Degree Name

Doctor of Philosophy


Department of Engineering Physics


This dissertation reports on the far-infrared magnetospectroscopy of electron in a variety of GaAs-based semiconductors.

In the course of this investigation, a new far-infrared facility has been developed. This facility permits experiments under far-infrared radiation at low temperatures and with high magnetic fields.

Zero-field central-cell corrections of 0.110 meV and 0.059 meV have been determined for sulphur and silicon donor impurities, respectively, in bulk GaAs. These results, in magnetic fields of up to 39 T, greatly extend reported values for centralcell corrections, which were previously only available up to 6 T. Good agreement was found with theoretical calculations based on a hydrogenic model corrected for central cell effects.

A thorough search for the predicted magneto-photon-phonon resonance effect in a two-dimensional electron gas was carried out, using Fourier transform as well as laser spectroscopy. The proposed effect was not observed.

Extremely narrow cyclotron resonance linewidths (BCR/△B = 660) in a two-dimensional electron gas are reported. These measurements are made on an enhancement- mode field effect transistor. The top-gated architecture avoids the necessity of doping carriers into the sample. It also allows tuning of the electron density. Filling-factor-dependent oscillations in cyclotron resonance linewidth are observed up to 𝑣 = 8. This data challenges the usual explanation of impurity screening for these oscillations.

The first known far-infrared magneto-photoresponse has been measured in a quantum point contact. These samples also have a top-gated architecture, allowing a tunable electron density. Strong, carrier-concentration-dependent oscillations are observed in the region of the cyclotron resonance. These are attributed to resonant heating of the sample.