Infrared studies of the acceptor states in epitaxial films of GaAs

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Abstract
The far-infrared extrinsic photoconductivity of p-GaAs is investigated at frequencies up to 500 cm-1. Sharp lines corresponding to impurity transitions between bound hole states are observed between 120 and 240 cm-1, and the lowest three lines are identified with transitions from the ground (1S3/2) state to the 2P3/2, 2P5/2 ( Gamma 8) and 2P5/2 ( Gamma 7) states. The relative separation of these lines agrees extremely well with the values that Lipari and Baldereschi calculated using the theoretical band parameters of Lawaetz. The measurements may therefore be taken as a further verification of the valence band parameters for GaAs. From the absolute values of the impurity transitions, values were deduced for the chemical shifts and binding energies of the acceptors observed, one of which is known to be zinc.