The effect of low-energy GA IONS on GAAS/AIGAAS heterostructures

A high-mobility two-dimensional electron gas at a GaAs/AIGaAs heterojunction has been exposed to low-energy Ga ion beams. We report the reduction in both the sheet carrier density and mobility at 4 K for ion doses and energies in the range 101’-101’ cm-’ and 1-6 keV respectively. The sheet resistivity can be increased by a factor of 10” with a dose of 2 x 10” cm -’io ns at 6 keV. The ion irradiation also reduces the persistence of the low-temperature photo-induced conduction and increases the amount of ionised impurity scattering. Reduced photoluminescence from wells close to the surface of a multiple quantum well structure extends the transport data to suggest a range of ~ 7 n0m from the surface over which electronic properties are modified. An ultra-high vacuum compatible method for altering the surface electronic properties therefore seems viable.