Excited-state spectroscopy of confined shallow donor impurities in a multi-quantum well

Abstract
The far infrared (FIR) photoconductive response of silicon-doped GaAs/AlGaAs multi-quantum wells (MQWS) at 4.2 K reveals evidence of several transitions from the ground state to higher excited states of the confined impurity (e.g. 1s-3d+1, 1s-3p+1, 1s-3d+2, 1s-4d+2 etc.). Assignments are made by comparison with the bulk case and with available theory. Linewidths of the 1s-2p+ transition indicate that in the most favourable case minimum redistribution of the silicon dopant occurs which permits observation of higher state transitions.