Far-Infrared Magneto-Absorption of Bound Excitons in Beryllium Doped Germanium

Abstract
A bound exciton is observed in far-infrared magnetoabsorption measurements of photo-excited beryllium doped germanium below 4.2 K. The absorption corresponds to the 1s to 2p± like transition of the electron in the bound exciton. Fifteen branches of peaks converge to about 3.4 meV at zero magnetic field. The 1s like ground state splits into more than two levels at zero magnetic field. The 2p± like excited state with an ionization energy of 1.7 meV is well described by the effective mass approximation.