Abstract
An investigation of shallow donor energy levels in magnetic fields in the ternary alloy Ga0.47In0.53As, lattice matched to InP, has been made. Transitions between 1s and 2p energy levels of shallow hydrogenic donors have been observed in photoconductivity as a function of magnetic field. Transition energies and their magnetic field dependence are well predicted by the use of an effective Rydberg, however it is found that the 1s to 2p+ transition energy deviates from the theoretical value at high fields. This clearly indicates strong polaron pinning of the 2p+ level to two LO phonon modes which are 'GaAs'-like and 'InAs'-like, arising from the GaInAs.