Isolation of p-type carbon δ-doped layers in GaAs by ion bombardment

Abstract

The evolution of the sheet resistance (Rs) in δ-doped layers in GaAs during He ion irradiation was investigated. The Rs increases with the dose accumulation in a similar way that occurs in layers with much wider dopant profiles, produced either by ion implantation or epi-growth. The Rs becomes higher than 109 Ω/sq after the so-called threshold dose (Dth) is accumulated. The values of Dth closely correlate with the ratio of the estimated number of replacement collisions at the depth of the δ-doped layer and the original sheet hole concentration. The maximum thermal stability of the isolation, i.e. the persistence of Rs at values above 109 Ω/sq after a subsequent thermal annealing is of about 550–600 °C.