructures. This system will be used to investigate several basic issues related to the electronic states of low-dimensional semiconductor structures in high magnetic fields. The project involves the collaboration of two senior investigators whose combined expertise spans optical studies of low-dimensional semiconductor structures in the III-V and II-VI materials systems from the far IR to the visible. Specific problems to be investigated include: internal states of negatively and positively charged excitons and cyclotron resonance of charged excitons; effects of excess electrons and holes on the excitonic states and the metal-insulator transition; many-body effects in the integer and fractional quantum Hall effect regimes; and application of ODR to the study of impurity and free carrier electronic states in quantum wires and quantum dots. We anticipate that the proposed system will greatly enhance both the quantity and quality of these experiments, and the education and training of our students. %%% ***
