Magnetospectroscopy to 30 T of donor states in InP

Far-infrared absorption spectroscopy in the energy range 100-400 cm-1 is reported for donors in indium phosphide at 4.2 K in magnetic fields of up to 30 T. Transitions are observed from the bound-electron ground state to both stable and metastable excited states in good agreement with the effective-mass theory. At the highest magnetic fields employed, corresponding to 2<γ<3, several absorption features are observed just above the TO-phonon energy, ∼5 effective Rydberg. These are attributed to the magnetopolaron interaction and cyclotron resonance