OPTICALLY DETECTED IMPURITY D-0 AND D- TRANSITIONS IN GAAS QUANTUM-WELLS

We have carried out a far-infrared magnet-optical study on shallow don or states confined in GaAs quantum wells (QWs), applying a recently de veloped optical detection technique. We have observed, in addition to cyclotron resonance, the 1s --> 2p(+) transition of neutral donors (D- 0), and singlet and triplet transitions of negative donor ions (D-); t he latter observation verifies the existence of D- ions in well-only d oped QWs under optical pumping. This is the first observation of optic ally detected impurity resonances in confined systems and demonstrates the power and utility of this technique for such studies.