Electrical isolation of p-type GaAs layers by ion irradiation

Abstract

The electrical isolation of p-type GaAs layers doped with acceptor impurities incorporated in the Ga sublattice (Mg) or As sublattice (C) was studied using proton bombardment. It was found that practically the same proton dose is required to reach complete isolation (isolation threshold dose, Dth) in layers doped with either Mg or C of comparable original sheet hole concentration (ps). This result is evidence that the sublattice where the acceptor dopant atoms are incorporated does not play any significant role for the isolation formation process in GaAs. The behavior of the recovery of the conductivity during subsequent thermal annealing was found very similar in Mg and C doped samples irradiated to equal proton doses. In samples irradiated to doses <Dth, the sheet resistance (Rs) increases during annealing at temperatures >100°C, reaches a maximum at ~≈200°C, and then decreases progressively toward the original value. For proton doses ranging from Dth to 5Dth , the isolation is preserved up to the temperature of ~≈500°C. The temperature of ~≈700°C was found to be the upper limit for the thermal stability of the isolation in samples irradiated to doses of 100 Dth.