High-energy transitions of shallow magnetodonors in a GaAs/Al0.3Ga0.7As multiple quantum well

The high-energy states of a shallow donor in a GaAs/Ga0.7Al0.3As multiple-q uantum-well structure subjected to a magnetic field in the growth direction are studied both theoretically and experimentally. Effects due to higher c onfinement subbands as well as due to the electron-phonon interaction are i nvestigated. We show that most of the peaks in the infrared photoconductivi ty spectrum are due to direct transitions from the ground state to the m = +/-1 magnetodonor states associated with the first subband, but transitions to the m = +/-1 states of the third subband are also apparent. The remaini ng photoconductivity peaks are explained by phonon-assisted impurity transi tions.